diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index a48dfbc335..5a08f46559 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -3,7 +3,6 @@
 module checker
 
 import os
-import time
 import v.ast
 import v.vmod
 import v.token
@@ -46,15 +45,21 @@ pub struct Checker {
 pub mut:
 	pref &pref.Preferences = unsafe { nil } // Preferences shared from V struct
 	//
-	table                      &ast.Table = unsafe { nil }
-	file                       &ast.File  = unsafe { nil }
-	nr_errors                  int
-	nr_warnings                int
-	nr_notices                 int
-	errors                     []errors.Error
-	warnings                   []errors.Warning
-	notices                    []errors.Notice
-	error_lines                []int // to avoid printing multiple errors for the same line
+	table &ast.Table = unsafe { nil }
+	file  &ast.File  = unsafe { nil }
+	//
+	nr_errors     int
+	nr_warnings   int
+	nr_notices    int
+	errors        []errors.Error
+	warnings      []errors.Warning
+	notices       []errors.Notice
+	error_lines   map[string]bool // dedup errors
+	warning_lines map[string]bool // dedup warns
+	notice_lines  map[string]bool // dedup notices
+	error_details []string
+	should_abort  bool // when too many errors/warnings/notices are accumulated, .should_abort becomes true. It is checked in statement/expression loops, so the checker can return early, instead of wasting time.
+	//
 	expected_type              ast.Type
 	expected_or_type           ast.Type        // fn() or { 'this type' } eg. string. expected or block type
 	expected_expr_type         ast.Type        // if/match is_expr: expected_type
@@ -66,7 +71,6 @@ pub mut:
 	locked_names               []string // vars that are currently locked
 	rlocked_names              []string // vars that are currently read-locked
 	in_for_count               int      // if checker is currently in a for loop
-	should_abort               bool     // when too many errors/warnings/notices are accumulated, .should_abort becomes true. It is checked in statement/expression loops, so the checker can return early, instead of wasting time.
 	returns                    bool
 	scope_returns              bool
 	is_builtin_mod             bool // true inside the 'builtin', 'os' or 'strconv' modules; TODO: remove the need for special casing this
@@ -100,7 +104,6 @@ mut:
 	ensure_generic_type_level        int // to avoid infinite recursion segfaults in ensure_generic_type_specify_type_names
 	cur_orm_ts                       ast.TypeSymbol
 	cur_anon_fn                      &ast.AnonFn = unsafe { nil }
-	error_details                    []string
 	vmod_file_content                string     // needed for @VMOD_FILE, contents of the file, *NOT its path**
 	loop_label                       string     // set when inside a labelled for loop
 	vweb_gen_types                   []ast.Type // vweb route checks
@@ -176,6 +179,7 @@ fn (mut c Checker) reset_checker_state_at_start_of_new_file() {
 	c.inside_casting_to_str = false
 	c.inside_decl_rhs = false
 	c.inside_if_guard = false
+	c.error_details.clear()
 }
 
 pub fn (mut c Checker) check(mut ast_file ast.File) {
@@ -4531,47 +4535,6 @@ fn (mut c Checker) check_dup_keys(node &ast.MapInit, i int) {
 	}
 }
 
-// call this *before* calling error or warn
-fn (mut c Checker) add_error_detail(s string) {
-	c.error_details << s
-}
-
-fn (mut c Checker) add_error_detail_with_pos(msg string, pos token.Pos) {
-	c.add_error_detail(util.formatted_error('details:', msg, c.file.path, pos))
-}
-
-fn (mut c Checker) add_instruction_for_option_type() {
-	c.add_error_detail_with_pos('prepend ? before the declaration of the return type of `${c.table.cur_fn.name}`',
-		c.table.cur_fn.return_type_pos)
-}
-
-fn (mut c Checker) add_instruction_for_result_type() {
-	c.add_error_detail_with_pos('prepend ! before the declaration of the return type of `${c.table.cur_fn.name}`',
-		c.table.cur_fn.return_type_pos)
-}
-
-fn (mut c Checker) warn(s string, pos token.Pos) {
-	allow_warnings := !(c.pref.is_prod || c.pref.warns_are_errors) // allow warnings only in dev builds
-	c.warn_or_error(s, pos, allow_warnings)
-}
-
-fn (mut c Checker) error(message string, pos token.Pos) {
-	$if checker_exit_on_first_error ? {
-		eprintln('\n\n>> checker error: ${message}, pos: ${pos}')
-		print_backtrace()
-		exit(1)
-	}
-	if (c.pref.translated || c.file.is_translated) && message.starts_with('mismatched types') {
-		// TODO move this
-		return
-	}
-	if c.pref.is_verbose {
-		print_backtrace()
-	}
-	msg := message.replace('`Array_', '`[]')
-	c.warn_or_error(msg, pos, false)
-}
-
 fn (c &Checker) check_struct_signature_init_fields(from ast.Struct, to ast.Struct, node ast.StructInit) bool {
 	if node.init_fields.len == 0 {
 		return from.fields.len == to.fields.len
@@ -4617,96 +4580,6 @@ fn (c &Checker) check_struct_signature(from ast.Struct, to ast.Struct) bool {
 	return true
 }
 
-fn (mut c Checker) note(message string, pos token.Pos) {
-	if c.pref.message_limit >= 0 && c.nr_notices >= c.pref.message_limit {
-		c.should_abort = true
-		return
-	}
-	if c.is_generated {
-		return
-	}
-	if c.pref.notes_are_errors {
-		c.error(message, pos)
-	}
-	mut details := ''
-	if c.error_details.len > 0 {
-		details = c.error_details.join('\n')
-		c.error_details = []
-	}
-	wrn := errors.Notice{
-		reporter: errors.Reporter.checker
-		pos: pos
-		file_path: c.file.path
-		message: message
-		details: details
-	}
-	c.file.notices << wrn
-	c.notices << wrn
-	c.nr_notices++
-}
-
-fn (mut c Checker) warn_or_error(message string, pos token.Pos, warn bool) {
-	// add backtrace to issue struct, how?
-	// if c.pref.is_verbose {
-	// print_backtrace()
-	// }
-	mut details := ''
-	if c.error_details.len > 0 {
-		details = c.error_details.join('\n')
-		c.error_details = []
-	}
-	if warn && !c.pref.skip_warnings {
-		c.nr_warnings++
-		if c.pref.message_limit >= 0 && c.nr_warnings >= c.pref.message_limit {
-			c.should_abort = true
-			return
-		}
-		wrn := errors.Warning{
-			reporter: errors.Reporter.checker
-			pos: pos
-			file_path: c.file.path
-			message: message
-			details: details
-		}
-		c.file.warnings << wrn
-		c.warnings << wrn
-		return
-	}
-	if !warn {
-		if c.pref.fatal_errors {
-			util.show_compiler_message('error:', errors.CompilerMessage{
-				pos: pos
-				file_path: c.file.path
-				message: message
-				details: details
-			})
-			exit(1)
-		}
-		c.nr_errors++
-		if c.pref.message_limit >= 0 && c.errors.len >= c.pref.message_limit {
-			c.should_abort = true
-			return
-		}
-		if pos.line_nr !in c.error_lines {
-			err := errors.Error{
-				reporter: errors.Reporter.checker
-				pos: pos
-				file_path: c.file.path
-				message: message
-				details: details
-			}
-			c.file.errors << err
-			c.errors << err
-			c.error_lines << pos.line_nr
-		}
-	}
-}
-
-// for debugging only
-fn (c &Checker) fileis(s string) bool {
-	return c.file.path.contains(s)
-}
-
 fn (mut c Checker) fetch_field_name(field ast.StructField) string {
 	mut name := field.name
 	for attr in field.attrs {
@@ -4722,12 +4595,6 @@ fn (mut c Checker) fetch_field_name(field ast.StructField) string {
 	return name
 }
 
-fn (mut c Checker) trace[T](fbase string, x &T) {
-	if c.file.path_base == fbase {
-		println('> c.trace | ${fbase:-10s} | ${x}')
-	}
-}
-
 fn (mut c Checker) ensure_generic_type_specify_type_names(typ ast.Type, pos token.Pos) bool {
 	if typ == 0 {
 		c.error('unknown type', pos)
@@ -5013,45 +4880,6 @@ fn (mut c Checker) check_unused_labels() {
 	}
 }
 
-fn (mut c Checker) deprecate(kind string, name string, attrs []ast.Attr, pos token.Pos) {
-	mut deprecation_message := ''
-	now := time.now()
-	mut after_time := now
-	for attr in attrs {
-		if attr.name == 'deprecated' && attr.arg != '' {
-			deprecation_message = attr.arg
-		}
-		if attr.name == 'deprecated_after' && attr.arg != '' {
-			after_time = time.parse_iso8601(attr.arg) or {
-				c.error('invalid time format', attr.pos)
-				now
-			}
-		}
-	}
-	start_message := '${kind} `${name}`'
-	error_time := after_time.add_days(180)
-	if error_time < now {
-		c.error(semicolonize('${start_message} has been deprecated since ${after_time.ymmdd()}',
-			deprecation_message), pos)
-	} else if after_time < now {
-		c.warn(semicolonize('${start_message} has been deprecated since ${after_time.ymmdd()}, it will be an error after ${error_time.ymmdd()}',
-			deprecation_message), pos)
-	} else if after_time == now {
-		c.warn(semicolonize('${start_message} has been deprecated', deprecation_message),
-			pos)
-	} else {
-		c.note(semicolonize('${start_message} will be deprecated after ${after_time.ymmdd()}, and will become an error after ${error_time.ymmdd()}',
-			deprecation_message), pos)
-	}
-}
-
-fn semicolonize(main string, details string) string {
-	if details == '' {
-		return main
-	}
-	return '${main}; ${details}'
-}
-
 fn (mut c Checker) deprecate_old_isreftype_and_sizeof_of_a_guessed_type(is_guessed_type bool, typ ast.Type, pos token.Pos, label string) {
 	if is_guessed_type {
 		styp := c.table.type_to_str(typ)
diff --git a/vlib/v/checker/errors.v b/vlib/v/checker/errors.v
new file mode 100644
index 0000000000..3e0e7a3e17
--- /dev/null
+++ b/vlib/v/checker/errors.v
@@ -0,0 +1,195 @@
+// Copyright (c) 2019-2023 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license that can be found in the LICENSE file.
+module checker
+
+import time
+import v.ast
+import v.token
+import v.errors
+import v.util
+
+// call this *before* calling error or warn
+fn (mut c Checker) add_error_detail(s string) {
+	c.error_details << s
+}
+
+fn (mut c Checker) add_error_detail_with_pos(msg string, pos token.Pos) {
+	c.add_error_detail(util.formatted_error('details:', msg, c.file.path, pos))
+}
+
+fn (mut c Checker) add_instruction_for_option_type() {
+	c.add_error_detail_with_pos('prepend ? before the declaration of the return type of `${c.table.cur_fn.name}`',
+		c.table.cur_fn.return_type_pos)
+}
+
+fn (mut c Checker) add_instruction_for_result_type() {
+	c.add_error_detail_with_pos('prepend ! before the declaration of the return type of `${c.table.cur_fn.name}`',
+		c.table.cur_fn.return_type_pos)
+}
+
+fn (mut c Checker) warn(s string, pos token.Pos) {
+	allow_warnings := !(c.pref.is_prod || c.pref.warns_are_errors) // allow warnings only in dev builds
+	c.warn_or_error(s, pos, allow_warnings)
+}
+
+fn (mut c Checker) error(message string, pos token.Pos) {
+	if (c.pref.translated || c.file.is_translated) && message.starts_with('mismatched types') {
+		// TODO move this
+		return
+	}
+	msg := message.replace('`Array_', '`[]')
+	c.warn_or_error(msg, pos, false)
+}
+
+fn (mut c Checker) note(message string, pos token.Pos) {
+	if c.pref.message_limit >= 0 && c.nr_notices >= c.pref.message_limit {
+		c.should_abort = true
+		return
+	}
+	if c.is_generated {
+		return
+	}
+	if c.pref.notes_are_errors {
+		c.error(message, pos)
+	}
+	mut details := ''
+	if c.error_details.len > 0 {
+		details = c.error_details.join('\n')
+		c.error_details = []
+	}
+	// deduplicate notices for the same line
+	kpos := '${c.file.path}:${pos.line_nr}:${message}'
+	if kpos !in c.notice_lines {
+		c.notice_lines[kpos] = true
+		note := errors.Notice{
+			reporter: errors.Reporter.checker
+			pos: pos
+			file_path: c.file.path
+			message: message
+			details: details
+		}
+		c.file.notices << note
+		c.notices << note
+		c.nr_notices++
+	}
+}
+
+fn (mut c Checker) warn_or_error(message string, pos token.Pos, warn bool) {
+	if !warn {
+		$if checker_exit_on_first_error ? {
+			eprintln('\n\n>> checker error: ${message}, pos: ${pos}')
+			print_backtrace()
+			exit(1)
+		}
+		if c.pref.is_verbose {
+			print_backtrace()
+		}
+	}
+	mut details := ''
+	if c.error_details.len > 0 {
+		details = c.error_details.join('\n')
+		c.error_details = []
+	}
+	if warn && !c.pref.skip_warnings {
+		c.nr_warnings++
+		if c.pref.message_limit >= 0 && c.nr_warnings >= c.pref.message_limit {
+			c.should_abort = true
+			return
+		}
+		// deduplicate warnings for the same line
+		kpos := '${c.file.path}:${pos.line_nr}:${message}'
+		if kpos !in c.warning_lines {
+			c.warning_lines[kpos] = true
+			wrn := errors.Warning{
+				reporter: errors.Reporter.checker
+				pos: pos
+				file_path: c.file.path
+				message: message
+				details: details
+			}
+			c.file.warnings << wrn
+			c.warnings << wrn
+		}
+		return
+	}
+	if !warn {
+		if c.pref.fatal_errors {
+			util.show_compiler_message('error:', errors.CompilerMessage{
+				pos: pos
+				file_path: c.file.path
+				message: message
+				details: details
+			})
+			exit(1)
+		}
+		c.nr_errors++
+		if c.pref.message_limit >= 0 && c.errors.len >= c.pref.message_limit {
+			c.should_abort = true
+			return
+		}
+		// deduplicate errors for the same line
+		kpos := '${c.file.path}:${pos.line_nr}:${message}'
+		if kpos !in c.error_lines {
+			c.error_lines[kpos] = true
+			err := errors.Error{
+				reporter: errors.Reporter.checker
+				pos: pos
+				file_path: c.file.path
+				message: message
+				details: details
+			}
+			c.file.errors << err
+			c.errors << err
+		}
+	}
+}
+
+// for debugging only
+fn (c &Checker) fileis(s string) bool {
+	return c.file.path.contains(s)
+}
+
+fn (mut c Checker) trace[T](fbase string, x &T) {
+	if c.file.path_base == fbase {
+		println('> c.trace | ${fbase:-10s} | ${x}')
+	}
+}
+
+fn (mut c Checker) deprecate(kind string, name string, attrs []ast.Attr, pos token.Pos) {
+	mut deprecation_message := ''
+	now := time.now()
+	mut after_time := now
+	for attr in attrs {
+		if attr.name == 'deprecated' && attr.arg != '' {
+			deprecation_message = attr.arg
+		}
+		if attr.name == 'deprecated_after' && attr.arg != '' {
+			after_time = time.parse_iso8601(attr.arg) or {
+				c.error('invalid time format', attr.pos)
+				now
+			}
+		}
+	}
+	start_message := '${kind} `${name}`'
+	error_time := after_time.add_days(180)
+	if error_time < now {
+		c.error(semicolonize('${start_message} has been deprecated since ${after_time.ymmdd()}',
+			deprecation_message), pos)
+	} else if after_time < now {
+		c.warn(semicolonize('${start_message} has been deprecated since ${after_time.ymmdd()}, it will be an error after ${error_time.ymmdd()}',
+			deprecation_message), pos)
+	} else if after_time == now {
+		c.warn(semicolonize('${start_message} has been deprecated', deprecation_message),
+			pos)
+	} else {
+		c.note(semicolonize('${start_message} will be deprecated after ${after_time.ymmdd()}, and will become an error after ${error_time.ymmdd()}',
+			deprecation_message), pos)
+	}
+}
+
+fn semicolonize(main string, details string) string {
+	if details == '' {
+		return main
+	}
+	return '${main}; ${details}'
+}
diff --git a/vlib/v/checker/tests/add_op_wrong_type_err.out b/vlib/v/checker/tests/add_op_wrong_type_err.out
index c1c8699172..123ddc36e3 100644
--- a/vlib/v/checker/tests/add_op_wrong_type_err.out
+++ b/vlib/v/checker/tests/add_op_wrong_type_err.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/add_op_wrong_type_err.vv:3:13: error: mismatched types `Aaa
       |             ~~~~~~~~~~
     4 |     println(10 + Aaa{})
     5 |     println([1,2,3] + 10)
+vlib/v/checker/tests/add_op_wrong_type_err.vv:3:13: error: infix expr: cannot use `int literal` (right expression) as `Aaa`
+    1 | struct Aaa{}
+    2 | fn main() {
+    3 |     println(Aaa{} + 10)
+      |             ~~~~~~~~~~
+    4 |     println(10 + Aaa{})
+    5 |     println([1,2,3] + 10)
 vlib/v/checker/tests/add_op_wrong_type_err.vv:4:13: error: mismatched types `int literal` and `Aaa`
     2 | fn main() {
     3 |     println(Aaa{} + 10)
@@ -12,6 +19,13 @@ vlib/v/checker/tests/add_op_wrong_type_err.vv:4:13: error: mismatched types `int
       |             ~~~~~~~~~~
     5 |     println([1,2,3] + 10)
     6 |     println(10 + [1,2,3])
+vlib/v/checker/tests/add_op_wrong_type_err.vv:4:13: error: infix expr: cannot use `Aaa` (right expression) as `int literal`
+    2 | fn main() {
+    3 |     println(Aaa{} + 10)
+    4 |     println(10 + Aaa{})
+      |             ~~~~~~~~~~
+    5 |     println([1,2,3] + 10)
+    6 |     println(10 + [1,2,3])
 vlib/v/checker/tests/add_op_wrong_type_err.vv:5:13: error: mismatched types `[]int` and `int literal`
     3 |     println(Aaa{} + 10)
     4 |     println(10 + Aaa{})
@@ -19,6 +33,13 @@ vlib/v/checker/tests/add_op_wrong_type_err.vv:5:13: error: mismatched types `[]i
       |             ~~~~~~~~~~~~
     6 |     println(10 + [1,2,3])
     7 |     a := map[string]int
+vlib/v/checker/tests/add_op_wrong_type_err.vv:5:13: error: infix expr: cannot use `int literal` (right expression) as `[]int`
+    3 |     println(Aaa{} + 10)
+    4 |     println(10 + Aaa{})
+    5 |     println([1,2,3] + 10)
+      |             ~~~~~~~~~~~~
+    6 |     println(10 + [1,2,3])
+    7 |     a := map[string]int
 vlib/v/checker/tests/add_op_wrong_type_err.vv:6:13: error: mismatched types `int literal` and `[]int`
     4 |     println(10 + Aaa{})
     5 |     println([1,2,3] + 10)
@@ -26,6 +47,13 @@ vlib/v/checker/tests/add_op_wrong_type_err.vv:6:13: error: mismatched types `int
       |             ~~~~~~~~~~~~
     7 |     a := map[string]int
     8 |     println(a + 10)
+vlib/v/checker/tests/add_op_wrong_type_err.vv:6:13: error: infix expr: cannot use `[]int` (right expression) as `int literal`
+    4 |     println(10 + Aaa{})
+    5 |     println([1,2,3] + 10)
+    6 |     println(10 + [1,2,3])
+      |             ~~~~~~~~~~~~
+    7 |     a := map[string]int
+    8 |     println(a + 10)
 vlib/v/checker/tests/add_op_wrong_type_err.vv:8:13: error: mismatched types `map[string]int` and `int literal`
     6 |     println(10 + [1,2,3])
     7 |     a := map[string]int
@@ -33,10 +61,22 @@ vlib/v/checker/tests/add_op_wrong_type_err.vv:8:13: error: mismatched types `map
       |             ~~~~~~
     9 |     println(10 + a)
    10 | }
+vlib/v/checker/tests/add_op_wrong_type_err.vv:8:13: error: infix expr: cannot use `int literal` (right expression) as `map[string]int`
+    6 |     println(10 + [1,2,3])
+    7 |     a := map[string]int
+    8 |     println(a + 10)
+      |             ~~~~~~
+    9 |     println(10 + a)
+   10 | }
 vlib/v/checker/tests/add_op_wrong_type_err.vv:9:13: error: mismatched types `int literal` and `map[string]int`
     7 |     a := map[string]int
     8 |     println(a + 10)
     9 |     println(10 + a)
       |             ~~~~~~
    10 | }
-
+vlib/v/checker/tests/add_op_wrong_type_err.vv:9:13: error: infix expr: cannot use `map[string]int` (right expression) as `int literal`
+    7 |     a := map[string]int
+    8 |     println(a + 10)
+    9 |     println(10 + a)
+      |             ~~~~~~
+   10 | }
diff --git a/vlib/v/checker/tests/ambiguous_field_method_err.out b/vlib/v/checker/tests/ambiguous_field_method_err.out
index 31a7360d5e..9360bb6b90 100644
--- a/vlib/v/checker/tests/ambiguous_field_method_err.out
+++ b/vlib/v/checker/tests/ambiguous_field_method_err.out
@@ -11,9 +11,29 @@ vlib/v/checker/tests/ambiguous_field_method_err.vv:22:4: error: ambiguous method
       |       ~~~~~~
    23 |     n := b.name
    24 | }
+vlib/v/checker/tests/ambiguous_field_method_err.vv:22:4: error: unknown method or field: `Bar.test`
+   20 | fn main() {
+   21 |     b := Bar{}
+   22 |     b.test()
+      |       ~~~~~~
+   23 |     n := b.name
+   24 | }
 vlib/v/checker/tests/ambiguous_field_method_err.vv:23:9: error: ambiguous field `name`
    21 |     b := Bar{}
    22 |     b.test()
    23 |     n := b.name
       |            ~~~~
    24 | }
+vlib/v/checker/tests/ambiguous_field_method_err.vv:23:9: error: type `Bar` has no field named `name`.
+2 possibilities: `Foo2`, `Foo`.
+   21 |     b := Bar{}
+   22 |     b.test()
+   23 |     n := b.name
+      |            ~~~~
+   24 | }
+vlib/v/checker/tests/ambiguous_field_method_err.vv:23:4: error: assignment mismatch: 1 variable(s) 0 value(s)
+   21 |     b := Bar{}
+   22 |     b.test()
+   23 |     n := b.name
+      |       ~~
+   24 | }
diff --git a/vlib/v/checker/tests/ambiguous_function_call.out b/vlib/v/checker/tests/ambiguous_function_call.out
index b88ef1a440..cd4e22ee55 100644
--- a/vlib/v/checker/tests/ambiguous_function_call.out
+++ b/vlib/v/checker/tests/ambiguous_function_call.out
@@ -11,3 +11,10 @@ vlib/v/checker/tests/ambiguous_function_call.vv:7:2: error: ambiguous call to: `
       |     ~~~~~~~~~~
     8 | }
     9 |
+vlib/v/checker/tests/ambiguous_function_call.vv:7:7: error: expected 0 arguments, but got 1
+    5 | fn foo2() {
+    6 |     foo2 := 1
+    7 |     foo2(foo2)
+      |          ~~~~
+    8 | }
+    9 |
diff --git a/vlib/v/checker/tests/anon_fn_arg_type_err.out b/vlib/v/checker/tests/anon_fn_arg_type_err.out
index af0fb10383..0f283dceaf 100644
--- a/vlib/v/checker/tests/anon_fn_arg_type_err.out
+++ b/vlib/v/checker/tests/anon_fn_arg_type_err.out
@@ -12,6 +12,20 @@ vlib/v/checker/tests/anon_fn_arg_type_err.vv:7:10: error: `i` must be added to t
       |                ^
     8 |     }
     9 |
+vlib/v/checker/tests/anon_fn_arg_type_err.vv:7:3: error: `i` used as value
+    5 | 
+    6 |     func := fn (i) int {
+    7 |         return i
+      |         ~~~~~~~~
+    8 |     }
+    9 |
+vlib/v/checker/tests/anon_fn_arg_type_err.vv:6:14: error: unknown type `i`
+    4 |     mut i := 1
+    5 | 
+    6 |     func := fn (i) int {
+      |                 ^
+    7 |         return i
+    8 |     }
 vlib/v/checker/tests/anon_fn_arg_type_err.vv:10:15: error: cannot use `int` as `i` in argument 1 to `func`
     8 |     }
     9 | 
diff --git a/vlib/v/checker/tests/any_int_float_ban_err.out b/vlib/v/checker/tests/any_int_float_ban_err.out
index 510ab1856a..0d353e5bda 100644
--- a/vlib/v/checker/tests/any_int_float_ban_err.out
+++ b/vlib/v/checker/tests/any_int_float_ban_err.out
@@ -3,14 +3,19 @@ vlib/v/checker/tests/any_int_float_ban_err.vv:1:12: error: unknown type `int_lit
       |            ~~~~~~~~~~~
     2 | type Fo2 = int_literal
     3 |
+vlib/v/checker/tests/any_int_float_ban_err.vv:1:26: error: unknown type `float_literal`
+    1 | type Foo = int_literal | float_literal
+      |                          ~~~~~~~~~~~~~
+    2 | type Fo2 = int_literal
+    3 |
 vlib/v/checker/tests/any_int_float_ban_err.vv:2:12: error: unknown type `int_literal`
     1 | type Foo = int_literal | float_literal
     2 | type Fo2 = int_literal
       |            ~~~~~~~~~~~
-    3 |
+    3 | 
     4 | struct Int {
 vlib/v/checker/tests/any_int_float_ban_err.vv:5:7: error: unknown type `int_literal`
-    3 |
+    3 | 
     4 | struct Int {
     5 |     i int_literal
       |       ~~~~~~~~~~~
@@ -25,14 +30,14 @@ vlib/v/checker/tests/any_int_float_ban_err.vv:6:7: error: unknown type `float_li
     8 |
 vlib/v/checker/tests/any_int_float_ban_err.vv:9:10: error: unknown type `int_literal`
     7 | }
-    8 |
+    8 | 
     9 | fn foo(i int_literal) int_literal {
       |          ~~~~~~~~~~~
    10 |     return i
    11 | }
 vlib/v/checker/tests/any_int_float_ban_err.vv:13:11: error: unknown type `int_literal`
    11 | }
-   12 |
+   12 | 
    13 | fn foo2() int_literal {
       |           ~~~~~~~~~~~
    14 |     return 1
diff --git a/vlib/v/checker/tests/append_err.out b/vlib/v/checker/tests/append_err.out
index 4c87f24ef2..faabf2cbc6 100644
--- a/vlib/v/checker/tests/append_err.out
+++ b/vlib/v/checker/tests/append_err.out
@@ -18,3 +18,15 @@ vlib/v/checker/tests/append_err.vv:6:9: error: array append cannot be used in an
     6 |     _ = (l << 3).len
       |            ~~
     7 | }
+vlib/v/checker/tests/append_err.vv:6:15: error: `(l << 3)` does not return a value
+    4 |     
+    5 |     _ = l << 3
+    6 |     _ = (l << 3).len
+      |                  ~~~
+    7 | }
+vlib/v/checker/tests/append_err.vv:6:4: error: assignment mismatch: 1 variable(s) 0 value(s)
+    4 |     
+    5 |     _ = l << 3
+    6 |     _ = (l << 3).len
+      |       ^
+    7 | }
diff --git a/vlib/v/checker/tests/array_builtin_method_args_err.out b/vlib/v/checker/tests/array_builtin_method_args_err.out
index db760305c3..45313a393e 100644
--- a/vlib/v/checker/tests/array_builtin_method_args_err.out
+++ b/vlib/v/checker/tests/array_builtin_method_args_err.out
@@ -1,28 +1,35 @@
 vlib/v/checker/tests/array_builtin_method_args_err.vv:4:18: error: `.clone()` does not have any arguments
     2 |     arr := [1, 2, 3]
-    3 |
+    3 | 
     4 |     a1 := arr.clone(22)
       |                     ~~
     5 |     println(a1)
     6 |
 vlib/v/checker/tests/array_builtin_method_args_err.vv:7:18: error: `.first()` does not have any arguments
     5 |     println(a1)
-    6 |
+    6 | 
     7 |     a2 := arr.first('a2')
       |                     ~~~~
     8 |     println(a2)
     9 |
 vlib/v/checker/tests/array_builtin_method_args_err.vv:10:17: error: `.last()` does not have any arguments
     8 |     println(a2)
-    9 |
+    9 | 
    10 |     a3 := arr.last(1)
       |                    ^
    11 |     println(a3)
    12 |
 vlib/v/checker/tests/array_builtin_method_args_err.vv:13:16: error: `.pop()` does not have any arguments
    11 |     println(a3)
-   12 |
+   12 | 
    13 |     a4 := arr.pop(2)
       |                   ^
    14 |     println(a4)
    15 | }
+vlib/v/checker/tests/array_builtin_method_args_err.vv:13:8: error: `arr` is immutable, declare it with `mut` to make it mutable
+   11 |     println(a3)
+   12 | 
+   13 |     a4 := arr.pop(2)
+      |           ~~~
+   14 |     println(a4)
+   15 | }
diff --git a/vlib/v/checker/tests/array_filter_map_option_function_err.out b/vlib/v/checker/tests/array_filter_map_option_function_err.out
index eb4e34805b..de71105caa 100644
--- a/vlib/v/checker/tests/array_filter_map_option_function_err.out
+++ b/vlib/v/checker/tests/array_filter_map_option_function_err.out
@@ -1,21 +1,28 @@
 vlib/v/checker/tests/array_filter_map_option_function_err.vv:14:25: error: option needs to be unwrapped before using it in map/filter
    12 |     }
-   13 |
+   13 | 
    14 |     arr_struct2 := arr.map(option_mapping_struct)
       |                            ~~~~~~~~~~~~~~~~~~~~~
    15 |     println(arr_struct2)
    16 |
 vlib/v/checker/tests/array_filter_map_option_function_err.vv:17:18: error: option needs to be unwrapped before using it in map/filter
    15 |     println(arr_struct2)
-   16 |
+   16 | 
    17 |     arr_int2 := arr.map(option_mapping_int)
       |                     ~~~~~~~~~~~~~~~~~~~~~~~
    18 |     println(arr_int2)
    19 |
 vlib/v/checker/tests/array_filter_map_option_function_err.vv:20:20: error: option needs to be unwrapped before using it in map/filter
    18 |     println(arr_int2)
-   19 |
+   19 | 
    20 |     arr_filter := arr.filter(option_mapping_int)
       |                       ~~~~~~~~~~~~~~~~~~~~~~~~~~
    21 |     println(arr_filter)
-   22 | }
\ No newline at end of file
+   22 | }
+vlib/v/checker/tests/array_filter_map_option_function_err.vv:20:27: error: type mismatch, should use `fn(a int) bool {...}`
+   18 |     println(arr_int2)
+   19 | 
+   20 |     arr_filter := arr.filter(option_mapping_int)
+      |                              ~~~~~~~~~~~~~~~~~~
+   21 |     println(arr_filter)
+   22 | }
diff --git a/vlib/v/checker/tests/array_init_option_err.out b/vlib/v/checker/tests/array_init_option_err.out
index 14412c4b41..c8981286fd 100644
--- a/vlib/v/checker/tests/array_init_option_err.out
+++ b/vlib/v/checker/tests/array_init_option_err.out
@@ -4,25 +4,30 @@ vlib/v/checker/tests/array_init_option_err.vv:2:38: error: cannot use unwrapped
       |                                         ~~~~~
     3 |     dump(arr1)
     4 |
-vlib/v/checker/tests/array_init_option_err.vv:5:20: error: cannot use unwrapped Option as length
+vlib/v/checker/tests/array_init_option_err.vv:2:25: error: cannot use unwrapped Option as length
+    1 | fn main() {
+    2 |     mut arr1 := []int{len: get(), init: get()}
+      |                            ~~~~~
     3 |     dump(arr1)
     4 |
+vlib/v/checker/tests/array_init_option_err.vv:5:20: error: cannot use unwrapped Option as length
+    3 |     dump(arr1)
+    4 | 
     5 |     arr1 = []int{len: get(), init: get()?}
       |                       ~~~~~
     6 |     dump(arr1)
     7 |
 vlib/v/checker/tests/array_init_option_err.vv:8:34: error: cannot use unwrapped Option as initializer
     6 |     dump(arr1)
-    7 |
+    7 | 
     8 |     arr1 = []int{len: get()?, init: get()}
       |                                     ~~~~~
     9 |     dump(arr1)
    10 |
 vlib/v/checker/tests/array_init_option_err.vv:11:20: error: cannot use unwrapped Option as capacity
     9 |     dump(arr1)
-   10 |
+   10 | 
    11 |     arr1 = []int{cap: get(), len: get()?, init: get()?}
       |                       ~~~~~
    12 |     dump(arr1)
    13 | }
-
diff --git a/vlib/v/checker/tests/array_literal_modify_err.out b/vlib/v/checker/tests/array_literal_modify_err.out
index eaec4f986f..5629db6762 100644
--- a/vlib/v/checker/tests/array_literal_modify_err.out
+++ b/vlib/v/checker/tests/array_literal_modify_err.out
@@ -4,6 +4,12 @@ vlib/v/checker/tests/array_literal_modify_err.vv:2:24: error: array append canno
       |                           ~~
     3 |     println(nums)
     4 | }
+vlib/v/checker/tests/array_literal_modify_err.vv:2:14: error: array literal can not be modified
+    1 | fn main() {
+    2 |     mut nums := [1, 2, 3] << 4
+      |                 ~~~~~~~~~
+    3 |     println(nums)
+    4 | }
 vlib/v/checker/tests/array_literal_modify_err.vv:3:2: error: `println` can not print void expressions
     1 | fn main() {
     2 |     mut nums := [1, 2, 3] << 4
diff --git a/vlib/v/checker/tests/array_sort_err.out b/vlib/v/checker/tests/array_sort_err.out
index 04c3dbf8f3..ad876660bb 100644
--- a/vlib/v/checker/tests/array_sort_err.out
+++ b/vlib/v/checker/tests/array_sort_err.out
@@ -25,3 +25,15 @@ vlib/v/checker/tests/array_sort_err.vv:6:9: error: `.sort()` can only use `a` or
     6 |     arr.sort(c > d)
       |         ~~~~~~~~~~~
     7 | }
+vlib/v/checker/tests/array_sort_err.vv:6:14: error: undefined ident: `c`
+    4 |     arr.sort(a == b)
+    5 |     arr.sort(a > a)
+    6 |     arr.sort(c > d)
+      |              ^
+    7 | }
+vlib/v/checker/tests/array_sort_err.vv:6:18: error: undefined ident: `d`
+    4 |     arr.sort(a == b)
+    5 |     arr.sort(a > a)
+    6 |     arr.sort(c > d)
+      |                  ^
+    7 | }
diff --git a/vlib/v/checker/tests/array_sort_with_compare_err.out b/vlib/v/checker/tests/array_sort_with_compare_err.out
index 3e8febe9eb..e73ff4f024 100644
--- a/vlib/v/checker/tests/array_sort_with_compare_err.out
+++ b/vlib/v/checker/tests/array_sort_with_compare_err.out
@@ -1,13 +1,20 @@
 vlib/v/checker/tests/array_sort_with_compare_err.vv:11:24: error: sort_with_compare callback function parameter `a` with type `string` should be `&string`
     9 | }
-   10 |
+   10 | 
    11 | fn sort_by_file_base(a string, b string) int {
       |                        ~~~~~~
    12 |     return int(a > b)
    13 | }
+vlib/v/checker/tests/array_sort_with_compare_err.vv:11:34: error: sort_with_compare callback function parameter `b` with type `string` should be `&string`
+    9 | }
+   10 | 
+   11 | fn sort_by_file_base(a string, b string) int {
+      |                                  ~~~~~~
+   12 |     return int(a > b)
+   13 | }
 vlib/v/checker/tests/array_sort_with_compare_err.vv:4:26: error: cannot use `fn (string, string) int` as `fn (voidptr, voidptr) int` in argument 1 to `[]string.sort_with_compare`
     2 |     mut names := ['aaa', 'bbb', 'ccc']
-    3 |
+    3 | 
     4 |     names.sort_with_compare(sort_by_file_base)
       |                             ~~~~~~~~~~~~~~~~~
     5 |     println(names)
@@ -15,7 +22,7 @@ vlib/v/checker/tests/array_sort_with_compare_err.vv:4:26: error: cannot use `fn
 Details: expected argument 1 to be a pointer, but the passed argument 1 is NOT a pointer
 vlib/v/checker/tests/array_sort_with_compare_err.vv:7:26: error: cannot use `int literal` as `fn (voidptr, voidptr) int` in argument 1 to `[]string.sort_with_compare`
     5 |     println(names)
-    6 |
+    6 | 
     7 |     names.sort_with_compare(22)
       |                             ~~
     8 |     println(names)
diff --git a/vlib/v/checker/tests/array_sort_with_compare_ref_elem_err.out b/vlib/v/checker/tests/array_sort_with_compare_ref_elem_err.out
index f7a60a01c0..ce19744dc8 100644
--- a/vlib/v/checker/tests/array_sort_with_compare_ref_elem_err.out
+++ b/vlib/v/checker/tests/array_sort_with_compare_ref_elem_err.out
@@ -1,7 +1,14 @@
 vlib/v/checker/tests/array_sort_with_compare_ref_elem_err.vv:21:23: error: sort_with_compare callback function parameter `a` with type `&Cell` should be `&&Cell`
    19 | }
-   20 |
+   20 | 
    21 | fn sort_cells_by_yx(a &Cell, b &Cell) int {
       |                       ~~~~~
    22 |     if a.pos.y == b.pos.y {
    23 |         if a.pos.x < b.pos.x {
+vlib/v/checker/tests/array_sort_with_compare_ref_elem_err.vv:21:32: error: sort_with_compare callback function parameter `b` with type `&Cell` should be `&&Cell`
+   19 | }
+   20 | 
+   21 | fn sort_cells_by_yx(a &Cell, b &Cell) int {
+      |                                ~~~~~
+   22 |     if a.pos.y == b.pos.y {
+   23 |         if a.pos.x < b.pos.x {
diff --git a/vlib/v/checker/tests/assign_deref_fn_call_on_left_side_err.out b/vlib/v/checker/tests/assign_deref_fn_call_on_left_side_err.out
index d26ab1b0fd..ee93babb34 100644
--- a/vlib/v/checker/tests/assign_deref_fn_call_on_left_side_err.out
+++ b/vlib/v/checker/tests/assign_deref_fn_call_on_left_side_err.out
@@ -1,6 +1,18 @@
 vlib/v/checker/tests/assign_deref_fn_call_on_left_side_err.vv:8:2: error: cannot dereference a function call on the left side of an assignment, use a temporary variable
-    6 |
+    6 | 
     7 | fn main() {
     8 |     *foo('s') = 1
       |     ^
     9 | }
+vlib/v/checker/tests/assign_deref_fn_call_on_left_side_err.vv:8:12: error: modifying variables via dereferencing can only be done in `unsafe` blocks
+    6 | 
+    7 | fn main() {
+    8 |     *foo('s') = 1
+      |               ^
+    9 | }
+vlib/v/checker/tests/assign_deref_fn_call_on_left_side_err.vv:8:14: error: cannot assign to `*foo('s')`: expected `Foo`, not `int literal`
+    6 | 
+    7 | fn main() {
+    8 |     *foo('s') = 1
+      |                 ^
+    9 | }
diff --git a/vlib/v/checker/tests/assign_expr_type_err_b.out b/vlib/v/checker/tests/assign_expr_type_err_b.out
index e5f01cafc9..0cc90bb500 100644
--- a/vlib/v/checker/tests/assign_expr_type_err_b.out
+++ b/vlib/v/checker/tests/assign_expr_type_err_b.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/assign_expr_type_err_b.vv:3:9: error: operator %= not defin
       |            ~~~~~~~
     4 |     _ = foo
     5 | }
+vlib/v/checker/tests/assign_expr_type_err_b.vv:3:9: error: cannot assign to `foo`: expected `int`, not `string`
+    1 | fn main() {
+    2 |     mut foo := 10
+    3 |     foo %= 'hello'
+      |            ~~~~~~~
+    4 |     _ = foo
+    5 | }
diff --git a/vlib/v/checker/tests/assign_expr_type_err_c.out b/vlib/v/checker/tests/assign_expr_type_err_c.out
index 338ce5b87c..8d22c356b1 100644
--- a/vlib/v/checker/tests/assign_expr_type_err_c.out
+++ b/vlib/v/checker/tests/assign_expr_type_err_c.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/assign_expr_type_err_c.vv:3:2: error: operator *= not defin
       |     ~~~
     4 |     _ = foo
     5 | }
+vlib/v/checker/tests/assign_expr_type_err_c.vv:3:9: error: cannot assign to `foo`: expected `string`, not `int literal`
+    1 | fn main() {
+    2 |     mut foo := 'hello'
+    3 |     foo *= 10
+      |            ~~
+    4 |     _ = foo
+    5 | }
diff --git a/vlib/v/checker/tests/assign_expr_type_err_d.out b/vlib/v/checker/tests/assign_expr_type_err_d.out
index 77536290eb..62394fd909 100644
--- a/vlib/v/checker/tests/assign_expr_type_err_d.out
+++ b/vlib/v/checker/tests/assign_expr_type_err_d.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/assign_expr_type_err_d.vv:3:9: error: operator /= not defin
       |            ~~~~
     4 |     _ = foo
     5 | }
+vlib/v/checker/tests/assign_expr_type_err_d.vv:3:9: error: cannot assign to `foo`: expected `f64`, not `bool`
+    1 | fn main() {
+    2 |     mut foo := 1.5
+    3 |     foo /= true
+      |            ~~~~
+    4 |     _ = foo
+    5 | }
diff --git a/vlib/v/checker/tests/assign_expr_type_err_e.out b/vlib/v/checker/tests/assign_expr_type_err_e.out
index b8acd99bc0..ef10ad54d9 100644
--- a/vlib/v/checker/tests/assign_expr_type_err_e.out
+++ b/vlib/v/checker/tests/assign_expr_type_err_e.out
@@ -5,3 +5,17 @@ vlib/v/checker/tests/assign_expr_type_err_e.vv:3:2: error: operator `-=` not def
       |     ~~~
     4 |     _ = foo
     5 | }
+vlib/v/checker/tests/assign_expr_type_err_e.vv:3:9: error: invalid right operand: string -= rune
+    1 | fn main() {
+    2 |     mut foo := 'hello'
+    3 |     foo -= `a`
+      |            ~~~
+    4 |     _ = foo
+    5 | }
+vlib/v/checker/tests/assign_expr_type_err_e.vv:3:9: error: cannot assign to `foo`: expected `string`, not `rune`
+    1 | fn main() {
+    2 |     mut foo := 'hello'
+    3 |     foo -= `a`
+      |            ~~~
+    4 |     _ = foo
+    5 | }
diff --git a/vlib/v/checker/tests/assign_expr_type_err_f.out b/vlib/v/checker/tests/assign_expr_type_err_f.out
index 7cdaa51a41..9775365706 100644
--- a/vlib/v/checker/tests/assign_expr_type_err_f.out
+++ b/vlib/v/checker/tests/assign_expr_type_err_f.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/assign_expr_type_err_f.vv:3:9: error: invalid right operand
       |            ~~~~~
     4 |     _ = foo
     5 | }
+vlib/v/checker/tests/assign_expr_type_err_f.vv:3:9: error: cannot assign to `foo`: expected `int`, not `bool`
+    1 | fn main() {
+    2 |     mut foo := 10
+    3 |     foo -= false
+      |            ~~~~~
+    4 |     _ = foo
+    5 | }
diff --git a/vlib/v/checker/tests/assign_expr_type_err_h.out b/vlib/v/checker/tests/assign_expr_type_err_h.out
index 07d2b6e9d1..55494b2e2c 100644
--- a/vlib/v/checker/tests/assign_expr_type_err_h.out
+++ b/vlib/v/checker/tests/assign_expr_type_err_h.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/assign_expr_type_err_h.vv:3:9: error: invalid right operand
       |            ~~~~~
     4 |     _ = foo
     5 | }
+vlib/v/checker/tests/assign_expr_type_err_h.vv:3:9: error: cannot assign to `foo`: expected `string`, not `bool`
+    1 | fn main() {
+    2 |     mut foo := 'hello'
+    3 |     foo += false
+      |            ~~~~~
+    4 |     _ = foo
+    5 | }
diff --git a/vlib/v/checker/tests/assign_expr_type_err_i.out b/vlib/v/checker/tests/assign_expr_type_err_i.out
index c8450f0fd2..1799f7b2f5 100644
--- a/vlib/v/checker/tests/assign_expr_type_err_i.out
+++ b/vlib/v/checker/tests/assign_expr_type_err_i.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/assign_expr_type_err_i.vv:3:9: error: invalid right operand
       |            ~~~~~~~
     4 |     _ = foo
     5 | }
+vlib/v/checker/tests/assign_expr_type_err_i.vv:3:9: error: cannot assign to `foo`: expected `f64`, not `string`
+    1 | fn main() {
+    2 |     mut foo := 1.5
+    3 |     foo += 'hello'
+      |            ~~~~~~~
+    4 |     _ = foo
+    5 | }
diff --git a/vlib/v/checker/tests/assign_expr_unresolved_variables_err_chain.out b/vlib/v/checker/tests/assign_expr_unresolved_variables_err_chain.out
index 5c7e5cf955..0d82c14886 100644
--- a/vlib/v/checker/tests/assign_expr_unresolved_variables_err_chain.out
+++ b/vlib/v/checker/tests/assign_expr_unresolved_variables_err_chain.out
@@ -4,6 +4,12 @@ vlib/v/checker/tests/assign_expr_unresolved_variables_err_chain.vv:2:7: error: u
       |          ^
     3 |     b := c
     4 |     c := a
+vlib/v/checker/tests/assign_expr_unresolved_variables_err_chain.vv:2:7: error: unresolved variable: `b`
+    1 | fn main() {
+    2 |     a := b
+      |          ^
+    3 |     b := c
+    4 |     c := a
 vlib/v/checker/tests/assign_expr_unresolved_variables_err_chain.vv:3:7: error: undefined variable `c` (used before declaration)
     1 | fn main() {
     2 |     a := b
@@ -11,3 +17,10 @@ vlib/v/checker/tests/assign_expr_unresolved_variables_err_chain.vv:3:7: error: u
       |          ^
     4 |     c := a
     5 |     _ = a
+vlib/v/checker/tests/assign_expr_unresolved_variables_err_chain.vv:3:7: error: unresolved variable: `c`
+    1 | fn main() {
+    2 |     a := b
+    3 |     b := c
+      |          ^
+    4 |     c := a
+    5 |     _ = a
diff --git a/vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.out b/vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.out
index 0c25302819..85e2184a99 100644
--- a/vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.out
+++ b/vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.out
@@ -1,10 +1,3 @@
-vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.vv:11:12: warning: redundant parentheses are used
-    9 | fn foo() {
-   10 |     mut a := &(a_char)
-   11 |     mut b := &((a_char))
-      |               ~~~~~~~~~~
-   12 |     mut c := &((((a_char))))
-   13 |     println(a)
 vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.vv:11:12: warning: redundant parentheses are used
     9 | fn foo() {
    10 |     mut a := &(a_char)
@@ -19,41 +12,6 @@ vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.vv:12:1
       |               ~~~~~~~~~~~~~~
    13 |     println(a)
    14 |     println(b)
-vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.vv:12:13: warning: redundant parentheses are used
-   10 |     mut a := &(a_char)
-   11 |     mut b := &((a_char))
-   12 |     mut c := &((((a_char))))
-      |                ~~~~~~~~~~~~
-   13 |     println(a)
-   14 |     println(b)
-vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.vv:12:14: warning: redundant parentheses are used
-   10 |     mut a := &(a_char)
-   11 |     mut b := &((a_char))
-   12 |     mut c := &((((a_char))))
-      |                 ~~~~~~~~~~
-   13 |     println(a)
-   14 |     println(b)
-vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.vv:12:12: warning: redundant parentheses are used
-   10 |     mut a := &(a_char)
-   11 |     mut b := &((a_char))
-   12 |     mut c := &((((a_char))))
-      |               ~~~~~~~~~~~~~~
-   13 |     println(a)
-   14 |     println(b)
-vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.vv:12:13: warning: redundant parentheses are used
-   10 |     mut a := &(a_char)
-   11 |     mut b := &((a_char))
-   12 |     mut c := &((((a_char))))
-      |                ~~~~~~~~~~~~
-   13 |     println(a)
-   14 |     println(b)
-vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.vv:12:14: warning: redundant parentheses are used
-   10 |     mut a := &(a_char)
-   11 |     mut b := &((a_char))
-   12 |     mut c := &((((a_char))))
-      |                 ~~~~~~~~~~
-   13 |     println(a)
-   14 |     println(b)
 vlib/v/checker/tests/assign_immutable_reference_var_with_parenthesis_err.vv:10:11: error: `a_char` is immutable, cannot have a mutable reference to it
     8 | 
     9 | fn foo() {
diff --git a/vlib/v/checker/tests/assign_multi_immutable_err.out b/vlib/v/checker/tests/assign_multi_immutable_err.out
index 635e02059c..13606c279c 100644
--- a/vlib/v/checker/tests/assign_multi_immutable_err.out
+++ b/vlib/v/checker/tests/assign_multi_immutable_err.out
@@ -3,15 +3,29 @@ vlib/v/checker/tests/assign_multi_immutable_err.vv:4:2: error: `a` is immutable,
     3 |     b := 20
     4 |     a, b = 1, 2
       |     ^
-    5 |
+    5 | 
+    6 |     println('$a, $b')
+vlib/v/checker/tests/assign_multi_immutable_err.vv:4:5: error: `b` is immutable, declare it with `mut` to make it mutable
+    2 |     a := 10
+    3 |     b := 20
+    4 |     a, b = 1, 2
+      |        ^
+    5 | 
     6 |     println('$a, $b')
 vlib/v/checker/tests/assign_multi_immutable_err.vv:18:5: error: cannot assign to function `error`
-   16 |
+   16 | 
    17 | fn assign_fn() {
    18 |     _, error = g()
       |        ~~~~~
    19 |     g = f()
    20 | }
+vlib/v/checker/tests/assign_multi_immutable_err.vv:18:13: error: cannot assign to `error`: expected `fn (string) IError`, not `int`
+   16 | 
+   17 | fn assign_fn() {
+   18 |     _, error = g()
+      |                ~~~
+   19 |     g = f()
+   20 | }
 vlib/v/checker/tests/assign_multi_immutable_err.vv:19:2: error: cannot assign to function `g`
    17 | fn assign_fn() {
    18 |     _, error = g()
@@ -19,3 +33,10 @@ vlib/v/checker/tests/assign_multi_immutable_err.vv:19:2: error: cannot assign to
       |     ^
    20 | }
    21 |
+vlib/v/checker/tests/assign_multi_immutable_err.vv:19:6: error: cannot assign to `g`: expected `fn () (int, int)`, not `int`
+   17 | fn assign_fn() {
+   18 |     _, error = g()
+   19 |     g = f()
+      |         ~~~
+   20 | }
+   21 |
diff --git a/vlib/v/checker/tests/assign_multi_mismatch.out b/vlib/v/checker/tests/assign_multi_mismatch.out
index ded3db72c5..dfea5a2583 100644
--- a/vlib/v/checker/tests/assign_multi_mismatch.out
+++ b/vlib/v/checker/tests/assign_multi_mismatch.out
@@ -33,6 +33,13 @@ vlib/v/checker/tests/assign_multi_mismatch.vv:10:15: error: cannot use multi-val
       |               ~~~
    11 | _, _, _ := f(), 0
    12 | _, _ := f(), f()
+vlib/v/checker/tests/assign_multi_mismatch.vv:10:9: error: assignment mismatch: 3 variable(s) 2 value(s)
+    8 | _, _ := 0, f()
+    9 | _, _ := f(), 0
+   10 | _, _, _ := 0, f()
+      |         ~~
+   11 | _, _, _ := f(), 0
+   12 | _, _ := f(), f()
 vlib/v/checker/tests/assign_multi_mismatch.vv:11:12: error: cannot use multi-value (int, int) in single-value context
     9 | _, _ := f(), 0
    10 | _, _, _ := 0, f()
@@ -40,6 +47,13 @@ vlib/v/checker/tests/assign_multi_mismatch.vv:11:12: error: cannot use multi-val
       |            ~~~
    12 | _, _ := f(), f()
    13 | _, _, _, _ := f(), f()
+vlib/v/checker/tests/assign_multi_mismatch.vv:11:9: error: assignment mismatch: 3 variable(s) but `f()` returns 2 value(s)
+    9 | _, _ := f(), 0
+   10 | _, _, _ := 0, f()
+   11 | _, _, _ := f(), 0
+      |         ~~
+   12 | _, _ := f(), f()
+   13 | _, _, _, _ := f(), f()
 vlib/v/checker/tests/assign_multi_mismatch.vv:12:9: error: cannot use multi-value (int, int) in single-value context
    10 | _, _, _ := 0, f()
    11 | _, _, _ := f(), 0
@@ -54,6 +68,13 @@ vlib/v/checker/tests/assign_multi_mismatch.vv:13:15: error: cannot use multi-val
       |               ~~~
    14 | 
    15 | _, _ := 0, match 4 {
+vlib/v/checker/tests/assign_multi_mismatch.vv:13:12: error: assignment mismatch: 4 variable(s) but `f()` returns 2 value(s)
+   11 | _, _, _ := f(), 0
+   12 | _, _ := f(), f()
+   13 | _, _, _, _ := f(), f()
+      |            ~~
+   14 | 
+   15 | _, _ := 0, match 4 {
 vlib/v/checker/tests/assign_multi_mismatch.vv:19:3: error: assignment mismatch: 1 variable(s) 2 value(s)
    17 |     else { 1 }
    18 | }
diff --git a/vlib/v/checker/tests/assign_to_typeless_variable_err.out b/vlib/v/checker/tests/assign_to_typeless_variable_err.out
index 37ab5d3005..2566b150a9 100644
--- a/vlib/v/checker/tests/assign_to_typeless_variable_err.out
+++ b/vlib/v/checker/tests/assign_to_typeless_variable_err.out
@@ -16,3 +16,9 @@ vlib/v/checker/tests/assign_to_typeless_variable_err.vv:3:3: error: `val` is imm
     3 |   val = 1
       |   ~~~
     4 | }
+vlib/v/checker/tests/assign_to_typeless_variable_err.vv:3:9: error: cannot assign to `val`: expected `void`, not `int literal`
+    1 | fn main() {
+    2 |   val := {}
+    3 |   val = 1
+      |         ^
+    4 | }
diff --git a/vlib/v/checker/tests/blank_ident_invalid_use.out b/vlib/v/checker/tests/blank_ident_invalid_use.out
index 9385664f59..3f719b58e5 100644
--- a/vlib/v/checker/tests/blank_ident_invalid_use.out
+++ b/vlib/v/checker/tests/blank_ident_invalid_use.out
@@ -3,3 +3,8 @@ vlib/v/checker/tests/blank_ident_invalid_use.vv:2:8: error: undefined ident: `_`
     2 |     _ := [_]
       |           ^
     3 | }
+vlib/v/checker/tests/blank_ident_invalid_use.vv:2:8: error: invalid void array element type
+    1 | fn main() {
+    2 |     _ := [_]
+      |           ^
+    3 | }
diff --git a/vlib/v/checker/tests/cannot_cast_to_struct.out b/vlib/v/checker/tests/cannot_cast_to_struct.out
index 8445bb1b1e..889a1625ed 100644
--- a/vlib/v/checker/tests/cannot_cast_to_struct.out
+++ b/vlib/v/checker/tests/cannot_cast_to_struct.out
@@ -19,6 +19,13 @@ vlib/v/checker/tests/cannot_cast_to_struct.vv:12:6: error: cannot cast `Alphabet
       |         ~~~~~~~~
    13 |     _ = Xyz(5)
    14 |     s := Abc{}
+vlib/v/checker/tests/cannot_cast_to_struct.vv:12:6: error: cannot cast `Alphabet` sum type value to `Xyz`, use `sum as Xyz` instead
+   10 |     _ := Test(Abc{})
+   11 |     sum := Alphabet(Xyz{})
+   12 |     _ = Xyz(sum)
+      |         ~~~~~~~~
+   13 |     _ = Xyz(5)
+   14 |     s := Abc{}
 vlib/v/checker/tests/cannot_cast_to_struct.vv:13:6: error: cannot cast `int literal` to struct
    11 |     sum := Alphabet(Xyz{})
    12 |     _ = Xyz(sum)
diff --git a/vlib/v/checker/tests/cast_string_err.out b/vlib/v/checker/tests/cast_string_err.out
index 86625cf033..f33fc50c05 100644
--- a/vlib/v/checker/tests/cast_string_err.out
+++ b/vlib/v/checker/tests/cast_string_err.out
@@ -12,6 +12,13 @@ vlib/v/checker/tests/cast_string_err.vv:18:9: error: cannot cast sumtype `Sumtyp
       |            ~~~~~~~~~~
    19 |     println(sst)
    20 |     //
+vlib/v/checker/tests/cast_string_err.vv:18:9: error: cannot cast `Sumtype` sum type value to `string`, use `st as string` instead
+   16 |     //
+   17 |     st := Sumtype(int(456))
+   18 |     sst := string(st)
+      |            ~~~~~~~~~~
+   19 |     println(sst)
+   20 |     //
 vlib/v/checker/tests/cast_string_err.vv:22:10: error: cannot cast struct `Abc` to `string`
    20 |     //
    21 |     abc := Abc{}
diff --git a/vlib/v/checker/tests/chan_mut.out b/vlib/v/checker/tests/chan_mut.out
index e82419b97d..b2b6c96a9b 100644
--- a/vlib/v/checker/tests/chan_mut.out
+++ b/vlib/v/checker/tests/chan_mut.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/chan_mut.vv:8:8: error: `v` is immutable, declare it with `
       |           ^
     9 |     mut w := St{}
    10 |     ch <- w
+vlib/v/checker/tests/chan_mut.vv:8:8: error: cannot push non-reference `St` on `chan mut St`
+    6 | fn f(ch chan mut St) {
+    7 |     v := St{}
+    8 |     ch <- v
+      |           ^
+    9 |     mut w := St{}
+   10 |     ch <- w
 vlib/v/checker/tests/chan_mut.vv:10:8: error: cannot push non-reference `St` on `chan mut St`
     8 |     ch <- v
     9 |     mut w := St{}
diff --git a/vlib/v/checker/tests/comptime_call_no_unused_var.out b/vlib/v/checker/tests/comptime_call_no_unused_var.out
index 17aae7c95a..0aecbc4ca1 100644
--- a/vlib/v/checker/tests/comptime_call_no_unused_var.out
+++ b/vlib/v/checker/tests/comptime_call_no_unused_var.out
@@ -19,6 +19,13 @@ vlib/v/checker/tests/comptime_call_no_unused_var.vv:15:8: error: todo: not a str
       |           ^
    16 |     s2 := 'x'
    17 |     test.$s2()
+vlib/v/checker/tests/comptime_call_no_unused_var.vv:15:8: error: could not find method ``
+   13 |     test.$v()
+   14 |     s := 'x' + 'y'
+   15 |     test.$s()
+      |           ^
+   16 |     s2 := 'x'
+   17 |     test.$s2()
 vlib/v/checker/tests/comptime_call_no_unused_var.vv:17:8: error: could not find method `x`
    15 |     test.$s()
    16 |     s2 := 'x'
diff --git a/vlib/v/checker/tests/comptime_field_selector_not_in_for_err.out b/vlib/v/checker/tests/comptime_field_selector_not_in_for_err.out
index bc3e1f95f8..6b7a2bb723 100644
--- a/vlib/v/checker/tests/comptime_field_selector_not_in_for_err.out
+++ b/vlib/v/checker/tests/comptime_field_selector_not_in_for_err.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/comptime_field_selector_not_in_for_err.vv:9:6: error: expec
       |         ~~~~
    10 | }
    11 |
+vlib/v/checker/tests/comptime_field_selector_not_in_for_err.vv:9:14: error: cannot assign to `t.$(name)`: expected `void`, not `string`
+    7 |     mut t := T{}
+    8 |     name := 'test'
+    9 |     t.$(name) = '3'
+      |                 ~~~
+   10 | }
+   11 |
diff --git a/vlib/v/checker/tests/comptime_field_selector_not_name_err.out b/vlib/v/checker/tests/comptime_field_selector_not_name_err.out
index c53955c555..4461226740 100644
--- a/vlib/v/checker/tests/comptime_field_selector_not_name_err.out
+++ b/vlib/v/checker/tests/comptime_field_selector_not_name_err.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/comptime_field_selector_not_name_err.vv:10:8: error: expect
       |                 ^
    11 |             fv := Foo{}
    12 |             _ = t.$(fv.name)
+vlib/v/checker/tests/comptime_field_selector_not_name_err.vv:10:8: error: expected selector expression e.g. `$(field.name)`
+    8 |     $for f in T.fields {
+    9 |         $if f.typ is string {
+   10 |             t.$(f) = '3'
+      |                 ^
+   11 |             fv := Foo{}
+   12 |             _ = t.$(fv.name)
 vlib/v/checker/tests/comptime_field_selector_not_name_err.vv:12:12: error: unknown `$for` variable `fv`
    10 |             t.$(f) = '3'
    11 |             fv := Foo{}
@@ -19,3 +26,17 @@ vlib/v/checker/tests/comptime_field_selector_not_name_err.vv:15:10: error: undef
       |             ^
    16 | }
    17 |
+vlib/v/checker/tests/comptime_field_selector_not_name_err.vv:15:12: error: `f` does not return a value
+   13 |         }
+   14 |     }
+   15 |     _ = t.$(f.name)
+      |               ~~~~
+   16 | }
+   17 |
+vlib/v/checker/tests/comptime_field_selector_not_name_err.vv:15:12: error: expected `string` instead of `void` (e.g. `field.name`)
+   13 |         }
+   14 |     }
+   15 |     _ = t.$(f.name)
+      |               ~~~~
+   16 | }
+   17 |
diff --git a/vlib/v/checker/tests/const_cycle_decl_err.out b/vlib/v/checker/tests/const_cycle_decl_err.out
index 9cb350cc54..1bdc829219 100644
--- a/vlib/v/checker/tests/const_cycle_decl_err.out
+++ b/vlib/v/checker/tests/const_cycle_decl_err.out
@@ -1,3 +1,6 @@
 vlib/v/checker/tests/const_cycle_decl_err.vv:1:11: error: cycle in constant `a`
     1 | const a = a + 0
       |           ^
+vlib/v/checker/tests/const_cycle_decl_err.vv:1:11: error: mismatched types `void` and `int literal`
+    1 | const a = a + 0
+      |           ~~~~~
diff --git a/vlib/v/checker/tests/const_expr_match_range_invalid_err.out b/vlib/v/checker/tests/const_expr_match_range_invalid_err.out
index 21d35d878d..89e1b23766 100644
--- a/vlib/v/checker/tests/const_expr_match_range_invalid_err.out
+++ b/vlib/v/checker/tests/const_expr_match_range_invalid_err.out
@@ -18,3 +18,20 @@ vlib/v/checker/tests/const_expr_match_range_invalid_err.vv:9:2: error: the low a
 Details: 
  low part type: string
 high part type: int literal
+vlib/v/checker/tests/const_expr_match_range_invalid_err.vv:9:2: error: the range type and the match condition type should match
+    7 |         println(start)
+    8 |     }
+    9 |     'str'...end {
+      |     ~~~~~~~~~~~
+   10 |         println(end)
+   11 |     }
+Details: 
+match condition type: int
+          range type: string
+vlib/v/checker/tests/const_expr_match_range_invalid_err.vv:9:2: error: match branch range expressions need the start value to be known at compile time (only enums, const or literals are supported)
+    7 |         println(start)
+    8 |     }
+    9 |     'str'...end {
+      |     ~~~~~
+   10 |         println(end)
+   11 |     }
diff --git a/vlib/v/checker/tests/const_match_invalid_type_range_err.out b/vlib/v/checker/tests/const_match_invalid_type_range_err.out
index 792fbcdd36..dc4eb5c53a 100644
--- a/vlib/v/checker/tests/const_match_invalid_type_range_err.out
+++ b/vlib/v/checker/tests/const_match_invalid_type_range_err.out
@@ -8,6 +8,13 @@ vlib/v/checker/tests/const_match_invalid_type_range_err.vv:6:2: error: the range
 Details: 
 match condition type: int
           range type: rune
+vlib/v/checker/tests/const_match_invalid_type_range_err.vv:6:2: error: the start value `97` should be lower than the end value `2`
+    4 | 
+    5 | match 5 {
+    6 |     start...end {
+      |     ~~~~~~~~~~~
+    7 |         println(start)
+    8 |     }
 vlib/v/checker/tests/const_match_invalid_type_range_err.vv:13:2: error: the range type and the match condition type should match
    11 | 
    12 | b := match 5 {
@@ -18,3 +25,10 @@ vlib/v/checker/tests/const_match_invalid_type_range_err.vv:13:2: error: the rang
 Details: 
 match condition type: int
           range type: rune
+vlib/v/checker/tests/const_match_invalid_type_range_err.vv:13:2: error: the start value `97` should be lower than the end value `2`
+   11 | 
+   12 | b := match 5 {
+   13 |     start...end {
+      |     ~~~~~~~~~~~
+   14 |         3
+   15 |     }
diff --git a/vlib/v/checker/tests/const_match_mismatch_end_range_err.out b/vlib/v/checker/tests/const_match_mismatch_end_range_err.out
index b654b77ffb..c21b1d1570 100644
--- a/vlib/v/checker/tests/const_match_mismatch_end_range_err.out
+++ b/vlib/v/checker/tests/const_match_mismatch_end_range_err.out
@@ -18,6 +18,13 @@ vlib/v/checker/tests/const_match_mismatch_end_range_err.vv:9:2: error: the range
 Details: 
 match condition type: int
           range type: rune
+vlib/v/checker/tests/const_match_mismatch_end_range_err.vv:9:2: error: the start value `97` should be lower than the end value `12`
+    7 |         println(start)
+    8 |     }
+    9 |     `a`...start {
+      |     ~~~~~~~~~~~
+   10 |         println(end)
+   11 |     }
 vlib/v/checker/tests/const_match_mismatch_end_range_err.vv:16:2: error: the range type and the match condition type should match
    14 | 
    15 | a := match 5 {
@@ -38,3 +45,10 @@ vlib/v/checker/tests/const_match_mismatch_end_range_err.vv:19:2: error: the rang
 Details: 
 match condition type: int
           range type: rune
+vlib/v/checker/tests/const_match_mismatch_end_range_err.vv:19:2: error: the start value `97` should be lower than the end value `12`
+   17 |         1
+   18 |     }
+   19 |     `a`...start {
+      |     ~~~~~~~~~~~
+   20 |         `a`
+   21 |     }
diff --git a/vlib/v/checker/tests/const_match_range_duplicate_case_err.out b/vlib/v/checker/tests/const_match_range_duplicate_case_err.out
index b23875977d..9b4f76aa7d 100644
--- a/vlib/v/checker/tests/const_match_range_duplicate_case_err.out
+++ b/vlib/v/checker/tests/const_match_range_duplicate_case_err.out
@@ -5,6 +5,76 @@ vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:9:2: error: match c
       |     ~~~~~~~~~~~
    10 |         println(3)
    11 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:9:2: error: match case `3` is handled more than once
+    7 |         println(1)
+    8 |     }
+    9 |     start...end {
+      |     ~~~~~~~~~~~
+   10 |         println(3)
+   11 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:9:2: error: match case `4` is handled more than once
+    7 |         println(1)
+    8 |     }
+    9 |     start...end {
+      |     ~~~~~~~~~~~
+   10 |         println(3)
+   11 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:9:2: error: match case `5` is handled more than once
+    7 |         println(1)
+    8 |     }
+    9 |     start...end {
+      |     ~~~~~~~~~~~
+   10 |         println(3)
+   11 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:9:2: error: match case `6` is handled more than once
+    7 |         println(1)
+    8 |     }
+    9 |     start...end {
+      |     ~~~~~~~~~~~
+   10 |         println(3)
+   11 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:9:2: error: match case `7` is handled more than once
+    7 |         println(1)
+    8 |     }
+    9 |     start...end {
+      |     ~~~~~~~~~~~
+   10 |         println(3)
+   11 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:9:2: error: match case `8` is handled more than once
+    7 |         println(1)
+    8 |     }
+    9 |     start...end {
+      |     ~~~~~~~~~~~
+   10 |         println(3)
+   11 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:9:2: error: match case `9` is handled more than once
+    7 |         println(1)
+    8 |     }
+    9 |     start...end {
+      |     ~~~~~~~~~~~
+   10 |         println(3)
+   11 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:9:2: error: match case `10` is handled more than once
+    7 |         println(1)
+    8 |     }
+    9 |     start...end {
+      |     ~~~~~~~~~~~
+   10 |         println(3)
+   11 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:9:2: error: match case `11` is handled more than once
+    7 |         println(1)
+    8 |     }
+    9 |     start...end {
+      |     ~~~~~~~~~~~
+   10 |         println(3)
+   11 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:9:2: error: match case `12` is handled more than once
+    7 |         println(1)
+    8 |     }
+    9 |     start...end {
+      |     ~~~~~~~~~~~
+   10 |         println(3)
+   11 |     }
 vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match case `2` is handled more than once
    19 |         1
    20 |     }
@@ -12,3 +82,73 @@ vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match
       |     ~~~~~~~~~~~
    22 |         3
    23 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match case `3` is handled more than once
+   19 |         1
+   20 |     }
+   21 |     start...end {
+      |     ~~~~~~~~~~~
+   22 |         3
+   23 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match case `4` is handled more than once
+   19 |         1
+   20 |     }
+   21 |     start...end {
+      |     ~~~~~~~~~~~
+   22 |         3
+   23 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match case `5` is handled more than once
+   19 |         1
+   20 |     }
+   21 |     start...end {
+      |     ~~~~~~~~~~~
+   22 |         3
+   23 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match case `6` is handled more than once
+   19 |         1
+   20 |     }
+   21 |     start...end {
+      |     ~~~~~~~~~~~
+   22 |         3
+   23 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match case `7` is handled more than once
+   19 |         1
+   20 |     }
+   21 |     start...end {
+      |     ~~~~~~~~~~~
+   22 |         3
+   23 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match case `8` is handled more than once
+   19 |         1
+   20 |     }
+   21 |     start...end {
+      |     ~~~~~~~~~~~
+   22 |         3
+   23 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match case `9` is handled more than once
+   19 |         1
+   20 |     }
+   21 |     start...end {
+      |     ~~~~~~~~~~~
+   22 |         3
+   23 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match case `10` is handled more than once
+   19 |         1
+   20 |     }
+   21 |     start...end {
+      |     ~~~~~~~~~~~
+   22 |         3
+   23 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match case `11` is handled more than once
+   19 |         1
+   20 |     }
+   21 |     start...end {
+      |     ~~~~~~~~~~~
+   22 |         3
+   23 |     }
+vlib/v/checker/tests/const_match_range_duplicate_case_err.vv:21:2: error: match case `12` is handled more than once
+   19 |         1
+   20 |     }
+   21 |     start...end {
+      |     ~~~~~~~~~~~
+   22 |         3
+   23 |     }
diff --git a/vlib/v/checker/tests/const_match_type_mismatch_range_err.out b/vlib/v/checker/tests/const_match_type_mismatch_range_err.out
index 768c2a4124..9df1cea105 100644
--- a/vlib/v/checker/tests/const_match_type_mismatch_range_err.out
+++ b/vlib/v/checker/tests/const_match_type_mismatch_range_err.out
@@ -8,6 +8,23 @@ vlib/v/checker/tests/const_match_type_mismatch_range_err.vv:6:2: error: the low
 Details: 
  low part type: string
 high part type: int literal
+vlib/v/checker/tests/const_match_type_mismatch_range_err.vv:6:2: error: the range type and the match condition type should match
+    4 | 
+    5 | match 5 {
+    6 |     start...end {
+      |     ~~~~~~~~~~~
+    7 |         println(start)
+    8 |     }
+Details: 
+match condition type: int
+          range type: string
+vlib/v/checker/tests/const_match_type_mismatch_range_err.vv:6:2: error: match branch range expressions need the start value to be known at compile time (only enums, const or literals are supported)
+    4 | 
+    5 | match 5 {
+    6 |     start...end {
+      |     ~~~~~
+    7 |         println(start)
+    8 |     }
 vlib/v/checker/tests/const_match_type_mismatch_range_err.vv:13:2: error: the low and high parts of a range expression, should have matching types
    11 | 
    12 | z := match 5 {
@@ -18,3 +35,20 @@ vlib/v/checker/tests/const_match_type_mismatch_range_err.vv:13:2: error: the low
 Details: 
  low part type: string
 high part type: int literal
+vlib/v/checker/tests/const_match_type_mismatch_range_err.vv:13:2: error: the range type and the match condition type should match
+   11 | 
+   12 | z := match 5 {
+   13 |     start...end {
+      |     ~~~~~~~~~~~
+   14 |         2
+   15 |     }
+Details: 
+match condition type: int
+          range type: string
+vlib/v/checker/tests/const_match_type_mismatch_range_err.vv:13:2: error: match branch range expressions need the start value to be known at compile time (only enums, const or literals are supported)
+   11 | 
+   12 | z := match 5 {
+   13 |     start...end {
+      |     ~~~~~
+   14 |         2
+   15 |     }
diff --git a/vlib/v/checker/tests/custom_comptime_define_error.out b/vlib/v/checker/tests/custom_comptime_define_error.out
index 6d48ace842..a0db877460 100644
--- a/vlib/v/checker/tests/custom_comptime_define_error.out
+++ b/vlib/v/checker/tests/custom_comptime_define_error.out
@@ -4,4 +4,11 @@ vlib/v/checker/tests/custom_comptime_define_error.vv:6:6: error: undefined ident
     6 |     $if mysymbol {
       |         ~~~~~~~~
     7 |         // this will produce a checker error when `-d mysymbol` is not given on the CLI
-    8 |         println('comptime non-option define works')
\ No newline at end of file
+    8 |         println('comptime non-option define works')
+vlib/v/checker/tests/custom_comptime_define_error.vv:6:2: error: unknown var: `mysymbol`
+    4 |         println('comptime option define works')
+    5 |     }
+    6 |     $if mysymbol {
+      |     ~~~~~~~~~~~~
+    7 |         // this will produce a checker error when `-d mysymbol` is not given on the CLI
+    8 |         println('comptime non-option define works')
diff --git a/vlib/v/checker/tests/decompose_type_err.out b/vlib/v/checker/tests/decompose_type_err.out
index 95d56f66c0..4cf8931dc6 100644
--- a/vlib/v/checker/tests/decompose_type_err.out
+++ b/vlib/v/checker/tests/decompose_type_err.out
@@ -1,6 +1,12 @@
 vlib/v/checker/tests/decompose_type_err.vv:4:13: error: decomposition can only be used on arrays
-    2 |
+    2 | 
     3 | fn main() {
     4 |     varargs(...123)
       |                ~~~
-    5 | }
\ No newline at end of file
+    5 | }
+vlib/v/checker/tests/decompose_type_err.vv:4:10: error: `ast.ArrayDecompose` (no value) used as value in argument 1 to `varargs`
+    2 | 
+    3 | fn main() {
+    4 |     varargs(...123)
+      |             ~~~~~~
+    5 | }
diff --git a/vlib/v/checker/tests/defer_use_multi_return_value_with_index_out_of_bounds.out b/vlib/v/checker/tests/defer_use_multi_return_value_with_index_out_of_bounds.out
index 08cdc16849..7355d6f59c 100644
--- a/vlib/v/checker/tests/defer_use_multi_return_value_with_index_out_of_bounds.out
+++ b/vlib/v/checker/tests/defer_use_multi_return_value_with_index_out_of_bounds.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/defer_use_multi_return_value_with_index_out_of_bounds.vv:3:
       |                 ~~~~~~~
     4 |     }
     5 |     return 'test', 'test2'
+vlib/v/checker/tests/defer_use_multi_return_value_with_index_out_of_bounds.vv:3:3: error: `println` can not print void expressions
+    1 | fn test() (string, string) {
+    2 |     defer {
+    3 |         println($res(2))
+      |         ~~~~~~~~~~~~~~~~
+    4 |     }
+    5 |     return 'test', 'test2'
diff --git a/vlib/v/checker/tests/defer_use_multi_return_value_without_index.out b/vlib/v/checker/tests/defer_use_multi_return_value_without_index.out
index 70898e96c4..369cadbd64 100644
--- a/vlib/v/checker/tests/defer_use_multi_return_value_without_index.out
+++ b/vlib/v/checker/tests/defer_use_multi_return_value_without_index.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/defer_use_multi_return_value_without_index.vv:3:11: error:
       |                 ~~~~~~
     4 |     }
     5 |     return 'test', 'test2'
+vlib/v/checker/tests/defer_use_multi_return_value_without_index.vv:3:3: error: `println` can not print void expressions
+    1 | fn test() (string, string) {
+    2 |     defer {
+    3 |         println($res())
+      |         ~~~~~~~~~~~~~~~
+    4 |     }
+    5 |     return 'test', 'test2'
diff --git a/vlib/v/checker/tests/defer_use_returned_value_when_nothing_is_returned.out b/vlib/v/checker/tests/defer_use_returned_value_when_nothing_is_returned.out
index 88094686f5..6c13487981 100644
--- a/vlib/v/checker/tests/defer_use_returned_value_when_nothing_is_returned.out
+++ b/vlib/v/checker/tests/defer_use_returned_value_when_nothing_is_returned.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/defer_use_returned_value_when_nothing_is_returned.vv:3:11:
       |                 ~~~~~~
     4 |     }
     5 | }
+vlib/v/checker/tests/defer_use_returned_value_when_nothing_is_returned.vv:3:3: error: `println` can not print void expressions
+    1 | fn test() {
+    2 |     defer {
+    3 |         println($res())
+      |         ~~~~~~~~~~~~~~~
+    4 |     }
+    5 | }
diff --git a/vlib/v/checker/tests/defer_use_returned_value_when_result_is_returned.out b/vlib/v/checker/tests/defer_use_returned_value_when_result_is_returned.out
index ca8995cdc5..fccaf01f45 100644
--- a/vlib/v/checker/tests/defer_use_returned_value_when_result_is_returned.out
+++ b/vlib/v/checker/tests/defer_use_returned_value_when_result_is_returned.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/defer_use_returned_value_when_result_is_returned.vv:3:11: e
       |                 ~~~~~~
     4 |     }
     5 |     return 'test'
+vlib/v/checker/tests/defer_use_returned_value_when_result_is_returned.vv:3:3: error: `println` can not print void expressions
+    1 | fn test() !string {
+    2 |     defer {
+    3 |         println($res())
+      |         ~~~~~~~~~~~~~~~
+    4 |     }
+    5 |     return 'test'
diff --git a/vlib/v/checker/tests/div_op_wrong_type_err.out b/vlib/v/checker/tests/div_op_wrong_type_err.out
index f79c286a71..aecfce2d18 100644
--- a/vlib/v/checker/tests/div_op_wrong_type_err.out
+++ b/vlib/v/checker/tests/div_op_wrong_type_err.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/div_op_wrong_type_err.vv:3:13: error: mismatched types `Aaa
       |             ~~~~~~~~~~
     4 |     println(10 / Aaa{})
     5 |     println([1,2,3] / 10)
+vlib/v/checker/tests/div_op_wrong_type_err.vv:3:13: error: infix expr: cannot use `int literal` (right expression) as `Aaa`
+    1 | struct Aaa{}
+    2 | fn main() {
+    3 |     println(Aaa{} / 10)
+      |             ~~~~~~~~~~
+    4 |     println(10 / Aaa{})
+    5 |     println([1,2,3] / 10)
 vlib/v/checker/tests/div_op_wrong_type_err.vv:4:13: error: mismatched types `int literal` and `Aaa`
     2 | fn main() {
     3 |     println(Aaa{} / 10)
@@ -12,6 +19,13 @@ vlib/v/checker/tests/div_op_wrong_type_err.vv:4:13: error: mismatched types `int
       |             ~~~~~~~~~~
     5 |     println([1,2,3] / 10)
     6 |     println(10 / [1,2,3])
+vlib/v/checker/tests/div_op_wrong_type_err.vv:4:13: error: infix expr: cannot use `Aaa` (right expression) as `int literal`
+    2 | fn main() {
+    3 |     println(Aaa{} / 10)
+    4 |     println(10 / Aaa{})
+      |             ~~~~~~~~~~
+    5 |     println([1,2,3] / 10)
+    6 |     println(10 / [1,2,3])
 vlib/v/checker/tests/div_op_wrong_type_err.vv:5:13: error: mismatched types `[]int` and `int literal`
     3 |     println(Aaa{} / 10)
     4 |     println(10 / Aaa{})
@@ -19,6 +33,13 @@ vlib/v/checker/tests/div_op_wrong_type_err.vv:5:13: error: mismatched types `[]i
       |             ~~~~~~~~~~~~
     6 |     println(10 / [1,2,3])
     7 |     a := map[string]int
+vlib/v/checker/tests/div_op_wrong_type_err.vv:5:13: error: infix expr: cannot use `int literal` (right expression) as `[]int`
+    3 |     println(Aaa{} / 10)
+    4 |     println(10 / Aaa{})
+    5 |     println([1,2,3] / 10)
+      |             ~~~~~~~~~~~~
+    6 |     println(10 / [1,2,3])
+    7 |     a := map[string]int
 vlib/v/checker/tests/div_op_wrong_type_err.vv:6:13: error: mismatched types `int literal` and `[]int`
     4 |     println(10 / Aaa{})
     5 |     println([1,2,3] / 10)
@@ -26,6 +47,13 @@ vlib/v/checker/tests/div_op_wrong_type_err.vv:6:13: error: mismatched types `int
       |             ~~~~~~~~~~~~
     7 |     a := map[string]int
     8 |     println(a / 10)
+vlib/v/checker/tests/div_op_wrong_type_err.vv:6:13: error: infix expr: cannot use `[]int` (right expression) as `int literal`
+    4 |     println(10 / Aaa{})
+    5 |     println([1,2,3] / 10)
+    6 |     println(10 / [1,2,3])
+      |             ~~~~~~~~~~~~
+    7 |     a := map[string]int
+    8 |     println(a / 10)
 vlib/v/checker/tests/div_op_wrong_type_err.vv:8:13: error: mismatched types `map[string]int` and `int literal`
     6 |     println(10 / [1,2,3])
     7 |     a := map[string]int
@@ -33,10 +61,22 @@ vlib/v/checker/tests/div_op_wrong_type_err.vv:8:13: error: mismatched types `map
       |             ~~~~~~
     9 |     println(10 / a)
    10 | }
+vlib/v/checker/tests/div_op_wrong_type_err.vv:8:13: error: infix expr: cannot use `int literal` (right expression) as `map[string]int`
+    6 |     println(10 / [1,2,3])
+    7 |     a := map[string]int
+    8 |     println(a / 10)
+      |             ~~~~~~
+    9 |     println(10 / a)
+   10 | }
 vlib/v/checker/tests/div_op_wrong_type_err.vv:9:13: error: mismatched types `int literal` and `map[string]int`
     7 |     a := map[string]int
     8 |     println(a / 10)
     9 |     println(10 / a)
       |             ~~~~~~
    10 | }
-
+vlib/v/checker/tests/div_op_wrong_type_err.vv:9:13: error: infix expr: cannot use `map[string]int` (right expression) as `int literal`
+    7 |     a := map[string]int
+    8 |     println(a / 10)
+    9 |     println(10 / a)
+      |             ~~~~~~
+   10 | }
diff --git a/vlib/v/checker/tests/enum_op_err.out b/vlib/v/checker/tests/enum_op_err.out
index 1392251852..4d69b14c4e 100644
--- a/vlib/v/checker/tests/enum_op_err.out
+++ b/vlib/v/checker/tests/enum_op_err.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/enum_op_err.vv:8:20: error: only `==` and `!=` are defined on `enum`, use an explicit cast to `int` if needed
-    6 |
+    6 | 
     7 | fn main() {
     8 |     println(Color.red > Color.green)
       |                       ^
@@ -19,6 +19,20 @@ vlib/v/checker/tests/enum_op_err.vv:10:10: error: left operand for `&&` is not a
       |             ~~~~~~~~~
    11 |     println(Color.red | Color.green)
    12 |     println(Color.red & Color.green)
+vlib/v/checker/tests/enum_op_err.vv:10:23: error: right operand for `&&` is not a boolean
+    8 |     println(Color.red > Color.green)
+    9 |     println(Color.red + Color.green)
+   10 |     println(Color.red && Color.green)
+      |                          ~~~~~~~~~~~
+   11 |     println(Color.red | Color.green)
+   12 |     println(Color.red & Color.green)
+vlib/v/checker/tests/enum_op_err.vv:10:20: error: only `==` and `!=` are defined on `enum`, use an explicit cast to `int` if needed
+    8 |     println(Color.red > Color.green)
+    9 |     println(Color.red + Color.green)
+   10 |     println(Color.red && Color.green)
+      |                       ~~
+   11 |     println(Color.red | Color.green)
+   12 |     println(Color.red & Color.green)
 vlib/v/checker/tests/enum_op_err.vv:11:20: error: only `==` and `!=` are defined on `enum`, use an explicit cast to `int` if needed
     9 |     println(Color.red + Color.green)
    10 |     println(Color.red && Color.green)
diff --git a/vlib/v/checker/tests/enum_op_flag_err.out b/vlib/v/checker/tests/enum_op_flag_err.out
index fb3e228e0a..cf9ce5117a 100644
--- a/vlib/v/checker/tests/enum_op_flag_err.out
+++ b/vlib/v/checker/tests/enum_op_flag_err.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/enum_op_flag_err.vv:9:24: error: only `==`, `!=`, `|` and `&` are defined on `[flag]` tagged `enum`, use an explicit cast to `int` if needed
-    7 |
+    7 | 
     8 | fn main() {
     9 |     println(FilePerm.read > FilePerm.write)
       |                           ^
@@ -18,3 +18,15 @@ vlib/v/checker/tests/enum_op_flag_err.vv:11:10: error: left operand for `&&` is
    11 |     println(FilePerm.write && FilePerm.exec)
       |             ~~~~~~~~~~~~~~
    12 | }
+vlib/v/checker/tests/enum_op_flag_err.vv:11:28: error: right operand for `&&` is not a boolean
+    9 |     println(FilePerm.read > FilePerm.write)
+   10 |     println(FilePerm.write + FilePerm.exec)
+   11 |     println(FilePerm.write && FilePerm.exec)
+      |                               ~~~~~~~~~~~~~
+   12 | }
+vlib/v/checker/tests/enum_op_flag_err.vv:11:25: error: only `==`, `!=`, `|` and `&` are defined on `[flag]` tagged `enum`, use an explicit cast to `int` if needed
+    9 |     println(FilePerm.read > FilePerm.write)
+   10 |     println(FilePerm.write + FilePerm.exec)
+   11 |     println(FilePerm.write && FilePerm.exec)
+      |                            ~~
+   12 | }
diff --git a/vlib/v/checker/tests/error_with_several_comments_with_crlf_ending.out b/vlib/v/checker/tests/error_with_several_comments_with_crlf_ending.out
index d1b88fa9b7..caab66c255 100644
--- a/vlib/v/checker/tests/error_with_several_comments_with_crlf_ending.out
+++ b/vlib/v/checker/tests/error_with_several_comments_with_crlf_ending.out
@@ -5,9 +5,22 @@ vlib/v/checker/tests/error_with_several_comments_with_crlf_ending.vv:9:2: error:
       |     ^
    10 |     println('a is $a')
    11 | }
+vlib/v/checker/tests/error_with_several_comments_with_crlf_ending.vv:9:6: error: cannot assign to `a`: expected `void`, not `int literal`
+    7 | fn main() {
+    8 |     func1()
+    9 |     a = 2
+      |         ^
+   10 |     println('a is $a')
+   11 | }
 vlib/v/checker/tests/error_with_several_comments_with_crlf_ending.vv:10:17: error: undefined ident: `a`
     8 |     func1()
     9 |     a = 2
    10 |     println('a is $a')
       |                    ^
    11 | }
+vlib/v/checker/tests/error_with_several_comments_with_crlf_ending.vv:10:17: error: expression does not return a value
+    8 |     func1()
+    9 |     a = 2
+   10 |     println('a is $a')
+      |                    ^
+   11 | }
diff --git a/vlib/v/checker/tests/filter_on_non_arr_err.out b/vlib/v/checker/tests/filter_on_non_arr_err.out
index d01f0fd2e4..b3b298da31 100644
--- a/vlib/v/checker/tests/filter_on_non_arr_err.out
+++ b/vlib/v/checker/tests/filter_on_non_arr_err.out
@@ -3,3 +3,8 @@ vlib/v/checker/tests/filter_on_non_arr_err.vv:2:14: error: unknown method or fie
     2 |     _ := 'test'.filter(it == `t`)
       |                 ~~~~~~~~~~~~~~~~~
     3 | }
+vlib/v/checker/tests/filter_on_non_arr_err.vv:2:4: error: assignment mismatch: 1 variable(s) but `filter()` returns 0 value(s)
+    1 | fn main() {
+    2 |     _ := 'test'.filter(it == `t`)
+      |       ~~
+    3 | }
diff --git a/vlib/v/checker/tests/fixed_array_conv.out b/vlib/v/checker/tests/fixed_array_conv.out
index 79f961ff7c..bf6a171fe0 100644
--- a/vlib/v/checker/tests/fixed_array_conv.out
+++ b/vlib/v/checker/tests/fixed_array_conv.out
@@ -12,6 +12,13 @@ vlib/v/checker/tests/fixed_array_conv.vv:3:3: error: mismatched types `voidptr`
       |   ^
     4 | mut ip := &int(0)
     5 | ip = arr
+vlib/v/checker/tests/fixed_array_conv.vv:3:5: error: cannot assign to `p`: expected `voidptr`, not `[2]int`
+    1 | arr := [2, 3]!
+    2 | mut p := unsafe { nil }
+    3 | p = arr
+      |     ~~~
+    4 | mut ip := &int(0)
+    5 | ip = arr
 vlib/v/checker/tests/fixed_array_conv.vv:5:4: error: mismatched types `&int` and `[2]int`
     3 | p = arr
     4 | mut ip := &int(0)
@@ -19,6 +26,13 @@ vlib/v/checker/tests/fixed_array_conv.vv:5:4: error: mismatched types `&int` and
       |    ^
     6 | _ = &int(arr)
     7 | _ = p
+vlib/v/checker/tests/fixed_array_conv.vv:5:6: error: cannot assign to `ip`: expected `&int`, not `[2]int`
+    3 | p = arr
+    4 | mut ip := &int(0)
+    5 | ip = arr
+      |      ~~~
+    6 | _ = &int(arr)
+    7 | _ = p
 vlib/v/checker/tests/fixed_array_conv.vv:11:13: error: cannot use `[2]int` as `voidptr` in argument 1 to `memdup`
     9 | 
    10 | unsafe {
diff --git a/vlib/v/checker/tests/fixed_array_decompose_err.out b/vlib/v/checker/tests/fixed_array_decompose_err.out
index 5c4a87c89d..a188195cfa 100644
--- a/vlib/v/checker/tests/fixed_array_decompose_err.out
+++ b/vlib/v/checker/tests/fixed_array_decompose_err.out
@@ -4,3 +4,9 @@ vlib/v/checker/tests/fixed_array_decompose_err.vv:11:9: error: direct decomposit
    11 |     sum(...arr)
       |            ~~~
    12 | }
+vlib/v/checker/tests/fixed_array_decompose_err.vv:11:6: error: `ast.ArrayDecompose` (no value) used as value in argument 1 to `sum`
+    9 | fn main() {
+   10 |     arr := [1, 2, 3, 4]!
+   11 |     sum(...arr)
+      |         ~~~~~~
+   12 | }
diff --git a/vlib/v/checker/tests/fixed_array_non_const_size_err.out b/vlib/v/checker/tests/fixed_array_non_const_size_err.out
index 073492085f..85bbb57edb 100644
--- a/vlib/v/checker/tests/fixed_array_non_const_size_err.out
+++ b/vlib/v/checker/tests/fixed_array_non_const_size_err.out
@@ -1,7 +1,14 @@
 vlib/v/checker/tests/fixed_array_non_const_size_err.vv:4:12: error: non-constant array bound `size`
     2 |     size := 2
-    3 |
+    3 | 
     4 |     array := [size]int{}
       |               ~~~~
-    5 |
+    5 | 
+    6 |     println(array)
+vlib/v/checker/tests/fixed_array_non_const_size_err.vv:4:12: error: fixed size cannot be zero or negative (fixed_size: 0)
+    2 |     size := 2
+    3 | 
+    4 |     array := [size]int{}
+      |               ~~~~
+    5 | 
     6 |     println(array)
diff --git a/vlib/v/checker/tests/fn_call_with_extra_parenthesis.out b/vlib/v/checker/tests/fn_call_with_extra_parenthesis.out
index 75449fc204..cfcb5c87f2 100644
--- a/vlib/v/checker/tests/fn_call_with_extra_parenthesis.out
+++ b/vlib/v/checker/tests/fn_call_with_extra_parenthesis.out
@@ -1,6 +1,12 @@
 vlib/v/checker/tests/fn_call_with_extra_parenthesis.vv:5:7: error: expected 1 arguments, but got 0
-    3 |
+    3 | 
     4 | fn main() {
     5 |     main.doit()(1)
       |          ~~~~~~
     6 | }
+vlib/v/checker/tests/fn_call_with_extra_parenthesis.vv:5:14: error: unknown function: 
+    3 | 
+    4 | fn main() {
+    5 |     main.doit()(1)
+      |                 ^
+    6 | }
diff --git a/vlib/v/checker/tests/fn_init_sig.out b/vlib/v/checker/tests/fn_init_sig.out
index 08cb17b952..43a45ea156 100644
--- a/vlib/v/checker/tests/fn_init_sig.out
+++ b/vlib/v/checker/tests/fn_init_sig.out
@@ -10,3 +10,10 @@ vlib/v/checker/tests/fn_init_sig.vv:4:1: error: fn `init` must not be public
       | ~~~~~~~~~~~~~~~~~
     5 |     return 1
     6 | }
+vlib/v/checker/tests/fn_init_sig.vv:4:1: error: fn `init` cannot have a return type
+    2 |     return 1
+    3 | }
+    4 | pub fn init() int {
+      | ~~~~~~~~~~~~~~~~~
+    5 |     return 1
+    6 | }
diff --git a/vlib/v/checker/tests/fn_param_import_sym_conflict.out b/vlib/v/checker/tests/fn_param_import_sym_conflict.out
index 548101e99f..355ee576a9 100644
--- a/vlib/v/checker/tests/fn_param_import_sym_conflict.out
+++ b/vlib/v/checker/tests/fn_param_import_sym_conflict.out
@@ -14,10 +14,10 @@ vlib/v/checker/tests/fn_param_import_sym_conflict.vv:3:8: warning: module 'strs
     2 | import maps
     3 | import strings as strs
       |        ~~~~~~~
-    4 |
+    4 | 
     5 | // FnDecl
 vlib/v/checker/tests/fn_param_import_sym_conflict.vv:6:6: error: duplicate of an import symbol `arrays`
-    4 |
+    4 | 
     5 | // FnDecl
     6 | fn x(arrays []int) {
       |      ~~~~~~
@@ -25,49 +25,63 @@ vlib/v/checker/tests/fn_param_import_sym_conflict.vv:6:6: error: duplicate of an
     8 |
 vlib/v/checker/tests/fn_param_import_sym_conflict.vv:9:1: error: duplicate of an import symbol `maps`
     7 | }
-    8 |
+    8 | 
     9 | fn maps() {
       | ~~~~~~~~~
    10 | }
    11 |
 vlib/v/checker/tests/fn_param_import_sym_conflict.vv:12:9: error: duplicate of an import symbol `arrays`
    10 | }
-   11 |
+   11 | 
    12 | fn maps(arrays []int) {
       |         ~~~~~~
    13 | }
    14 |
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:12:1: error: duplicate of an import symbol `maps`
+   10 | }
+   11 | 
+   12 | fn maps(arrays []int) {
+      | ~~~~~~~~~~~~~~~~~~~~~
+   13 | }
+   14 |
 vlib/v/checker/tests/fn_param_import_sym_conflict.vv:18:1: error: duplicate of an import symbol `strs`
    16 | }
-   17 |
+   17 | 
    18 | fn strs() {
       | ~~~~~~~~~
    19 | }
    20 |
 vlib/v/checker/tests/fn_param_import_sym_conflict.vv:24:5: error: duplicate of an import symbol `arrays`
    22 | struct Foo {}
-   23 |
+   23 | 
    24 | fn (arrays Foo) x() {
       |     ~~~~~~
    25 | }
    26 |
 vlib/v/checker/tests/fn_param_import_sym_conflict.vv:27:5: error: duplicate of an import symbol `arrays`
    25 | }
-   26 |
+   26 | 
    27 | fn (arrays Foo) y(maps []int) {
       |     ~~~~~~
    28 | }
    29 |
-vlib/v/checker/tests/fn_param_import_sym_conflict.vv:30:16: error: duplicate of an import symbol `arrays`
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:27:19: error: duplicate of an import symbol `maps`
+   25 | }
+   26 | 
+   27 | fn (arrays Foo) y(maps []int) {
+      |                   ~~~~
    28 | }
    29 |
+vlib/v/checker/tests/fn_param_import_sym_conflict.vv:30:16: error: duplicate of an import symbol `arrays`
+   28 | }
+   29 | 
    30 | fn (foo Foo) z(arrays []int) {
       |                ~~~~~~
    31 | }
    32 |
 vlib/v/checker/tests/fn_param_import_sym_conflict.vv:33:5: error: duplicate of an import symbol `arrays`
    31 | }
-   32 |
+   32 | 
    33 | fn (arrays Foo) maps() {
       |     ~~~~~~
    34 | }
@@ -77,4 +91,4 @@ vlib/v/checker/tests/fn_param_import_sym_conflict.vv:47:11: error: duplicate of
    46 | fn y() {
    47 |     _ := fn (arrays []int) {}
       |              ~~~~~~
-   48 | }
\ No newline at end of file
+   48 | }
diff --git a/vlib/v/checker/tests/fn_type_exists.out b/vlib/v/checker/tests/fn_type_exists.out
index c6aa40fcc0..46348bb6fa 100644
--- a/vlib/v/checker/tests/fn_type_exists.out
+++ b/vlib/v/checker/tests/fn_type_exists.out
@@ -1,10 +1,15 @@
 vlib/v/checker/tests/fn_type_exists.vv:1:34: error: unknown type `Pants`
     1 | type PantsCreator = fn (a Shirt) Pants
       |                                  ~~~~~
-    2 |
+    2 | 
+    3 | type PantsConsumer = fn (p Pants)
+vlib/v/checker/tests/fn_type_exists.vv:1:27: error: unknown type `Shirt`
+    1 | type PantsCreator = fn (a Shirt) Pants
+      |                           ~~~~~
+    2 | 
     3 | type PantsConsumer = fn (p Pants)
 vlib/v/checker/tests/fn_type_exists.vv:3:28: error: unknown type `Pants`
     1 | type PantsCreator = fn (a Shirt) Pants
-    2 |
+    2 | 
     3 | type PantsConsumer = fn (p Pants)
-      |                            ~~~~~
\ No newline at end of file
+      |                            ~~~~~
diff --git a/vlib/v/checker/tests/fn_type_mismatch.out b/vlib/v/checker/tests/fn_type_mismatch.out
index 922c19abcf..a9a71f0a69 100644
--- a/vlib/v/checker/tests/fn_type_mismatch.out
+++ b/vlib/v/checker/tests/fn_type_mismatch.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/fn_type_mismatch.vv:11:15: error: invalid array element: expected `fn (int, int) f32`, not `fn (f32, f32) f32`
-    9 |
+    9 | 
    10 | fn main() {
    11 |     fns := [add, div]
       |                  ~~~
@@ -12,9 +12,22 @@ vlib/v/checker/tests/fn_type_mismatch.vv:12:17: error: cannot use `float literal
       |                    ~~~~
    13 |     println(fns[1](10.0, 5.0))
    14 | }
+vlib/v/checker/tests/fn_type_mismatch.vv:12:23: error: cannot use `float literal` as `int` in argument 2 to ``
+   10 | fn main() {
+   11 |     fns := [add, div]
+   12 |     println(fns[0](10.0, 5.0))
+      |                          ~~~
+   13 |     println(fns[1](10.0, 5.0))
+   14 | }
 vlib/v/checker/tests/fn_type_mismatch.vv:13:17: error: cannot use `float literal` as `int` in argument 1 to ``
    11 |     fns := [add, div]
    12 |     println(fns[0](10.0, 5.0))
    13 |     println(fns[1](10.0, 5.0))
       |                    ~~~~
    14 | }
+vlib/v/checker/tests/fn_type_mismatch.vv:13:23: error: cannot use `float literal` as `int` in argument 2 to ``
+   11 |     fns := [add, div]
+   12 |     println(fns[0](10.0, 5.0))
+   13 |     println(fns[1](10.0, 5.0))
+      |                          ~~~
+   14 | }
diff --git a/vlib/v/checker/tests/fn_var.out b/vlib/v/checker/tests/fn_var.out
index be5cf19f41..93b67786eb 100644
--- a/vlib/v/checker/tests/fn_var.out
+++ b/vlib/v/checker/tests/fn_var.out
@@ -22,6 +22,12 @@ vlib/v/checker/tests/fn_var.vv:9:10: error: undefined ident: `i`
     9 |     println(i)
       |             ^
    10 | }
+vlib/v/checker/tests/fn_var.vv:9:2: error: `println` can not print void expressions
+    7 | println(i)
+    8 | f = fn (mut a []int) {
+    9 |     println(i)
+      |     ~~~~~~~~~~
+   10 | }
 vlib/v/checker/tests/fn_var.vv:8:5: error: cannot assign to `f`: expected `fn (int) u8`, not `fn (mut []int)`
     6 | i := 0
     7 | println(i)
diff --git a/vlib/v/checker/tests/for_in_invalid_identifier.out b/vlib/v/checker/tests/for_in_invalid_identifier.out
index 79115d7d71..89c30146ef 100644
--- a/vlib/v/checker/tests/for_in_invalid_identifier.out
+++ b/vlib/v/checker/tests/for_in_invalid_identifier.out
@@ -4,10 +4,16 @@ vlib/v/checker/tests/for_in_invalid_identifier.vv:2:26: error: undefined ident:
       |                             ^
     3 |         println('Hello $index $value')
     4 |     }
+vlib/v/checker/tests/for_in_invalid_identifier.vv:2:28: error: `s` does not return a value
+    1 | fn main() {
+    2 |     for index, mut value in s.statements {
+      |                               ~~~~~~~~~~
+    3 |         println('Hello $index $value')
+    4 |     }
 vlib/v/checker/tests/for_in_invalid_identifier.vv:3:26: error: no known default format for type `void`
     1 | fn main() {
     2 |     for index, mut value in s.statements {
     3 |         println('Hello $index $value')
       |                                ~~~~~
     4 |     }
-    5 | }
\ No newline at end of file
+    5 | }
diff --git a/vlib/v/checker/tests/free_method_errors.out b/vlib/v/checker/tests/free_method_errors.out
index 2b3376d031..20dfce3aa5 100644
--- a/vlib/v/checker/tests/free_method_errors.out
+++ b/vlib/v/checker/tests/free_method_errors.out
@@ -12,6 +12,13 @@ vlib/v/checker/tests/free_method_errors.vv:7:23: error: `.free()` methods should
       |                       ~~~
     8 | 
     9 | struct Error3 {}
+vlib/v/checker/tests/free_method_errors.vv:7:1: error: missing return at end of function `free`
+    5 | struct Error2 {}
+    6 | 
+    7 | fn (a &Error2) free() f64 {}
+      | ~~~~~~~~~~~~~~~~~~~~~~~~~
+    8 | 
+    9 | struct Error3 {}
 vlib/v/checker/tests/free_method_errors.vv:11:1: error: `.free()` methods should have 0 arguments
     9 | struct Error3 {}
    10 | 
diff --git a/vlib/v/checker/tests/generic_closure_fn_decl_err_b.out b/vlib/v/checker/tests/generic_closure_fn_decl_err_b.out
index 807e4bba7a..7918f0165e 100644
--- a/vlib/v/checker/tests/generic_closure_fn_decl_err_b.out
+++ b/vlib/v/checker/tests/generic_closure_fn_decl_err_b.out
@@ -1,7 +1,14 @@
 vlib/v/checker/tests/generic_closure_fn_decl_err_b.vv:13:2: error: generic closure fn must specify type parameter, e.g. fn [foo] [T]()
    11 |     println(typeof(my_plugin).name) // MyPlugin
-   12 |
+   12 | 
    13 |     fn[my_plugin](){ my_plugin.on_update() }()
       |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    14 | }
    15 |
+vlib/v/checker/tests/generic_closure_fn_decl_err_b.vv:13:29: error: unknown method or field: `T.on_update`
+   11 |     println(typeof(my_plugin).name) // MyPlugin
+   12 | 
+   13 |     fn[my_plugin](){ my_plugin.on_update() }()
+      |                                ~~~~~~~~~~~
+   14 | }
+   15 |
diff --git a/vlib/v/checker/tests/generic_fn_decl_err.out b/vlib/v/checker/tests/generic_fn_decl_err.out
index bd331c0157..45f5fbbfb8 100644
--- a/vlib/v/checker/tests/generic_fn_decl_err.out
+++ b/vlib/v/checker/tests/generic_fn_decl_err.out
@@ -1,34 +1,34 @@
 vlib/v/checker/tests/generic_fn_decl_err.vv:19:29: error: generic type name `P` is not mentioned in fn `create1[U]`
    17 | }
-   18 |
+   18 | 
    19 | fn (r Db) create1<U>(u U, p P) {
       |                             ^
    20 |     println('Yo')
    21 | }
 vlib/v/checker/tests/generic_fn_decl_err.vv:23:29: error: generic type name `P` is not mentioned in fn `create2[U]`
    21 | }
-   22 |
+   22 | 
    23 | fn (r Db) create2<U>(u U, p &P) {
       |                             ~~
    24 |     println('Yo')
    25 | }
 vlib/v/checker/tests/generic_fn_decl_err.vv:27:29: error: generic type name `P` is not mentioned in fn `create3[U]`
    25 | }
-   26 |
+   26 | 
    27 | fn (r Db) create3<U>(u U, p []P) {
       |                             ~~~
    28 |     println('Yo')
    29 | }
 vlib/v/checker/tests/generic_fn_decl_err.vv:31:27: error: generic type name `P` is not mentioned in fn `create4[U]`
    29 | }
-   30 |
+   30 | 
    31 | fn (r Db) create4<U>(u U) P {
       |                           ^
    32 |     return P{}
    33 | }
 vlib/v/checker/tests/generic_fn_decl_err.vv:35:27: error: generic type name `P` is not mentioned in fn `create5[U]`
    33 | }
-   34 |
+   34 | 
    35 | fn (r Db) create5<U>(u U) []P {
       |                           ~~~
    36 |     return [P{}]
diff --git a/vlib/v/checker/tests/generic_fn_decl_without_generic_names_err.out b/vlib/v/checker/tests/generic_fn_decl_without_generic_names_err.out
index 40eeb22218..95eec22236 100644
--- a/vlib/v/checker/tests/generic_fn_decl_without_generic_names_err.out
+++ b/vlib/v/checker/tests/generic_fn_decl_without_generic_names_err.out
@@ -1,24 +1,45 @@
 vlib/v/checker/tests/generic_fn_decl_without_generic_names_err.vv:26:1: error: generic function declaration must specify generic type names
    24 | }
-   25 |
+   25 | 
    26 | fn g_worker(g Generic[T]) {
       | ~~~~~~~~~~~~~~~~~~~~~~~~~
    27 |     t := <-g.ch
    28 |     handle(t)
 Details: use `fn foo[T](x T) {`, not just `fn foo(x T) {`
+vlib/v/checker/tests/generic_fn_decl_without_generic_names_err.vv:26:15: error: generic type name `T` is not mentioned in fn `g_worker[]`
+   24 | }
+   25 | 
+   26 | fn g_worker(g Generic[T]) {
+      |               ~~~~~~~~~~
+   27 |     t := <-g.ch
+   28 |     handle(t)
 vlib/v/checker/tests/generic_fn_decl_without_generic_names_err.vv:32:1: error: generic function declaration must specify generic type names
    30 | }
-   31 |
+   31 | 
    32 | fn handle(t T) {
       | ~~~~~~~~~~~~~~
    33 |     println('hi')
    34 | }
 Details: use `fn foo[T](x T) {`, not just `fn foo(x T) {`
+vlib/v/checker/tests/generic_fn_decl_without_generic_names_err.vv:32:13: error: generic type name `T` is not mentioned in fn `handle[]`
+   30 | }
+   31 | 
+   32 | fn handle(t T) {
+      |             ^
+   33 |     println('hi')
+   34 | }
 vlib/v/checker/tests/generic_fn_decl_without_generic_names_err.vv:40:1: error: generic method declaration must specify generic type names
    38 | type MayBe[T] = None | T
-   39 |
+   39 | 
    40 | fn (m MayBe[T]) is_some() bool {
       | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    41 |     return m is T
    42 | }
 Details: use `fn (r SomeType[T]) foo[T]() {`, not just `fn (r SomeType[T]) foo() {`
+vlib/v/checker/tests/generic_fn_decl_without_generic_names_err.vv:40:7: error: generic type name `T` is not mentioned in fn `is_some[]`
+   38 | type MayBe[T] = None | T
+   39 | 
+   40 | fn (m MayBe[T]) is_some() bool {
+      |       ~~~~~~~~
+   41 |     return m is T
+   42 | }
diff --git a/vlib/v/checker/tests/generic_interface_err.out b/vlib/v/checker/tests/generic_interface_err.out
index 007bc890f7..10030574f5 100644
--- a/vlib/v/checker/tests/generic_interface_err.out
+++ b/vlib/v/checker/tests/generic_interface_err.out
@@ -1,16 +1,21 @@
 vlib/v/checker/tests/generic_interface_err.vv:10:1: warning: unused variable: `i`
-    8 |
+    8 | 
     9 | s := Struct{7}
    10 | i := Interface(s)
       | ^
 vlib/v/checker/tests/generic_interface_err.vv:9:6: error: could not infer generic type `T` in generic struct `Struct[T]`
     7 | }
-    8 |
+    8 | 
     9 | s := Struct{7}
       |      ~~~~~~~~~
    10 | i := Interface(s)
 vlib/v/checker/tests/generic_interface_err.vv:10:6: error: can not find method `method` on `Struct`, needed for interface: `Interface`
-    8 |
+    8 | 
+    9 | s := Struct{7}
+   10 | i := Interface(s)
+      |      ~~~~~~~~~~~~
+vlib/v/checker/tests/generic_interface_err.vv:10:6: error: `Struct` does not implement interface `Interface`, cannot cast `Struct` to interface `Interface`
+    8 | 
     9 | s := Struct{7}
    10 | i := Interface(s)
       |      ~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/generic_sumtype_decl_err_a.out b/vlib/v/checker/tests/generic_sumtype_decl_err_a.out
index 368b71042b..b828c26b07 100644
--- a/vlib/v/checker/tests/generic_sumtype_decl_err_a.out
+++ b/vlib/v/checker/tests/generic_sumtype_decl_err_a.out
@@ -1,7 +1,14 @@
 vlib/v/checker/tests/generic_sumtype_decl_err_a.vv:7:24: error: generic struct `Just` must specify generic type names, e.g. Just[T]
     5 | struct Nothing {}
-    6 |
+    6 | 
     7 | type Maybe = Nothing | Just
       |                        ~~~~
-    8 |
+    8 | 
+    9 | fn main() {
+vlib/v/checker/tests/generic_sumtype_decl_err_a.vv:7:6: error: generic sumtype `Maybe` must specify generic type names, e.g. Maybe[T]
+    5 | struct Nothing {}
+    6 | 
+    7 | type Maybe = Nothing | Just
+      |      ~~~~~
+    8 | 
     9 | fn main() {
diff --git a/vlib/v/checker/tests/generic_sumtype_decl_err_d.out b/vlib/v/checker/tests/generic_sumtype_decl_err_d.out
index a748a26e06..8489cf74f1 100644
--- a/vlib/v/checker/tests/generic_sumtype_decl_err_d.out
+++ b/vlib/v/checker/tests/generic_sumtype_decl_err_d.out
@@ -1,7 +1,14 @@
 vlib/v/checker/tests/generic_sumtype_decl_err_d.vv:5:15: error: generic fntype `Fn` must specify generic type names, e.g. Fn[T]
     3 | type Fnn = fn (string) string
-    4 |
+    4 | 
     5 | type Parser = Fn | Fnn
       |               ~~
-    6 |
+    6 | 
+    7 | fn main() {
+vlib/v/checker/tests/generic_sumtype_decl_err_d.vv:5:6: error: generic sumtype `Parser` must specify generic type names, e.g. Parser[T]
+    3 | type Fnn = fn (string) string
+    4 | 
+    5 | type Parser = Fn | Fnn
+      |      ~~~~~~
+    6 | 
     7 | fn main() {
diff --git a/vlib/v/checker/tests/generic_type_name_in_non_generic_function.out b/vlib/v/checker/tests/generic_type_name_in_non_generic_function.out
index c4db510710..fa68c3c999 100644
--- a/vlib/v/checker/tests/generic_type_name_in_non_generic_function.out
+++ b/vlib/v/checker/tests/generic_type_name_in_non_generic_function.out
@@ -5,3 +5,31 @@ vlib/v/checker/tests/generic_type_name_in_non_generic_function.vv:3:10: error: u
       |             ^
     4 |         println('yes')
     5 |     } else {
+vlib/v/checker/tests/generic_type_name_in_non_generic_function.vv:3:20: error: undefined ident: `Z`
+    1 | fn main() {
+    2 |     c := u8(`D`)
+    3 |     if c >= A && c <= Z {
+      |                       ^
+    4 |         println('yes')
+    5 |     } else {
+vlib/v/checker/tests/generic_type_name_in_non_generic_function.vv:3:5: error: left operand for `&&` is not a boolean
+    1 | fn main() {
+    2 |     c := u8(`D`)
+    3 |     if c >= A && c <= Z {
+      |        ~~~~~~
+    4 |         println('yes')
+    5 |     } else {
+vlib/v/checker/tests/generic_type_name_in_non_generic_function.vv:3:15: error: right operand for `&&` is not a boolean
+    1 | fn main() {
+    2 |     c := u8(`D`)
+    3 |     if c >= A && c <= Z {
+      |                  ~~~~~~
+    4 |         println('yes')
+    5 |     } else {
+vlib/v/checker/tests/generic_type_name_in_non_generic_function.vv:3:5: error: non-bool type `void` used as if condition
+    1 | fn main() {
+    2 |     c := u8(`D`)
+    3 |     if c >= A && c <= Z {
+      |        ~~~~~~~~~~~~~~~~
+    4 |         println('yes')
+    5 |     } else {
diff --git a/vlib/v/checker/tests/generics_fn_arguments_count_err.out b/vlib/v/checker/tests/generics_fn_arguments_count_err.out
index 62cb366698..752bd5dbdb 100644
--- a/vlib/v/checker/tests/generics_fn_arguments_count_err.out
+++ b/vlib/v/checker/tests/generics_fn_arguments_count_err.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/generics_fn_arguments_count_err.vv:12:18: error: expected 2 generic parameters, got 1
-   10 |
+   10 | 
    11 | fn main() {
    12 |     ret1 := get_name<int>(11, 22)
       |                     ~~~~~
@@ -7,13 +7,20 @@ vlib/v/checker/tests/generics_fn_arguments_count_err.vv:12:18: error: expected 2
    14 |
 vlib/v/checker/tests/generics_fn_arguments_count_err.vv:15:18: error: expected 2 generic parameters, got 3
    13 |     println(ret1)
-   14 |
+   14 | 
    15 |     ret2 := get_name<int, int, string>(11, 22, 'hello')
       |                     ~~~~~~~~~~~~~~~~~~
    16 |     println(ret2)
    17 |
-vlib/v/checker/tests/generics_fn_arguments_count_err.vv:19:22: error: expected 2 generic parameters, got 1
+vlib/v/checker/tests/generics_fn_arguments_count_err.vv:15:45: error: expected 2 arguments, but got 3
+   13 |     println(ret1)
+   14 | 
+   15 |     ret2 := get_name<int, int, string>(11, 22, 'hello')
+      |                                                ~~~~~~~
+   16 |     println(ret2)
    17 |
+vlib/v/checker/tests/generics_fn_arguments_count_err.vv:19:22: error: expected 2 generic parameters, got 1
+   17 | 
    18 |     foo := Foo{}
    19 |     ret3 := foo.get_name<int>(11, 22)
       |                         ~~~~~
@@ -21,21 +28,41 @@ vlib/v/checker/tests/generics_fn_arguments_count_err.vv:19:22: error: expected 2
    21 |
 vlib/v/checker/tests/generics_fn_arguments_count_err.vv:22:22: error: expected 2 generic parameters, got 3
    20 |     println(ret3)
-   21 |
+   21 | 
    22 |     ret4 := foo.get_name<int, int, string>(11, 22, 'hello')
       |                         ~~~~~~~~~~~~~~~~~~
    23 |     println(ret4)
    24 | }
+vlib/v/checker/tests/generics_fn_arguments_count_err.vv:22:49: error: expected 2 arguments, but got 3
+   20 |     println(ret3)
+   21 | 
+   22 |     ret4 := foo.get_name<int, int, string>(11, 22, 'hello')
+      |                                                    ~~~~~~~
+   23 |     println(ret4)
+   24 | }
 vlib/v/checker/tests/generics_fn_arguments_count_err.vv:2:11: error: no known default format for type `A`
     1 | fn get_name<A, B>(a A, b B) string {
     2 |     return '$a, $b'
       |              ^
     3 | }
     4 |
+vlib/v/checker/tests/generics_fn_arguments_count_err.vv:2:15: error: no known default format for type `B`
+    1 | fn get_name<A, B>(a A, b B) string {
+    2 |     return '$a, $b'
+      |                  ^
+    3 | }
+    4 |
 vlib/v/checker/tests/generics_fn_arguments_count_err.vv:8:11: error: no known default format for type `A`
-    6 |
+    6 | 
     7 | fn (f Foo) get_name<A, B>(a A, b B) string {
     8 |     return '$a, $b'
       |              ^
     9 | }
    10 |
+vlib/v/checker/tests/generics_fn_arguments_count_err.vv:8:15: error: no known default format for type `B`
+    6 | 
+    7 | fn (f Foo) get_name<A, B>(a A, b B) string {
+    8 |     return '$a, $b'
+      |                  ^
+    9 | }
+   10 |
diff --git a/vlib/v/checker/tests/generics_fn_return_generic_struct_err.out b/vlib/v/checker/tests/generics_fn_return_generic_struct_err.out
index 47cb85524e..c7508524a0 100644
--- a/vlib/v/checker/tests/generics_fn_return_generic_struct_err.out
+++ b/vlib/v/checker/tests/generics_fn_return_generic_struct_err.out
@@ -1,12 +1,12 @@
 vlib/v/checker/tests/generics_fn_return_generic_struct_err.vv:13:32: error: return generic struct `GenericChannelStruct` in fn declaration must specify the generic type names, e.g. GenericChannelStruct[T]
    11 | }
-   12 |
+   12 | 
    13 | pub fn new_channel_struct[T]() GenericChannelStruct {
       |                                ~~~~~~~~~~~~~~~~~~~~
    14 |     d := GenericChannelStruct{
    15 |         ch: chan T{}
 vlib/v/checker/tests/generics_fn_return_generic_struct_err.vv:14:7: error: generic struct init must specify type parameter, e.g. Foo[T]
-   12 |
+   12 | 
    13 | pub fn new_channel_struct[T]() GenericChannelStruct {
    14 |     d := GenericChannelStruct{
       |          ~~~~~~~~~~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/generics_struct_init_err.out b/vlib/v/checker/tests/generics_struct_init_err.out
index 9fab5e57bf..a729f888c4 100644
--- a/vlib/v/checker/tests/generics_struct_init_err.out
+++ b/vlib/v/checker/tests/generics_struct_init_err.out
@@ -19,6 +19,13 @@ vlib/v/checker/tests/generics_struct_init_err.vv:67:8: error: could not infer ge
       |           ~~~~~~~~~~~~~~
    68 |     assert ret == -6
    69 | }
+vlib/v/checker/tests/generics_struct_init_err.vv:67:23: error: could not infer generic type `T` in call to `call`
+   65 |     ret = holder_call_22(neg, 5)
+   66 |     assert ret == -5
+   67 |     ret = FnHolder2{neg}.call(6)
+      |                          ~~~~~~~
+   68 |     assert ret == -6
+   69 | }
 vlib/v/checker/tests/generics_struct_init_err.vv:22:7: error: generic struct init must specify type parameter, e.g. Foo[T]
    20 | 
    21 | fn holder_call_1[T](func T, a int) int {
diff --git a/vlib/v/checker/tests/generics_struct_init_type_parameter_err.out b/vlib/v/checker/tests/generics_struct_init_type_parameter_err.out
index 269e14d0c3..9076777f51 100644
--- a/vlib/v/checker/tests/generics_struct_init_type_parameter_err.out
+++ b/vlib/v/checker/tests/generics_struct_init_type_parameter_err.out
@@ -1,12 +1,12 @@
 vlib/v/checker/tests/generics_struct_init_type_parameter_err.vv:6:9: error: generic struct init type parameter `U` must be within the parameters `(A,B)` of the current generic function
-    4 |
+    4 | 
     5 | fn send_1<A, B>(res A, b B) string {
     6 |     msg := Response<U>{
       |            ~~~~~~~~~~~~
     7 |         result: res
     8 |     }
 vlib/v/checker/tests/generics_struct_init_type_parameter_err.vv:14:9: error: generic struct init expects 1 generic parameter, but got 2
-   12 |
+   12 | 
    13 | fn send_2<A, B>(res A, b B) string {
    14 |     msg := Response<A, B>{
       |            ~~~~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/go_wait_or.out b/vlib/v/checker/tests/go_wait_or.out
index 55372c8dac..769a8d0119 100644
--- a/vlib/v/checker/tests/go_wait_or.out
+++ b/vlib/v/checker/tests/go_wait_or.out
@@ -33,6 +33,13 @@ vlib/v/checker/tests/go_wait_or.vv:25:6: error: `.wait()` cannot be called for a
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    26 |     for t in tg3 {
    27 |         a := t.wait()
+vlib/v/checker/tests/go_wait_or.vv:25:13: error: unexpected `or` block, the function `wait` does not return an Option or a Result
+   23 |         spawn f(1)
+   24 |     ]
+   25 |     tg3.wait() or { panic('problem') }
+      |                ~~~~~~~~~~~~~~~~~~~~~~~
+   26 |     for t in tg3 {
+   27 |         a := t.wait()
 vlib/v/checker/tests/go_wait_or.vv:38:6: error: `.wait()` cannot be called for an array when thread functions return options. Iterate over the arrays elements instead and handle each returned option with `or`.
    36 |         spawn g(1)
    37 |     ]
diff --git a/vlib/v/checker/tests/goto_label.out b/vlib/v/checker/tests/goto_label.out
index 985b6889a6..b4a0bf4ad7 100644
--- a/vlib/v/checker/tests/goto_label.out
+++ b/vlib/v/checker/tests/goto_label.out
@@ -1,77 +1,77 @@
-vlib/v/checker/tests/goto_label.vv:7:8: warning: `goto` requires `unsafe` (consider using labelled break/continue)
-    5 |     goto a1
-    6 |     _ = fn(){
-    7 |         goto f1
+vlib/v/checker/tests/goto_label.vv:8:9: warning: `goto` requires `unsafe` (consider using labelled break/continue)
+    6 |         goto a1
+    7 |         _ = fn () {
+    8 |             goto f1 // the `f1` label is not available here; it is in the outer scope
+      |                  ~~
+    9 |             goto f2 // same with `f2`
+   10 |             goto a1 // this is ok
+vlib/v/checker/tests/goto_label.vv:9:9: warning: `goto` requires `unsafe` (consider using labelled break/continue)
+    7 |         _ = fn () {
+    8 |             goto f1 // the `f1` label is not available here; it is in the outer scope
+    9 |             goto f2 // same with `f2`
+      |                  ~~
+   10 |             goto a1 // this is ok
+   11 |             a1:
+vlib/v/checker/tests/goto_label.vv:10:9: warning: `goto` requires `unsafe` (consider using labelled break/continue)
+    8 |             goto f1 // the `f1` label is not available here; it is in the outer scope
+    9 |             goto f2 // same with `f2`
+   10 |             goto a1 // this is ok
+      |                  ~~
+   11 |             a1:
+   12 |             goto a1
+vlib/v/checker/tests/goto_label.vv:12:9: warning: `goto` requires `unsafe` (consider using labelled break/continue)
+   10 |             goto a1 // this is ok
+   11 |             a1:
+   12 |             goto a1
+      |                  ~~
+   13 |         }
+   14 |         f2:
+vlib/v/checker/tests/goto_label.vv:6:8: error: unknown label `a1`
+    4 |         goto f2
+    5 |         f1:
+    6 |         goto a1
       |              ~~
-    8 |         goto f2
-    9 |         goto a1
-vlib/v/checker/tests/goto_label.vv:8:8: warning: `goto` requires `unsafe` (consider using labelled break/continue)
-    6 |     _ = fn(){
-    7 |         goto f1
-    8 |         goto f2
+    7 |         _ = fn () {
+    8 |             goto f1 // the `f1` label is not available here; it is in the outer scope
+vlib/v/checker/tests/goto_label.vv:8:9: error: unknown label `f1`
+    6 |         goto a1
+    7 |         _ = fn () {
+    8 |             goto f1 // the `f1` label is not available here; it is in the outer scope
+      |                  ~~
+    9 |             goto f2 // same with `f2`
+   10 |             goto a1 // this is ok
+vlib/v/checker/tests/goto_label.vv:9:9: error: unknown label `f2`
+    7 |         _ = fn () {
+    8 |             goto f1 // the `f1` label is not available here; it is in the outer scope
+    9 |             goto f2 // same with `f2`
+      |                  ~~
+   10 |             goto a1 // this is ok
+   11 |             a1:
+vlib/v/checker/tests/goto_label.vv:15:8: error: unknown label `a1`
+   13 |         }
+   14 |         f2:
+   15 |         goto a1
       |              ~~
-    9 |         goto a1
-   10 |         a1:
-vlib/v/checker/tests/goto_label.vv:9:8: warning: `goto` requires `unsafe` (consider using labelled break/continue)
-    7 |         goto f1
-    8 |         goto f2
-    9 |         goto a1
+   16 |         goto f1 // back
+   17 |         goto f2
+vlib/v/checker/tests/goto_label.vv:25:8: error: unknown label `f1`
+   23 |         goto g1 // forward
+   24 |         g1:
+   25 |         goto f1
       |              ~~
-   10 |         a1:
-   11 |         goto a1
-vlib/v/checker/tests/goto_label.vv:11:8: warning: `goto` requires `unsafe` (consider using labelled break/continue)
-    9 |         goto a1
-   10 |         a1:
-   11 |         goto a1
+   26 |         goto a1
+   27 |         goto g1 // back
+vlib/v/checker/tests/goto_label.vv:26:8: error: unknown label `a1`
+   24 |         g1:
+   25 |         goto f1
+   26 |         goto a1
       |              ~~
-   12 |     }
-   13 |     f2:
-vlib/v/checker/tests/goto_label.vv:5:7: error: unknown label `a1`
-    3 |     goto f2
-    4 |     f1:
-    5 |     goto a1
-      |          ~~
-    6 |     _ = fn(){
-    7 |         goto f1
-vlib/v/checker/tests/goto_label.vv:7:8: error: unknown label `f1`
-    5 |     goto a1
-    6 |     _ = fn(){
-    7 |         goto f1
-      |              ~~
-    8 |         goto f2
-    9 |         goto a1
-vlib/v/checker/tests/goto_label.vv:8:8: error: unknown label `f2`
-    6 |     _ = fn(){
-    7 |         goto f1
-    8 |         goto f2
-      |              ~~
-    9 |         goto a1
-   10 |         a1:
-vlib/v/checker/tests/goto_label.vv:14:7: error: unknown label `a1`
-   12 |     }
-   13 |     f2:
-   14 |     goto a1
-      |          ~~
-   15 |     goto f1 // back
-   16 |     goto f2
-vlib/v/checker/tests/goto_label.vv:22:7: error: unknown label `f1`
-   20 |     goto g1 // forward
-   21 |     g1:
-   22 |     goto f1
-      |          ~~
-   23 |     goto a1
-   24 |     goto g1 // back
-vlib/v/checker/tests/goto_label.vv:23:7: error: unknown label `a1`
-   21 |     g1:
-   22 |     goto f1
-   23 |     goto a1
-      |          ~~
-   24 |     goto g1 // back
-   25 |     goto undefined
-vlib/v/checker/tests/goto_label.vv:25:7: error: unknown label `undefined`
-   23 |     goto a1
-   24 |     goto g1 // back
-   25 |     goto undefined
-      |          ~~~~~~~~~
-   26 | }}
-   27 |
+   27 |         goto g1 // back
+   28 |         goto undefined
+vlib/v/checker/tests/goto_label.vv:28:8: error: unknown label `undefined`
+   26 |         goto a1
+   27 |         goto g1 // back
+   28 |         goto undefined
+      |              ~~~~~~~~~
+   29 |     }
+   30 | }
diff --git a/vlib/v/checker/tests/goto_label.vv b/vlib/v/checker/tests/goto_label.vv
index 23b2cd75a7..8132250ad7 100644
--- a/vlib/v/checker/tests/goto_label.vv
+++ b/vlib/v/checker/tests/goto_label.vv
@@ -1,29 +1,33 @@
-fn f() {unsafe {
-	goto f1 // forward
-	goto f2
-	f1:
-	goto a1
-	_ = fn(){
-		goto f1
+fn f() {
+	unsafe {
+		goto f1 // forward
 		goto f2
+		f1:
 		goto a1
-		a1:
+		_ = fn () {
+			goto f1 // the `f1` label is not available here; it is in the outer scope
+			goto f2 // same with `f2`
+			goto a1 // this is ok
+			a1:
+			goto a1
+		}
+		f2:
 		goto a1
+		goto f1 // back
+		goto f2
 	}
-	f2:
-	goto a1
-	goto f1 // back
-	goto f2
-}}
+}
 
-fn g() {unsafe {
-	goto g1 // forward
-	g1:
-	goto f1
-	goto a1
-	goto g1 // back
-	goto undefined
-}}
+fn g() {
+	unsafe {
+		goto g1 // forward
+		g1:
+		goto f1
+		goto a1
+		goto g1 // back
+		goto undefined
+	}
+}
 
 // implicit main
 unsafe {
diff --git a/vlib/v/checker/tests/if_match_result.out b/vlib/v/checker/tests/if_match_result.out
index 00c41ad1ee..d9950d4256 100644
--- a/vlib/v/checker/tests/if_match_result.out
+++ b/vlib/v/checker/tests/if_match_result.out
@@ -18,6 +18,13 @@ vlib/v/checker/tests/if_match_result.vv:7:3: error: `if` expression requires an
       |   ~~~~
     8 | }
     9 |
+vlib/v/checker/tests/if_match_result.vv:6:3: error: assignment mismatch: 1 variable(s) 0 value(s)
+    4 |     else {}
+    5 | }
+    6 | _ = if true {
+      |   ^
+    7 | } else {
+    8 | }
 vlib/v/checker/tests/if_match_result.vv:11:3: error: assignment mismatch: 1 variable(s) 0 value(s)
     9 | 
    10 | // void results
diff --git a/vlib/v/checker/tests/immutable_field.out b/vlib/v/checker/tests/immutable_field.out
index 05b62143f5..99dab99a55 100644
--- a/vlib/v/checker/tests/immutable_field.out
+++ b/vlib/v/checker/tests/immutable_field.out
@@ -4,3 +4,9 @@ vlib/v/checker/tests/immutable_field.vv:8:4: error: field `i1` of struct `Aaa` i
     8 |     a.i1 = 2
       |       ~~
     9 | }
+vlib/v/checker/tests/immutable_field.vv:8:2: error: `a` is immutable, declare it with `mut` to make it mutable
+    6 | fn main() {
+    7 |     a := Aaa{1}
+    8 |     a.i1 = 2
+      |     ^
+    9 | }
diff --git a/vlib/v/checker/tests/import_mod_duplicate_err.out b/vlib/v/checker/tests/import_mod_duplicate_err.out
index 212aed5530..74276419eb 100644
--- a/vlib/v/checker/tests/import_mod_duplicate_err.out
+++ b/vlib/v/checker/tests/import_mod_duplicate_err.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/import_mod_duplicate_err.vv:3:8: error: cannot import `json
       |        ~~~~
     4 | 
     5 | const used = true
+vlib/v/checker/tests/import_mod_duplicate_err.vv:3:8: error: cannot import `json` as `json` into a module with the same name
+    1 | module json
+    2 | 
+    3 | import json
+      |        ~~~~
+    4 | 
+    5 | const used = true
 vlib/v/checker/tests/import_mod_duplicate_err.vv:1:1: error: project must include a `main` module or be a shared library (compile with `v -shared`)
     1 | module json
       | ^
diff --git a/vlib/v/checker/tests/import_mod_sub_duplicate_err.out b/vlib/v/checker/tests/import_mod_sub_duplicate_err.out
index 735cd71abc..5c9164c34e 100644
--- a/vlib/v/checker/tests/import_mod_sub_duplicate_err.out
+++ b/vlib/v/checker/tests/import_mod_sub_duplicate_err.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/import_mod_sub_duplicate_err.vv:3:8: error: cannot import `
       |        ~~~~~~~
     4 | 
     5 | println(json2.Any(json2.null))
+vlib/v/checker/tests/import_mod_sub_duplicate_err.vv:3:10: error: cannot import `x.json2` as `json2` into a module with the same name
+    1 | module json2
+    2 | 
+    3 | import x.json2
+      |          ~~~~~
+    4 | 
+    5 | println(json2.Any(json2.null))
 vlib/v/checker/tests/import_mod_sub_duplicate_err.vv:1:1: error: project must include a `main` module or be a shared library (compile with `v -shared`)
     1 | module json2
       | ^
diff --git a/vlib/v/checker/tests/import_symbol_private_err.out b/vlib/v/checker/tests/import_symbol_private_err.out
index 61b570c6d1..91ad47b3a9 100644
--- a/vlib/v/checker/tests/import_symbol_private_err.out
+++ b/vlib/v/checker/tests/import_symbol_private_err.out
@@ -58,3 +58,9 @@ vlib/v/checker/tests/import_symbol_private_err.vv:13:6: error: struct `io.Reader
    13 |     _ = ReaderWriterImpl{}
       |         ~~~~~~~~~~~~~~~~~~
    14 | }
+vlib/v/checker/tests/import_symbol_private_err.vv:13:6: error: type `io.ReaderWriterImpl` is private
+   11 |         'h': 2
+   12 |     }.exists('h')
+   13 |     _ = ReaderWriterImpl{}
+      |         ~~~~~~~~~~~~~~~~~~
+   14 | }
diff --git a/vlib/v/checker/tests/import_symbol_type_err.out b/vlib/v/checker/tests/import_symbol_type_err.out
index 2c1cd9be8c..3da58eaa9a 100644
--- a/vlib/v/checker/tests/import_symbol_type_err.out
+++ b/vlib/v/checker/tests/import_symbol_type_err.out
@@ -10,3 +10,15 @@ Did you mean `crypto.Hash`?
     3 |   println(Coin{})
       |           ~~~~~~
     4 | }
+vlib/v/checker/tests/import_symbol_type_err.vv:3:11: error: unknown struct: crypto.Coin
+    1 | import crypto { Coin }
+    2 | fn main() {
+    3 |   println(Coin{})
+      |           ~~~~~~
+    4 | }
+vlib/v/checker/tests/import_symbol_type_err.vv:3:3: error: `println` can not print void expressions
+    1 | import crypto { Coin }
+    2 | fn main() {
+    3 |   println(Coin{})
+      |   ~~~~~~~~~~~~~~~
+    4 | }
diff --git a/vlib/v/checker/tests/incorrect_name_module.out b/vlib/v/checker/tests/incorrect_name_module.out
index 5e27858511..1ca2c466bd 100644
--- a/vlib/v/checker/tests/incorrect_name_module.out
+++ b/vlib/v/checker/tests/incorrect_name_module.out
@@ -8,3 +8,13 @@ vlib/v/checker/tests/incorrect_name_module.vv:1:1: error: module name `_A` canno
       | ~~~~~~~~~
     2 | 
     3 | import math as _
+vlib/v/checker/tests/incorrect_name_module.vv:1:1: error: module name `_A` cannot contain uppercase letters, use snake_case instead
+    1 | module _A
+      | ~~~~~~~~~
+    2 | 
+    3 | import math as _
+vlib/v/checker/tests/incorrect_name_module.vv:1:1: error: project must include a `main` module or be a shared library (compile with `v -shared`)
+    1 | module _A
+      | ^
+    2 | 
+    3 | import math as _
diff --git a/vlib/v/checker/tests/incorrect_smartcast2_err.out b/vlib/v/checker/tests/incorrect_smartcast2_err.out
index 804ff2fb11..aa269b2911 100644
--- a/vlib/v/checker/tests/incorrect_smartcast2_err.out
+++ b/vlib/v/checker/tests/incorrect_smartcast2_err.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/incorrect_smartcast2_err.vv:24:9: notice: smartcast can only be used on the ident or selector, e.g. match foo, match foo.bar
-   22 |
+   22 | 
    23 | fn doesntwork(v []Either[int, int]) {
    24 |     match v[0] {
       |            ~~~
@@ -12,3 +12,10 @@ vlib/v/checker/tests/incorrect_smartcast2_err.vv:26:17: error: field `error` doe
       |                          ~~~~~
    27 |         }
    28 |         else {}
+vlib/v/checker/tests/incorrect_smartcast2_err.vv:26:4: error: `println` can not print void expressions
+   24 |     match v[0] {
+   25 |         Left[int] {
+   26 |             println(v[0].error)
+      |             ~~~~~~~~~~~~~~~~~~~
+   27 |         }
+   28 |         else {}
diff --git a/vlib/v/checker/tests/incorrect_smartcast3_err.out b/vlib/v/checker/tests/incorrect_smartcast3_err.out
index 96a6471a1f..62e61a6366 100644
--- a/vlib/v/checker/tests/incorrect_smartcast3_err.out
+++ b/vlib/v/checker/tests/incorrect_smartcast3_err.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/incorrect_smartcast3_err.vv:25:5: notice: smartcasting requires either an immutable value, or an explicit mut keyword before the value
-   23 |
+   23 | 
    24 |     mut r := la.regex
    25 |     if r is RE {
       |        ^
@@ -7,7 +7,7 @@ vlib/v/checker/tests/incorrect_smartcast3_err.vv:25:5: notice: smartcasting requ
    27 |         println(r.matches_string(item))
 vlib/v/checker/tests/incorrect_smartcast3_err.vv:30:8: notice: smartcasting requires either an immutable value, or an explicit mut keyword before the value
    28 |     }
-   29 |
+   29 | 
    30 |     match r {
       |           ^
    31 |         RE { r.matches_string(item) }
@@ -19,8 +19,15 @@ vlib/v/checker/tests/incorrect_smartcast3_err.vv:27:13: error: unknown method or
       |                   ~~~~~~~~~~~~~~~~~~~~
    28 |     }
    29 |
-vlib/v/checker/tests/incorrect_smartcast3_err.vv:31:10: error: unknown method or field: `OurRegex.matches_string`
+vlib/v/checker/tests/incorrect_smartcast3_err.vv:27:3: error: `println` can not print void expressions
+   25 |     if r is RE {
+   26 |         println(r)
+   27 |         println(r.matches_string(item))
+      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+   28 |     }
    29 |
+vlib/v/checker/tests/incorrect_smartcast3_err.vv:31:10: error: unknown method or field: `OurRegex.matches_string`
+   29 | 
    30 |     match r {
    31 |         RE { r.matches_string(item) }
       |                ~~~~~~~~~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/incorrect_smartcast_err.out b/vlib/v/checker/tests/incorrect_smartcast_err.out
index 2f25c5cce6..8606a23831 100644
--- a/vlib/v/checker/tests/incorrect_smartcast_err.out
+++ b/vlib/v/checker/tests/incorrect_smartcast_err.out
@@ -19,3 +19,10 @@ vlib/v/checker/tests/incorrect_smartcast_err.vv:11:19: error: type `IExample` ha
       |                         ~~~~~
    12 |     }
    13 | }
+vlib/v/checker/tests/incorrect_smartcast_err.vv:11:3: error: `println` can not print void expressions
+    9 |     mut example := IExample(Example{field:"test"})
+   10 |     if example is Example{
+   11 |         println(example.field)
+      |         ~~~~~~~~~~~~~~~~~~~~~~
+   12 |     }
+   13 | }
diff --git a/vlib/v/checker/tests/index_expr.out b/vlib/v/checker/tests/index_expr.out
index 90aa0a21ea..7e65535952 100644
--- a/vlib/v/checker/tests/index_expr.out
+++ b/vlib/v/checker/tests/index_expr.out
@@ -67,3 +67,9 @@ vlib/v/checker/tests/index_expr.vv:20:8: error: negative index `-1`
    20 |     _ = a[-1..-2]
       |           ~~
    21 | }
+vlib/v/checker/tests/index_expr.vv:20:12: error: negative index `-2`
+   18 |     _ = a[-1..]
+   19 |     _ = a[..-1]
+   20 |     _ = a[-1..-2]
+      |               ~~
+   21 | }
diff --git a/vlib/v/checker/tests/index_invalid_call.out b/vlib/v/checker/tests/index_invalid_call.out
index 34f2f7b271..5a1a4971f0 100644
--- a/vlib/v/checker/tests/index_invalid_call.out
+++ b/vlib/v/checker/tests/index_invalid_call.out
@@ -5,9 +5,29 @@ vlib/v/checker/tests/index_invalid_call.vv:4:20: error: cannot call the value of
       |                       ^
     5 |     array := ["", "1"]
     6 |     array[0]()
+vlib/v/checker/tests/index_invalid_call.vv:4:20: error: unknown function: 
+    2 | fn main() {
+    3 |     m := map[string]string
+    4 |     eprintln(m['abc']())
+      |                       ^
+    5 |     array := ["", "1"]
+    6 |     array[0]()
+vlib/v/checker/tests/index_invalid_call.vv:4:2: error: `eprintln` can not print void expressions
+    2 | fn main() {
+    3 |     m := map[string]string
+    4 |     eprintln(m['abc']())
+      |     ~~~~~~~~~~~~~~~~~~~~
+    5 |     array := ["", "1"]
+    6 |     array[0]()
 vlib/v/checker/tests/index_invalid_call.vv:6:11: error: cannot call the element of the array, it is not a function
     4 |     eprintln(m['abc']())
     5 |     array := ["", "1"]
     6 |     array[0]()
       |              ^
     7 | }
+vlib/v/checker/tests/index_invalid_call.vv:6:11: error: unknown function: 
+    4 |     eprintln(m['abc']())
+    5 |     array := ["", "1"]
+    6 |     array[0]()
+      |              ^
+    7 | }
diff --git a/vlib/v/checker/tests/infix_compare_option_err.out b/vlib/v/checker/tests/infix_compare_option_err.out
index ecaa3f6ddc..64be235910 100644
--- a/vlib/v/checker/tests/infix_compare_option_err.out
+++ b/vlib/v/checker/tests/infix_compare_option_err.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/infix_compare_option_err.vv:6:5: error: unwrapped Option ca
       |        ~~~~~
     7 |     }
     8 | }
+vlib/v/checker/tests/infix_compare_option_err.vv:6:5: error: unwrapped Option cannot be used in an infix expression
+    4 | 
+    5 | fn main() {
+    6 |     if foo() > foo() {
+      |        ~~~~~
+    7 |     }
+    8 | }
diff --git a/vlib/v/checker/tests/infix_err.out b/vlib/v/checker/tests/infix_err.out
index 9e05ae3e44..d8a7183e34 100644
--- a/vlib/v/checker/tests/infix_err.out
+++ b/vlib/v/checker/tests/infix_err.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/infix_err.vv:7:5: error: mismatched types `string` and `?st
       |     ~~~~~~~~
     8 | _ = f() + ''
     9 | _ = f() + f()
+vlib/v/checker/tests/infix_err.vv:7:10: error: unwrapped Option cannot be used in an infix expression
+    5 |     return none
+    6 | }
+    7 | _ = '' + f()
+      |          ~~~
+    8 | _ = f() + ''
+    9 | _ = f() + f()
 vlib/v/checker/tests/infix_err.vv:8:5: error: mismatched types `?string` and `string`
     6 | }
     7 | _ = '' + f()
@@ -12,6 +19,13 @@ vlib/v/checker/tests/infix_err.vv:8:5: error: mismatched types `?string` and `st
       |     ~~~~~~~~
     9 | _ = f() + f()
    10 |
+vlib/v/checker/tests/infix_err.vv:8:5: error: unwrapped Option cannot be used in an infix expression
+    6 | }
+    7 | _ = '' + f()
+    8 | _ = f() + ''
+      |     ~~~
+    9 | _ = f() + f()
+   10 |
 vlib/v/checker/tests/infix_err.vv:9:9: error: `+` cannot be used with `?string`
     7 | _ = '' + f()
     8 | _ = f() + ''
@@ -19,6 +33,13 @@ vlib/v/checker/tests/infix_err.vv:9:9: error: `+` cannot be used with `?string`
       |         ^
    10 | 
    11 | _ = 4 + g()
+vlib/v/checker/tests/infix_err.vv:9:5: error: unwrapped Option cannot be used in an infix expression
+    7 | _ = '' + f()
+    8 | _ = f() + ''
+    9 | _ = f() + f()
+      |     ~~~
+   10 | 
+   11 | _ = 4 + g()
 vlib/v/checker/tests/infix_err.vv:11:7: error: `+` cannot be used with `?int`
     9 | _ = f() + f()
    10 | 
@@ -26,6 +47,13 @@ vlib/v/checker/tests/infix_err.vv:11:7: error: `+` cannot be used with `?int`
       |       ^
    12 | _ = int(0) + g() // FIXME not detected
    13 | _ = g() + int(3)
+vlib/v/checker/tests/infix_err.vv:11:9: error: unwrapped Option cannot be used in an infix expression
+    9 | _ = f() + f()
+   10 | 
+   11 | _ = 4 + g()
+      |         ~~~
+   12 | _ = int(0) + g() // FIXME not detected
+   13 | _ = g() + int(3)
 vlib/v/checker/tests/infix_err.vv:12:14: error: unwrapped Option cannot be used in an infix expression
    10 | 
    11 | _ = 4 + g()
@@ -40,6 +68,13 @@ vlib/v/checker/tests/infix_err.vv:13:9: error: `+` cannot be used with `?int`
       |         ^
    14 | _ = g() + 3
    15 |
+vlib/v/checker/tests/infix_err.vv:13:5: error: unwrapped Option cannot be used in an infix expression
+   11 | _ = 4 + g()
+   12 | _ = int(0) + g() // FIXME not detected
+   13 | _ = g() + int(3)
+      |     ~~~
+   14 | _ = g() + 3
+   15 |
 vlib/v/checker/tests/infix_err.vv:14:9: error: `+` cannot be used with `?int`
    12 | _ = int(0) + g() // FIXME not detected
    13 | _ = g() + int(3)
@@ -47,6 +82,13 @@ vlib/v/checker/tests/infix_err.vv:14:9: error: `+` cannot be used with `?int`
       |         ^
    15 | 
    16 | // binary operands
+vlib/v/checker/tests/infix_err.vv:14:5: error: unwrapped Option cannot be used in an infix expression
+   12 | _ = int(0) + g() // FIXME not detected
+   13 | _ = g() + int(3)
+   14 | _ = g() + 3
+      |     ~~~
+   15 | 
+   16 | // binary operands
 vlib/v/checker/tests/infix_err.vv:17:5: error: left operand for `&&` is not a boolean
    15 | 
    16 | // binary operands
@@ -54,6 +96,13 @@ vlib/v/checker/tests/infix_err.vv:17:5: error: left operand for `&&` is not a bo
       |     ^
    18 | _ = true || 2
    19 |
+vlib/v/checker/tests/infix_err.vv:17:10: error: right operand for `&&` is not a boolean
+   15 | 
+   16 | // binary operands
+   17 | _ = 1 && 2
+      |          ^
+   18 | _ = true || 2
+   19 |
 vlib/v/checker/tests/infix_err.vv:18:13: error: right operand for `||` is not a boolean
    16 | // binary operands
    17 | _ = 1 && 2
@@ -61,6 +110,13 @@ vlib/v/checker/tests/infix_err.vv:18:13: error: right operand for `||` is not a
       |             ^
    19 | 
    20 | // boolean expressions
+vlib/v/checker/tests/infix_err.vv:18:5: error: infix expr: cannot use `int literal` (right expression) as `bool`
+   16 | // binary operands
+   17 | _ = 1 && 2
+   18 | _ = true || 2
+      |     ~~~~~~~~~
+   19 | 
+   20 | // boolean expressions
 vlib/v/checker/tests/infix_err.vv:21:22: error: ambiguous boolean expression. use `()` to ensure correct order of operations
    19 | 
    20 | // boolean expressions
diff --git a/vlib/v/checker/tests/infix_is_notis_interface_unimplemented_err.out b/vlib/v/checker/tests/infix_is_notis_interface_unimplemented_err.out
index 950a38f8d2..42e629c15c 100644
--- a/vlib/v/checker/tests/infix_is_notis_interface_unimplemented_err.out
+++ b/vlib/v/checker/tests/infix_is_notis_interface_unimplemented_err.out
@@ -6,7 +6,7 @@ vlib/v/checker/tests/infix_is_notis_interface_unimplemented_err.vv:8:14: notice:
     9 |     }
    10 |
 vlib/v/checker/tests/infix_is_notis_interface_unimplemented_err.vv:12:14: notice: `int` doesn't implement method `msg` of interface `IError`. The usage of fields is being deprecated in favor of methods.
-   10 |
+   10 | 
    11 |     _ = f() or {
    12 |         _ = err is int
       |                    ~~~
@@ -20,7 +20,7 @@ vlib/v/checker/tests/infix_is_notis_interface_unimplemented_err.vv:8:14: error:
     9 |     }
    10 |
 vlib/v/checker/tests/infix_is_notis_interface_unimplemented_err.vv:12:14: error: `int` doesn't implement interface `IError`
-   10 |
+   10 | 
    11 |     _ = f() or {
    12 |         _ = err is int
       |                    ~~~
@@ -32,3 +32,9 @@ vlib/v/checker/tests/infix_is_notis_interface_unimplemented_err.vv:27:17: error:
    27 |     _ := ivalue is int
       |                    ~~~
    28 | }
+vlib/v/checker/tests/infix_is_notis_interface_unimplemented_err.vv:27:17: error: `int` doesn't implement interface `IAbc`
+   25 | fn type_unimplemented_interface() {
+   26 |     ivalue := IAbc(Struct{})
+   27 |     _ := ivalue is int
+      |                    ~~~
+   28 | }
diff --git a/vlib/v/checker/tests/interface_generic_err.out b/vlib/v/checker/tests/interface_generic_err.out
index bf888de203..697c3eabd0 100644
--- a/vlib/v/checker/tests/interface_generic_err.out
+++ b/vlib/v/checker/tests/interface_generic_err.out
@@ -4,7 +4,7 @@ vlib/v/checker/tests/interface_generic_err.vv:8:1: warning: unused variable: `wh
     8 | why := Why(what)
       | ~~~
 vlib/v/checker/tests/interface_generic_err.vv:7:9: error: could not infer generic type `T` in generic struct `What[T]`
-    5 |
+    5 | 
     6 | // no segfault without generic
     7 | what := What{}
       |         ~~~~~~
@@ -14,3 +14,8 @@ vlib/v/checker/tests/interface_generic_err.vv:8:8: error: could not infer generi
     7 | what := What{}
     8 | why := Why(what)
       |        ~~~~~~~~~
+vlib/v/checker/tests/interface_generic_err.vv:8:8: error: `What` does not implement interface `Why`, cannot cast `What` to interface `Why`
+    6 | // no segfault without generic
+    7 | what := What{}
+    8 | why := Why(what)
+      |        ~~~~~~~~~
diff --git a/vlib/v/checker/tests/invalid_multi_return_operations_err.out b/vlib/v/checker/tests/invalid_multi_return_operations_err.out
index 2406032379..7017ed9702 100644
--- a/vlib/v/checker/tests/invalid_multi_return_operations_err.out
+++ b/vlib/v/checker/tests/invalid_multi_return_operations_err.out
@@ -47,6 +47,20 @@ vlib/v/checker/tests/invalid_multi_return_operations_err.vv:11:9: error: invalid
       |         ~~~~~~~~~~~~~~
    12 | println(foo() >> foo())
    13 | println(foo() == foo())
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:11:9: error: invalid operation: shift on type `(int, int)`
+    9 | println(foo() % foo())
+   10 | println(foo() ^ foo())
+   11 | println(foo() << foo())
+      |         ~~~~~
+   12 | println(foo() >> foo())
+   13 | println(foo() == foo())
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:11:1: error: `println` can not print void expressions
+    9 | println(foo() % foo())
+   10 | println(foo() ^ foo())
+   11 | println(foo() << foo())
+      | ~~~~~~~~~~~~~~~~~~~~~~~
+   12 | println(foo() >> foo())
+   13 | println(foo() == foo())
 vlib/v/checker/tests/invalid_multi_return_operations_err.vv:12:9: error: invalid number of operand for `>>`. Only one allowed on each side.
    10 | println(foo() ^ foo())
    11 | println(foo() << foo())
@@ -54,6 +68,20 @@ vlib/v/checker/tests/invalid_multi_return_operations_err.vv:12:9: error: invalid
       |         ~~~~~~~~~~~~~~
    13 | println(foo() == foo())
    14 | println(foo() != foo())
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:12:9: error: invalid operation: shift on type `(int, int)`
+   10 | println(foo() ^ foo())
+   11 | println(foo() << foo())
+   12 | println(foo() >> foo())
+      |         ~~~~~
+   13 | println(foo() == foo())
+   14 | println(foo() != foo())
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:12:1: error: `println` can not print void expressions
+   10 | println(foo() ^ foo())
+   11 | println(foo() << foo())
+   12 | println(foo() >> foo())
+      | ~~~~~~~~~~~~~~~~~~~~~~~
+   13 | println(foo() == foo())
+   14 | println(foo() != foo())
 vlib/v/checker/tests/invalid_multi_return_operations_err.vv:13:9: error: invalid number of operand for `==`. Only one allowed on each side.
    11 | println(foo() << foo())
    12 | println(foo() >> foo())
@@ -103,6 +131,20 @@ vlib/v/checker/tests/invalid_multi_return_operations_err.vv:19:9: error: invalid
       |         ~~~~~~~~~~~~~~
    20 | println(foo() || foo())
    21 | println(foo() in foo())
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:19:9: error: left operand for `&&` is not a boolean
+   17 | println(foo() >= foo())
+   18 | println(foo() <= foo())
+   19 | println(foo() && foo())
+      |         ~~~~~
+   20 | println(foo() || foo())
+   21 | println(foo() in foo())
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:19:18: error: right operand for `&&` is not a boolean
+   17 | println(foo() >= foo())
+   18 | println(foo() <= foo())
+   19 | println(foo() && foo())
+      |                  ~~~~~
+   20 | println(foo() || foo())
+   21 | println(foo() in foo())
 vlib/v/checker/tests/invalid_multi_return_operations_err.vv:20:9: error: invalid number of operand for `||`. Only one allowed on each side.
    18 | println(foo() <= foo())
    19 | println(foo() && foo())
@@ -110,6 +152,20 @@ vlib/v/checker/tests/invalid_multi_return_operations_err.vv:20:9: error: invalid
       |         ~~~~~~~~~~~~~~
    21 | println(foo() in foo())
    22 | println(foo() !in foo())
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:20:9: error: left operand for `||` is not a boolean
+   18 | println(foo() <= foo())
+   19 | println(foo() && foo())
+   20 | println(foo() || foo())
+      |         ~~~~~
+   21 | println(foo() in foo())
+   22 | println(foo() !in foo())
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:20:18: error: right operand for `||` is not a boolean
+   18 | println(foo() <= foo())
+   19 | println(foo() && foo())
+   20 | println(foo() || foo())
+      |                  ~~~~~
+   21 | println(foo() in foo())
+   22 | println(foo() !in foo())
 vlib/v/checker/tests/invalid_multi_return_operations_err.vv:21:9: error: invalid number of operand for `in`. Only one allowed on each side.
    19 | println(foo() && foo())
    20 | println(foo() || foo())
@@ -117,6 +173,13 @@ vlib/v/checker/tests/invalid_multi_return_operations_err.vv:21:9: error: invalid
       |         ~~~~~~~~~~~~~~
    22 | println(foo() !in foo())
    23 | println(foo() <- foo())
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:21:15: error: `in` can only be used with arrays and maps
+   19 | println(foo() && foo())
+   20 | println(foo() || foo())
+   21 | println(foo() in foo())
+      |               ~~
+   22 | println(foo() !in foo())
+   23 | println(foo() <- foo())
 vlib/v/checker/tests/invalid_multi_return_operations_err.vv:22:9: error: invalid number of operand for `!in`. Only one allowed on each side.
    20 | println(foo() || foo())
    21 | println(foo() in foo())
@@ -124,6 +187,13 @@ vlib/v/checker/tests/invalid_multi_return_operations_err.vv:22:9: error: invalid
       |         ~~~~~~~~~~~~~~~
    23 | println(foo() <- foo())
    24 |
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:22:15: error: `!in` can only be used with arrays and maps
+   20 | println(foo() || foo())
+   21 | println(foo() in foo())
+   22 | println(foo() !in foo())
+      |               ~~~
+   23 | println(foo() <- foo())
+   24 |
 vlib/v/checker/tests/invalid_multi_return_operations_err.vv:23:9: error: invalid number of operand for `<-`. Only one allowed on each side.
    21 | println(foo() in foo())
    22 | println(foo() !in foo())
@@ -131,6 +201,20 @@ vlib/v/checker/tests/invalid_multi_return_operations_err.vv:23:9: error: invalid
       |         ~~~~~~~~~~~~~~
    24 | 
    25 | for _ in foo() .. foo() {
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:23:9: error: cannot push on non-channel `(int, int)`
+   21 | println(foo() in foo())
+   22 | println(foo() !in foo())
+   23 | println(foo() <- foo())
+      |         ~~~~~
+   24 | 
+   25 | for _ in foo() .. foo() {
+vlib/v/checker/tests/invalid_multi_return_operations_err.vv:23:1: error: `println` can not print void expressions
+   21 | println(foo() in foo())
+   22 | println(foo() !in foo())
+   23 | println(foo() <- foo())
+      | ~~~~~~~~~~~~~~~~~~~~~~~
+   24 | 
+   25 | for _ in foo() .. foo() {
 vlib/v/checker/tests/invalid_multi_return_operations_err.vv:25:10: error: multi-returns cannot be used in ranges. A range is from a single value to a single higher value.
    23 | println(foo() <- foo())
    24 | 
diff --git a/vlib/v/checker/tests/invalid_none_operations_err.out b/vlib/v/checker/tests/invalid_none_operations_err.out
index c45bd9b738..0279f9338c 100644
--- a/vlib/v/checker/tests/invalid_none_operations_err.out
+++ b/vlib/v/checker/tests/invalid_none_operations_err.out
@@ -44,6 +44,20 @@ vlib/v/checker/tests/invalid_none_operations_err.vv:7:9: error: invalid operator
       |         ~~~~~~~~~~~~
     8 | println(none >> none)
     9 | println(none == none)
+vlib/v/checker/tests/invalid_none_operations_err.vv:7:9: error: invalid operation: shift on type `none`
+    5 | println(none % none)
+    6 | println(none ^ none)
+    7 | println(none << none)
+      |         ~~~~
+    8 | println(none >> none)
+    9 | println(none == none)
+vlib/v/checker/tests/invalid_none_operations_err.vv:7:1: error: `println` can not print void expressions
+    5 | println(none % none)
+    6 | println(none ^ none)
+    7 | println(none << none)
+      | ~~~~~~~~~~~~~~~~~~~~~
+    8 | println(none >> none)
+    9 | println(none == none)
 vlib/v/checker/tests/invalid_none_operations_err.vv:8:9: error: invalid operator `>>` to `none` and `none`
     6 | println(none ^ none)
     7 | println(none << none)
@@ -51,6 +65,20 @@ vlib/v/checker/tests/invalid_none_operations_err.vv:8:9: error: invalid operator
       |         ~~~~~~~~~~~~
     9 | println(none == none)
    10 | println(none != none)
+vlib/v/checker/tests/invalid_none_operations_err.vv:8:9: error: invalid operation: shift on type `none`
+    6 | println(none ^ none)
+    7 | println(none << none)
+    8 | println(none >> none)
+      |         ~~~~
+    9 | println(none == none)
+   10 | println(none != none)
+vlib/v/checker/tests/invalid_none_operations_err.vv:8:1: error: `println` can not print void expressions
+    6 | println(none ^ none)
+    7 | println(none << none)
+    8 | println(none >> none)
+      | ~~~~~~~~~~~~~~~~~~~~~
+    9 | println(none == none)
+   10 | println(none != none)
 vlib/v/checker/tests/invalid_none_operations_err.vv:9:9: error: invalid operator `==` to `none` and `none`
     7 | println(none << none)
     8 | println(none >> none)
@@ -100,6 +128,20 @@ vlib/v/checker/tests/invalid_none_operations_err.vv:15:9: error: invalid operato
       |         ~~~~~~~~~~~~
    16 | println(none || none)
    17 | println(none is none)
+vlib/v/checker/tests/invalid_none_operations_err.vv:15:9: error: left operand for `&&` is not a boolean
+   13 | println(none >= none)
+   14 | println(none <= none)
+   15 | println(none && none)
+      |         ~~~~
+   16 | println(none || none)
+   17 | println(none is none)
+vlib/v/checker/tests/invalid_none_operations_err.vv:15:17: error: right operand for `&&` is not a boolean
+   13 | println(none >= none)
+   14 | println(none <= none)
+   15 | println(none && none)
+      |                 ~~~~
+   16 | println(none || none)
+   17 | println(none is none)
 vlib/v/checker/tests/invalid_none_operations_err.vv:16:9: error: invalid operator `||` to `none` and `none`
    14 | println(none <= none)
    15 | println(none && none)
@@ -107,6 +149,20 @@ vlib/v/checker/tests/invalid_none_operations_err.vv:16:9: error: invalid operato
       |         ~~~~~~~~~~~~
    17 | println(none is none)
    18 | println(none !is none)
+vlib/v/checker/tests/invalid_none_operations_err.vv:16:9: error: left operand for `||` is not a boolean
+   14 | println(none <= none)
+   15 | println(none && none)
+   16 | println(none || none)
+      |         ~~~~
+   17 | println(none is none)
+   18 | println(none !is none)
+vlib/v/checker/tests/invalid_none_operations_err.vv:16:17: error: right operand for `||` is not a boolean
+   14 | println(none <= none)
+   15 | println(none && none)
+   16 | println(none || none)
+      |                 ~~~~
+   17 | println(none is none)
+   18 | println(none !is none)
 vlib/v/checker/tests/invalid_none_operations_err.vv:17:9: error: invalid operator `is` to `none` and `none`
    15 | println(none && none)
    16 | println(none || none)
@@ -114,6 +170,13 @@ vlib/v/checker/tests/invalid_none_operations_err.vv:17:9: error: invalid operato
       |         ~~~~~~~~~~~~
    18 | println(none !is none)
    19 | println(none in none)
+vlib/v/checker/tests/invalid_none_operations_err.vv:17:14: error: `is` can only be used with interfaces and sum types
+   15 | println(none && none)
+   16 | println(none || none)
+   17 | println(none is none)
+      |              ~~
+   18 | println(none !is none)
+   19 | println(none in none)
 vlib/v/checker/tests/invalid_none_operations_err.vv:18:9: error: invalid operator `!is` to `none` and `none`
    16 | println(none || none)
    17 | println(none is none)
@@ -121,6 +184,13 @@ vlib/v/checker/tests/invalid_none_operations_err.vv:18:9: error: invalid operato
       |         ~~~~~~~~~~~~~
    19 | println(none in none)
    20 | println(none !in none)
+vlib/v/checker/tests/invalid_none_operations_err.vv:18:14: error: `!is` can only be used with interfaces and sum types
+   16 | println(none || none)
+   17 | println(none is none)
+   18 | println(none !is none)
+      |              ~~~
+   19 | println(none in none)
+   20 | println(none !in none)
 vlib/v/checker/tests/invalid_none_operations_err.vv:19:9: error: invalid operator `in` to `none` and `none`
    17 | println(none is none)
    18 | println(none !is none)
@@ -128,6 +198,13 @@ vlib/v/checker/tests/invalid_none_operations_err.vv:19:9: error: invalid operato
       |         ~~~~~~~~~~~~
    20 | println(none !in none)
    21 | println(none <- none)
+vlib/v/checker/tests/invalid_none_operations_err.vv:19:14: error: `in` can only be used with arrays and maps
+   17 | println(none is none)
+   18 | println(none !is none)
+   19 | println(none in none)
+      |              ~~
+   20 | println(none !in none)
+   21 | println(none <- none)
 vlib/v/checker/tests/invalid_none_operations_err.vv:20:9: error: invalid operator `!in` to `none` and `none`
    18 | println(none !is none)
    19 | println(none in none)
@@ -135,6 +212,13 @@ vlib/v/checker/tests/invalid_none_operations_err.vv:20:9: error: invalid operato
       |         ~~~~~~~~~~~~~
    21 | println(none <- none)
    22 |
+vlib/v/checker/tests/invalid_none_operations_err.vv:20:14: error: `!in` can only be used with arrays and maps
+   18 | println(none !is none)
+   19 | println(none in none)
+   20 | println(none !in none)
+      |              ~~~
+   21 | println(none <- none)
+   22 |
 vlib/v/checker/tests/invalid_none_operations_err.vv:21:9: error: invalid operator `<-` to `none` and `none`
    19 | println(none in none)
    20 | println(none !in none)
@@ -142,6 +226,20 @@ vlib/v/checker/tests/invalid_none_operations_err.vv:21:9: error: invalid operato
       |         ~~~~~~~~~~~~
    22 | 
    23 | for _ in none .. none {
+vlib/v/checker/tests/invalid_none_operations_err.vv:21:9: error: cannot push on non-channel `none`
+   19 | println(none in none)
+   20 | println(none !in none)
+   21 | println(none <- none)
+      |         ~~~~
+   22 | 
+   23 | for _ in none .. none {
+vlib/v/checker/tests/invalid_none_operations_err.vv:21:1: error: `println` can not print void expressions
+   19 | println(none in none)
+   20 | println(none !in none)
+   21 | println(none <- none)
+      | ~~~~~~~~~~~~~~~~~~~~~
+   22 | 
+   23 | for _ in none .. none {
 vlib/v/checker/tests/invalid_none_operations_err.vv:23:10: error: range type can not be none
    21 | println(none <- none)
    22 | 
diff --git a/vlib/v/checker/tests/invalid_property.out b/vlib/v/checker/tests/invalid_property.out
index e7839a42b9..127e9ef4d4 100644
--- a/vlib/v/checker/tests/invalid_property.out
+++ b/vlib/v/checker/tests/invalid_property.out
@@ -4,6 +4,12 @@ vlib/v/checker/tests/invalid_property.vv:2:7: error: `string` has no property `l
       |       ~~~~~~
     3 | _ = [1,2].foo
     4 |
+vlib/v/checker/tests/invalid_property.vv:2:3: error: assignment mismatch: 1 variable(s) 0 value(s)
+    1 | s :=''
+    2 | _ = s.length
+      |   ^
+    3 | _ = [1,2].foo
+    4 |
 vlib/v/checker/tests/invalid_property.vv:3:11: error: `[]int` has no property `foo`
     1 | s :=''
     2 | _ = s.length
@@ -11,8 +17,20 @@ vlib/v/checker/tests/invalid_property.vv:3:11: error: `[]int` has no property `f
       |           ~~~
     4 | 
     5 | mut fa := [3,4]!
+vlib/v/checker/tests/invalid_property.vv:3:3: error: assignment mismatch: 1 variable(s) 0 value(s)
+    1 | s :=''
+    2 | _ = s.length
+    3 | _ = [1,2].foo
+      |   ^
+    4 | 
+    5 | mut fa := [3,4]!
 vlib/v/checker/tests/invalid_property.vv:6:8: error: `[2]int` has no property `bar`
     4 | 
     5 | mut fa := [3,4]!
     6 | _ = fa.bar
       |        ~~~
+vlib/v/checker/tests/invalid_property.vv:6:3: error: assignment mismatch: 1 variable(s) 0 value(s)
+    4 | 
+    5 | mut fa := [3,4]!
+    6 | _ = fa.bar
+      |   ^
diff --git a/vlib/v/checker/tests/invalid_variable_err.out b/vlib/v/checker/tests/invalid_variable_err.out
index 42aa07c6ef..20bdfd2e9b 100644
--- a/vlib/v/checker/tests/invalid_variable_err.out
+++ b/vlib/v/checker/tests/invalid_variable_err.out
@@ -17,3 +17,10 @@ vlib/v/checker/tests/invalid_variable_err.vv:3:5: error: invalid variable `a`
       |        ^
     4 |     }
     5 | }
+vlib/v/checker/tests/invalid_variable_err.vv:3:5: error: non-bool type `void` used as if condition
+    1 | fn main() {
+    2 |     a, b := c
+    3 |     if a {
+      |        ^
+    4 |     }
+    5 | }
diff --git a/vlib/v/checker/tests/is_type_invalid.out b/vlib/v/checker/tests/is_type_invalid.out
index b410205631..1925738b1c 100644
--- a/vlib/v/checker/tests/is_type_invalid.out
+++ b/vlib/v/checker/tests/is_type_invalid.out
@@ -12,3 +12,10 @@ vlib/v/checker/tests/is_type_invalid.vv:18:10: error: `Cat` doesn't implement me
       |             ~~~
    19 |         println('not cool either')
    20 |     }
+vlib/v/checker/tests/is_type_invalid.vv:18:10: error: `Cat` doesn't implement interface `Animal`
+   16 |     }
+   17 |     a := Animal(Dog{})
+   18 |     if a is Cat {
+      |             ~~~
+   19 |         println('not cool either')
+   20 |     }
diff --git a/vlib/v/checker/tests/is_type_not_exist.out b/vlib/v/checker/tests/is_type_not_exist.out
index 1c52d7ac11..3803649e8f 100644
--- a/vlib/v/checker/tests/is_type_not_exist.out
+++ b/vlib/v/checker/tests/is_type_not_exist.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/is_type_not_exist.vv:8:10: error: is: type `SomethingThatDo
       |             ~~~~~~~~~~~~~~~~~~~~~~
     9 |         println('It should fail !')
    10 |     }
+vlib/v/checker/tests/is_type_not_exist.vv:8:10: error: `Integer` has no variant `SomethingThatDontExist`
+    6 | 
+    7 | fn fn_with_sum_type_param(i Integer) {
+    8 |     if i is SomethingThatDontExist {
+      |             ~~~~~~~~~~~~~~~~~~~~~~
+    9 |         println('It should fail !')
+   10 |     }
diff --git a/vlib/v/checker/tests/json_decode.out b/vlib/v/checker/tests/json_decode.out
index b0787f1fd9..4d7b569a26 100644
--- a/vlib/v/checker/tests/json_decode.out
+++ b/vlib/v/checker/tests/json_decode.out
@@ -12,6 +12,13 @@ vlib/v/checker/tests/json_decode.vv:12:7: error: json.decode expects 2 arguments
       |          ~~~~~~~~~~
    13 |     json.decode(string, '""')! // BAD
    14 |     json.decode(Num, '5')! // BAD
+vlib/v/checker/tests/json_decode.vv:12:17: error: unexpected `!`, the function `json.decode` does not return a Result
+   10 |     json.decode(St, '{a: ""}')! // OK
+   11 |     json.decode(St2, '{a: ""}')! // BAD
+   12 |     json.decode(St)! // BAD
+      |                    ^
+   13 |     json.decode(string, '""')! // BAD
+   14 |     json.decode(Num, '5')! // BAD
 vlib/v/checker/tests/json_decode.vv:13:14: error: json.decode: expected sum type, struct, map or array, found string
    11 |     json.decode(St2, '{a: ""}')! // BAD
    12 |     json.decode(St)! // BAD
diff --git a/vlib/v/checker/tests/json_decode_shared_err.out b/vlib/v/checker/tests/json_decode_shared_err.out
index 0295cc9b7c..cafbf9a346 100644
--- a/vlib/v/checker/tests/json_decode_shared_err.out
+++ b/vlib/v/checker/tests/json_decode_shared_err.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/json_decode_shared_err.vv:6:16: error: json.encode cannot h
       |                      ~~~~~~~~~~~~
     7 |     }
     8 | }
+vlib/v/checker/tests/json_decode_shared_err.vv:6:3: error: `println` can not print void expressions
+    4 |     shared data := [1, 2, 3]
+    5 |     rlock data {
+    6 |         println(json.encode(data))
+      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~
+    7 |     }
+    8 | }
diff --git a/vlib/v/checker/tests/lambda_expression_in_map.out b/vlib/v/checker/tests/lambda_expression_in_map.out
index e2c46e734d..f9d567329d 100644
--- a/vlib/v/checker/tests/lambda_expression_in_map.out
+++ b/vlib/v/checker/tests/lambda_expression_in_map.out
@@ -5,8 +5,20 @@ vlib/v/checker/tests/lambda_expression_in_map.vv:3:12: error: lambda expressions
       |            ~~
     4 | dump(a.map(|x| 5 * x))
     5 | dump(a.map(|x| x))
+vlib/v/checker/tests/lambda_expression_in_map.vv:3:8: error: dump expression can not be void
+    1 | a := [4, 5]
+    2 | dump(a.map(it))
+    3 | dump(a.map(|| 5))
+      |        ~~~~~~~~~
+    4 | dump(a.map(|x| 5 * x))
+    5 | dump(a.map(|x| x))
 vlib/v/checker/tests/lambda_expression_in_map.vv:6:12: error: lambda expressions used in the builtin array methods require exactly 1 parameter
     4 | dump(a.map(|x| 5 * x))
     5 | dump(a.map(|x| x))
     6 | dump(a.map(|x, y| x))
       |            ^
+vlib/v/checker/tests/lambda_expression_in_map.vv:6:8: error: dump expression can not be void
+    4 | dump(a.map(|x| 5 * x))
+    5 | dump(a.map(|x| x))
+    6 | dump(a.map(|x, y| x))
+      |        ~~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/like_operator_with_non_string_type_error.out b/vlib/v/checker/tests/like_operator_with_non_string_type_error.out
index 7561d1b6d5..bbcd4725c4 100644
--- a/vlib/v/checker/tests/like_operator_with_non_string_type_error.out
+++ b/vlib/v/checker/tests/like_operator_with_non_string_type_error.out
@@ -12,3 +12,17 @@ vlib/v/checker/tests/like_operator_with_non_string_type_error.vv:16:26: error: t
       |                                ~~
    17 |     }!)
    18 | }
+vlib/v/checker/tests/like_operator_with_non_string_type_error.vv:16:34: error: the right operand of the `like` operator must be a string type
+   14 | 
+   15 |     println(sql db {
+   16 |         select from User where 10 like true
+      |                                        ~~~~
+   17 |     }!)
+   18 | }
+vlib/v/checker/tests/like_operator_with_non_string_type_error.vv:16:26: error: V ORM: left side of the `like` expression must be one of the `User`'s fields
+   14 | 
+   15 |     println(sql db {
+   16 |         select from User where 10 like true
+      |                                ~~
+   17 |     }!)
+   18 | }
diff --git a/vlib/v/checker/tests/lock_already_locked.out b/vlib/v/checker/tests/lock_already_locked.out
index ae6152c3dd..68a3fbb654 100644
--- a/vlib/v/checker/tests/lock_already_locked.out
+++ b/vlib/v/checker/tests/lock_already_locked.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/lock_already_locked.vv:11:3: error: nested `lock`/`rlock` n
       |         ~~~~~
    12 |             a.x++
    13 |         }
+vlib/v/checker/tests/lock_already_locked.vv:11:9: error: `a` is already locked
+    9 |     }
+   10 |     lock a {
+   11 |         rlock a {
+      |               ^
+   12 |             a.x++
+   13 |         }
 vlib/v/checker/tests/lock_already_locked.vv:12:4: error: a has an `rlock` but needs a `lock`
    10 |     lock a {
    11 |         rlock a {
@@ -12,6 +19,13 @@ vlib/v/checker/tests/lock_already_locked.vv:12:4: error: a has an `rlock` but ne
       |             ^
    13 |         }
    14 |     }
+vlib/v/checker/tests/lock_already_locked.vv:12:4: error: `a` is `shared` and needs explicit lock for `v.ast.SelectorExpr`
+   10 |     lock a {
+   11 |         rlock a {
+   12 |             a.x++
+      |             ^
+   13 |         }
+   14 |     }
 vlib/v/checker/tests/lock_already_locked.vv:15:10: error: `a` is `shared` and must be `rlock`ed or `lock`ed to be used as non-mut argument to print
    13 |         }
    14 |     }
diff --git a/vlib/v/checker/tests/lock_already_rlocked.out b/vlib/v/checker/tests/lock_already_rlocked.out
index b7e3fdabc5..a489ad28f5 100644
--- a/vlib/v/checker/tests/lock_already_rlocked.out
+++ b/vlib/v/checker/tests/lock_already_rlocked.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/lock_already_rlocked.vv:11:3: error: nested `lock`/`rlock`
       |         ~~~~
    12 |             a.x++
    13 |         }
+vlib/v/checker/tests/lock_already_rlocked.vv:11:8: error: `a` is already read-locked
+    9 |     }
+   10 |     rlock a {
+   11 |         lock a {
+      |              ^
+   12 |             a.x++
+   13 |         }
 vlib/v/checker/tests/lock_already_rlocked.vv:15:10: error: `a` is `shared` and must be `rlock`ed or `lock`ed to be used as non-mut argument to print
    13 |         }
    14 |     }
diff --git a/vlib/v/checker/tests/map_delete.out b/vlib/v/checker/tests/map_delete.out
index ecfbca0e21..7706f321ff 100644
--- a/vlib/v/checker/tests/map_delete.out
+++ b/vlib/v/checker/tests/map_delete.out
@@ -12,6 +12,13 @@ vlib/v/checker/tests/map_delete.vv:6:4: error: expected 1 argument, but got 2
       |       ~~~~~~~~~~~~
     7 |     m2 := {
     8 |         '1': 1
+vlib/v/checker/tests/map_delete.vv:6:11: error: cannot use `int literal` as `string` in argument 1 to `Map.delete`
+    4 |     }
+    5 |     m.delete(1)
+    6 |     m.delete(1, 2)
+      |              ^
+    7 |     m2 := {
+    8 |         '1': 1
 vlib/v/checker/tests/map_delete.vv:10:2: error: `m2` is immutable, declare it with `mut` to make it mutable
     8 |         '1': 1
     9 |     }
diff --git a/vlib/v/checker/tests/map_ops.out b/vlib/v/checker/tests/map_ops.out
index d30508bfd7..6738739df1 100644
--- a/vlib/v/checker/tests/map_ops.out
+++ b/vlib/v/checker/tests/map_ops.out
@@ -12,9 +12,28 @@ vlib/v/checker/tests/map_ops.vv:4:3: error: invalid key: expected `int`, not `st
       |      ~~~~~~
     5 |     m[&m] += 4
     6 | }
+vlib/v/checker/tests/map_ops.vv:4:12: error: cannot assign to `m['hi']`: expected `string`, not `int literal`
+    2 |     mut m := map[int]string
+    3 |     _ = m[`!`]
+    4 |     m['hi'] = 8
+      |               ^
+    5 |     m[&m] += 4
+    6 | }
 vlib/v/checker/tests/map_ops.vv:5:3: error: invalid key: expected `int`, not `&map[int]string`
     3 |     _ = m[`!`]
     4 |     m['hi'] = 8
     5 |     m[&m] += 4
       |      ~~~~
     6 | }
+vlib/v/checker/tests/map_ops.vv:5:11: error: invalid right operand: string += int literal
+    3 |     _ = m[`!`]
+    4 |     m['hi'] = 8
+    5 |     m[&m] += 4
+      |              ^
+    6 | }
+vlib/v/checker/tests/map_ops.vv:5:11: error: cannot assign to `m[&m]`: expected `string`, not `int literal`
+    3 |     _ = m[`!`]
+    4 |     m['hi'] = 8
+    5 |     m[&m] += 4
+      |              ^
+    6 | }
diff --git a/vlib/v/checker/tests/match_expr_else.out b/vlib/v/checker/tests/match_expr_else.out
index cf708333d1..e6bb91dea2 100644
--- a/vlib/v/checker/tests/match_expr_else.out
+++ b/vlib/v/checker/tests/match_expr_else.out
@@ -19,3 +19,10 @@ vlib/v/checker/tests/match_expr_else.vv:34:3: error: `else` must be the last bra
       |         ~~~~
    35 |             'else'
    36 |         }
+vlib/v/checker/tests/match_expr_else.vv:34:3: error: match expression is exhaustive, `else` is unnecessary
+   32 |             'string'
+   33 |         }
+   34 |         else {
+      |         ~~~~
+   35 |             'else'
+   36 |         }
diff --git a/vlib/v/checker/tests/match_sumtype_multiple_types.out b/vlib/v/checker/tests/match_sumtype_multiple_types.out
index 9f2201f41f..a156c11e17 100644
--- a/vlib/v/checker/tests/match_sumtype_multiple_types.out
+++ b/vlib/v/checker/tests/match_sumtype_multiple_types.out
@@ -5,10 +5,24 @@ vlib/v/checker/tests/match_sumtype_multiple_types.vv:26:13: error: type `Charlie
       |                      ~~~~
    27 |             assert l.letter() == 'a'
    28 |         }
+vlib/v/checker/tests/match_sumtype_multiple_types.vv:26:11: error: assert can be used only with `bool` expressions, but found `void` instead
+   24 |     match l {
+   25 |         Alfa, Charlie {
+   26 |             assert l.char == `a`
+      |                    ~~~~~~~~~~~~~
+   27 |             assert l.letter() == 'a'
+   28 |         }
 vlib/v/checker/tests/match_sumtype_multiple_types.vv:27:13: error: unknown method: `Charlie.letter`
    25 |         Alfa, Charlie {
    26 |             assert l.char == `a`
    27 |             assert l.letter() == 'a'
       |                      ~~~~~~~~
    28 |         }
-   29 |         Bravo {
\ No newline at end of file
+   29 |         Bravo {
+vlib/v/checker/tests/match_sumtype_multiple_types.vv:27:11: error: assert can be used only with `bool` expressions, but found `void` instead
+   25 |         Alfa, Charlie {
+   26 |             assert l.char == `a`
+   27 |             assert l.letter() == 'a'
+      |                    ~~~~~~~~~~~~~~~~~
+   28 |         }
+   29 |         Bravo {
diff --git a/vlib/v/checker/tests/method_array_slice.out b/vlib/v/checker/tests/method_array_slice.out
index dde905525b..67b59f9709 100644
--- a/vlib/v/checker/tests/method_array_slice.out
+++ b/vlib/v/checker/tests/method_array_slice.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/method_array_slice.vv:5:12: error: .slice() is a private me
       |               ~~~~~~~~
     6 |     println(a[1..])
     7 | }
+vlib/v/checker/tests/method_array_slice.vv:5:2: error: `println` can not print void expressions
+    3 | fn main() {
+    4 |     a := os.args.clone()
+    5 |     println(a.slice(1))
+      |     ~~~~~~~~~~~~~~~~~~~
+    6 |     println(a[1..])
+    7 | }
diff --git a/vlib/v/checker/tests/method_call_with_empty_struct_init.out b/vlib/v/checker/tests/method_call_with_empty_struct_init.out
index c8d98ed7db..ea23669c83 100644
--- a/vlib/v/checker/tests/method_call_with_empty_struct_init.out
+++ b/vlib/v/checker/tests/method_call_with_empty_struct_init.out
@@ -4,3 +4,9 @@ vlib/v/checker/tests/method_call_with_empty_struct_init.vv:10:11: error: `{}` ca
    10 |     s.abc(0, {})
       |              ~~
    11 | }
+vlib/v/checker/tests/method_call_with_empty_struct_init.vv:10:11: error: `map{  }` (no value) used as value in argument 2 to `Abc.abc`
+    8 | fn main() {
+    9 |     s := Abc{}
+   10 |     s.abc(0, {})
+      |              ~~
+   11 | }
diff --git a/vlib/v/checker/tests/method_op_err.out b/vlib/v/checker/tests/method_op_err.out
index 547ceea909..c1ee67430d 100644
--- a/vlib/v/checker/tests/method_op_err.out
+++ b/vlib/v/checker/tests/method_op_err.out
@@ -47,6 +47,13 @@ vlib/v/checker/tests/method_op_err.vv:34:13: error: mismatched types `User` and
       |             ~~~~~~~~~~~~~~~~~~~~~~
    35 |     mut u := User{3, 4}
    36 |    _ = u
+vlib/v/checker/tests/method_op_err.vv:34:13: error: infix expr: cannot use `Foo` (right expression) as `User`
+   32 |     println(User{3, 4} - Foo{3, 3})
+   33 |     println(User{3, 2} < User{2, 4})
+   34 |     println(User{3, 4} < Foo{3, 4})
+      |             ~~~~~~~~~~~~~~~~~~~~~~
+   35 |     mut u := User{3, 4}
+   36 |    _ = u
 vlib/v/checker/tests/method_op_err.vv:37:10: error: cannot assign to `u`: expected `User`, not `int literal`
    35 |     mut u := User{3, 4}
    36 |    _ = u
@@ -61,6 +68,13 @@ vlib/v/checker/tests/method_op_err.vv:38:5: error: operator %= not defined on le
       |     ^
    39 |     u += User{2, 3}
    40 | }
+vlib/v/checker/tests/method_op_err.vv:38:7: error: undefined operation `User` % `User`
+   36 |    _ = u
+   37 |     u += 12
+   38 |     u %= User{1, 3}
+      |       ~~
+   39 |     u += User{2, 3}
+   40 | }
 vlib/v/checker/tests/method_op_err.vv:39:7: error: operator `+` must return `User` to be used as an assignment operator
    37 |     u += 12
    38 |     u %= User{1, 3}
diff --git a/vlib/v/checker/tests/minus_op_wrong_type_err.out b/vlib/v/checker/tests/minus_op_wrong_type_err.out
index 802d7aef8b..0caf3bc001 100644
--- a/vlib/v/checker/tests/minus_op_wrong_type_err.out
+++ b/vlib/v/checker/tests/minus_op_wrong_type_err.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/minus_op_wrong_type_err.vv:10:10: error: mismatched types `
       |             ~~~~~~~~~~
    11 |     println(10 - Aaa{})
    12 |     println([1, 2, 3] - 10)
+vlib/v/checker/tests/minus_op_wrong_type_err.vv:10:10: error: infix expr: cannot use `int literal` (right expression) as `Aaa`
+    8 | 
+    9 | fn main() {
+   10 |     println(Aaa{} - 10)
+      |             ~~~~~~~~~~
+   11 |     println(10 - Aaa{})
+   12 |     println([1, 2, 3] - 10)
 vlib/v/checker/tests/minus_op_wrong_type_err.vv:11:10: error: mismatched types `int literal` and `Aaa`
     9 | fn main() {
    10 |     println(Aaa{} - 10)
@@ -12,6 +19,13 @@ vlib/v/checker/tests/minus_op_wrong_type_err.vv:11:10: error: mismatched types `
       |             ~~~~~~~~~~
    12 |     println([1, 2, 3] - 10)
    13 |     println(10 - [1, 2, 3])
+vlib/v/checker/tests/minus_op_wrong_type_err.vv:11:10: error: infix expr: cannot use `Aaa` (right expression) as `int literal`
+    9 | fn main() {
+   10 |     println(Aaa{} - 10)
+   11 |     println(10 - Aaa{})
+      |             ~~~~~~~~~~
+   12 |     println([1, 2, 3] - 10)
+   13 |     println(10 - [1, 2, 3])
 vlib/v/checker/tests/minus_op_wrong_type_err.vv:12:10: error: mismatched types `[]int` and `int literal`
    10 |     println(Aaa{} - 10)
    11 |     println(10 - Aaa{})
@@ -19,6 +33,13 @@ vlib/v/checker/tests/minus_op_wrong_type_err.vv:12:10: error: mismatched types `
       |             ~~~~~~~~~~~~~~
    13 |     println(10 - [1, 2, 3])
    14 |     a := map[string]int{}
+vlib/v/checker/tests/minus_op_wrong_type_err.vv:12:10: error: infix expr: cannot use `int literal` (right expression) as `[]int`
+   10 |     println(Aaa{} - 10)
+   11 |     println(10 - Aaa{})
+   12 |     println([1, 2, 3] - 10)
+      |             ~~~~~~~~~~~~~~
+   13 |     println(10 - [1, 2, 3])
+   14 |     a := map[string]int{}
 vlib/v/checker/tests/minus_op_wrong_type_err.vv:13:10: error: mismatched types `int literal` and `[]int`
    11 |     println(10 - Aaa{})
    12 |     println([1, 2, 3] - 10)
@@ -26,6 +47,13 @@ vlib/v/checker/tests/minus_op_wrong_type_err.vv:13:10: error: mismatched types `
       |             ~~~~~~~~~~~~~~
    14 |     a := map[string]int{}
    15 |     println(a - 10)
+vlib/v/checker/tests/minus_op_wrong_type_err.vv:13:10: error: infix expr: cannot use `[]int` (right expression) as `int literal`
+   11 |     println(10 - Aaa{})
+   12 |     println([1, 2, 3] - 10)
+   13 |     println(10 - [1, 2, 3])
+      |             ~~~~~~~~~~~~~~
+   14 |     a := map[string]int{}
+   15 |     println(a - 10)
 vlib/v/checker/tests/minus_op_wrong_type_err.vv:15:10: error: mismatched types `map[string]int` and `int literal`
    13 |     println(10 - [1, 2, 3])
    14 |     a := map[string]int{}
@@ -33,6 +61,13 @@ vlib/v/checker/tests/minus_op_wrong_type_err.vv:15:10: error: mismatched types `
       |             ~~~~~~
    16 |     println(10 - a)
    17 |     println(-Aaa{})
+vlib/v/checker/tests/minus_op_wrong_type_err.vv:15:10: error: infix expr: cannot use `int literal` (right expression) as `map[string]int`
+   13 |     println(10 - [1, 2, 3])
+   14 |     a := map[string]int{}
+   15 |     println(a - 10)
+      |             ~~~~~~
+   16 |     println(10 - a)
+   17 |     println(-Aaa{})
 vlib/v/checker/tests/minus_op_wrong_type_err.vv:16:10: error: mismatched types `int literal` and `map[string]int`
    14 |     a := map[string]int{}
    15 |     println(a - 10)
@@ -40,6 +75,13 @@ vlib/v/checker/tests/minus_op_wrong_type_err.vv:16:10: error: mismatched types `
       |             ~~~~~~
    17 |     println(-Aaa{})
    18 |     println(-a)
+vlib/v/checker/tests/minus_op_wrong_type_err.vv:16:10: error: infix expr: cannot use `map[string]int` (right expression) as `int literal`
+   14 |     a := map[string]int{}
+   15 |     println(a - 10)
+   16 |     println(10 - a)
+      |             ~~~~~~
+   17 |     println(-Aaa{})
+   18 |     println(-a)
 vlib/v/checker/tests/minus_op_wrong_type_err.vv:17:10: error: operator `-` can only be used with numeric types, but the value after `-` is of type `Aaa` instead
    15 |     println(a - 10)
    16 |     println(10 - a)
diff --git a/vlib/v/checker/tests/mismatched_ptr_op_ptr.out b/vlib/v/checker/tests/mismatched_ptr_op_ptr.out
index a1a1d8af34..32324405fc 100644
--- a/vlib/v/checker/tests/mismatched_ptr_op_ptr.out
+++ b/vlib/v/checker/tests/mismatched_ptr_op_ptr.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/mismatched_ptr_op_ptr.vv:5:17: error: mismatched types `&st
       |                 ~~~
     6 |         println(b+b)
     7 |     }
+vlib/v/checker/tests/mismatched_ptr_op_ptr.vv:5:9: error: `println` can not print void expressions
+    3 |     unsafe {
+    4 |         b := &a
+    5 |         println(b+*b)
+      |         ~~~~~~~~~~~~~
+    6 |         println(b+b)
+    7 |     }
 vlib/v/checker/tests/mismatched_ptr_op_ptr.vv:6:17: error: invalid operator `+` to `&string` and `&string`
     4 |         b := &a
     5 |         println(b+*b)
diff --git a/vlib/v/checker/tests/misspelled_mod_const_should_have_suggestion.out b/vlib/v/checker/tests/misspelled_mod_const_should_have_suggestion.out
index ccd510a636..875ffb57cf 100644
--- a/vlib/v/checker/tests/misspelled_mod_const_should_have_suggestion.out
+++ b/vlib/v/checker/tests/misspelled_mod_const_should_have_suggestion.out
@@ -4,3 +4,8 @@ Did you mean `time.second`?
     2 | 
     3 | time.sleep(1 * time.secondz)
       |                     ~~~~~~~
+vlib/v/checker/tests/misspelled_mod_const_should_have_suggestion.vv:3:12: error: `1 * time.secondz` (no value) used as value in argument 1 to `time.sleep`
+    1 | import time
+    2 | 
+    3 | time.sleep(1 * time.secondz)
+      |            ~~~~~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/misspelled_mod_fn_name_should_have_suggestion.out b/vlib/v/checker/tests/misspelled_mod_fn_name_should_have_suggestion.out
index 8ff5208c5d..35f39d5966 100644
--- a/vlib/v/checker/tests/misspelled_mod_fn_name_should_have_suggestion.out
+++ b/vlib/v/checker/tests/misspelled_mod_fn_name_should_have_suggestion.out
@@ -4,3 +4,8 @@ Did you mean `os.read_file`?
     2 | 
     3 | dump(os.read_fil('abc'))
       |         ~~~~~~~~~~~~~~~
+vlib/v/checker/tests/misspelled_mod_fn_name_should_have_suggestion.vv:3:9: error: dump expression can not be void
+    1 | import os
+    2 | 
+    3 | dump(os.read_fil('abc'))
+      |         ~~~~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/mod_op_wrong_type_err.out b/vlib/v/checker/tests/mod_op_wrong_type_err.out
index 6ae53be6bd..1fb7974390 100644
--- a/vlib/v/checker/tests/mod_op_wrong_type_err.out
+++ b/vlib/v/checker/tests/mod_op_wrong_type_err.out
@@ -19,6 +19,13 @@ vlib/v/checker/tests/mod_op_wrong_type_err.vv:5:10: error: mismatched types `[]i
       |             ~~~~~~~~~~~
     6 |     println(1 % [1,2,3])
     7 |     a := Aaa{}
+vlib/v/checker/tests/mod_op_wrong_type_err.vv:5:10: error: infix expr: cannot use `int literal` (right expression) as `[]int`
+    3 |     println(0.5 % 1)
+    4 |     println(1 % 0.5)
+    5 |     println([1,2,3] % 1)
+      |             ~~~~~~~~~~~
+    6 |     println(1 % [1,2,3])
+    7 |     a := Aaa{}
 vlib/v/checker/tests/mod_op_wrong_type_err.vv:6:10: error: mismatched types `int literal` and `[]int`
     4 |     println(1 % 0.5)
     5 |     println([1,2,3] % 1)
@@ -26,6 +33,13 @@ vlib/v/checker/tests/mod_op_wrong_type_err.vv:6:10: error: mismatched types `int
       |             ~~~~~~~~~~~
     7 |     a := Aaa{}
     8 |     println(a % 1)
+vlib/v/checker/tests/mod_op_wrong_type_err.vv:6:10: error: infix expr: cannot use `[]int` (right expression) as `int literal`
+    4 |     println(1 % 0.5)
+    5 |     println([1,2,3] % 1)
+    6 |     println(1 % [1,2,3])
+      |             ~~~~~~~~~~~
+    7 |     a := Aaa{}
+    8 |     println(a % 1)
 vlib/v/checker/tests/mod_op_wrong_type_err.vv:8:10: error: mismatched types `Aaa` and `int literal`
     6 |     println(1 % [1,2,3])
     7 |     a := Aaa{}
@@ -33,6 +47,13 @@ vlib/v/checker/tests/mod_op_wrong_type_err.vv:8:10: error: mismatched types `Aaa
       |             ~~~~~
     9 |     println(1 % a)
    10 |     b := map[string]int
+vlib/v/checker/tests/mod_op_wrong_type_err.vv:8:10: error: infix expr: cannot use `int literal` (right expression) as `Aaa`
+    6 |     println(1 % [1,2,3])
+    7 |     a := Aaa{}
+    8 |     println(a % 1)
+      |             ~~~~~
+    9 |     println(1 % a)
+   10 |     b := map[string]int
 vlib/v/checker/tests/mod_op_wrong_type_err.vv:9:10: error: mismatched types `int literal` and `Aaa`
     7 |     a := Aaa{}
     8 |     println(a % 1)
@@ -40,6 +61,13 @@ vlib/v/checker/tests/mod_op_wrong_type_err.vv:9:10: error: mismatched types `int
       |             ~~~~~
    10 |     b := map[string]int
    11 |     println(b % 1)
+vlib/v/checker/tests/mod_op_wrong_type_err.vv:9:10: error: infix expr: cannot use `Aaa` (right expression) as `int literal`
+    7 |     a := Aaa{}
+    8 |     println(a % 1)
+    9 |     println(1 % a)
+      |             ~~~~~
+   10 |     b := map[string]int
+   11 |     println(b % 1)
 vlib/v/checker/tests/mod_op_wrong_type_err.vv:11:10: error: mismatched types `map[string]int` and `int literal`
     9 |     println(1 % a)
    10 |     b := map[string]int
@@ -47,10 +75,22 @@ vlib/v/checker/tests/mod_op_wrong_type_err.vv:11:10: error: mismatched types `ma
       |             ~~~~~
    12 |     println(1 % b)
    13 | }
+vlib/v/checker/tests/mod_op_wrong_type_err.vv:11:10: error: infix expr: cannot use `int literal` (right expression) as `map[string]int`
+    9 |     println(1 % a)
+   10 |     b := map[string]int
+   11 |     println(b % 1)
+      |             ~~~~~
+   12 |     println(1 % b)
+   13 | }
 vlib/v/checker/tests/mod_op_wrong_type_err.vv:12:10: error: mismatched types `int literal` and `map[string]int`
    10 |     b := map[string]int
    11 |     println(b % 1)
    12 |     println(1 % b)
       |             ~~~~~
    13 | }
-
+vlib/v/checker/tests/mod_op_wrong_type_err.vv:12:10: error: infix expr: cannot use `map[string]int` (right expression) as `int literal`
+   10 |     b := map[string]int
+   11 |     println(b % 1)
+   12 |     println(1 % b)
+      |             ~~~~~
+   13 | }
diff --git a/vlib/v/checker/tests/modules/deprecated_module.out b/vlib/v/checker/tests/modules/deprecated_module.out
index 1ccfee7c8f..87056136f2 100644
--- a/vlib/v/checker/tests/modules/deprecated_module.out
+++ b/vlib/v/checker/tests/modules/deprecated_module.out
@@ -11,3 +11,9 @@ vlib/v/checker/tests/modules/deprecated_module/main.v:16:11: error: undefined id
    16 |     dump(ttt.non_existing)
       |              ~~~~~~~~~~~~
    17 | }
+vlib/v/checker/tests/modules/deprecated_module/main.v:16:11: error: dump expression can not be void
+   14 |     dump(ttt.f())
+   15 |     dump(yyy.f())
+   16 |     dump(ttt.non_existing)
+      |              ~~~~~~~~~~~~
+   17 | }
diff --git a/vlib/v/checker/tests/mul_op_wrong_type_err.out b/vlib/v/checker/tests/mul_op_wrong_type_err.out
index 6bd5ff9ab7..10ca288dd8 100644
--- a/vlib/v/checker/tests/mul_op_wrong_type_err.out
+++ b/vlib/v/checker/tests/mul_op_wrong_type_err.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/mul_op_wrong_type_err.vv:5:13: error: mismatched types `Aaa
       |             ~~~~~~~~~~
     6 |     println(10 * Aaa{})
     7 |     println([1,2,3] * 10)
+vlib/v/checker/tests/mul_op_wrong_type_err.vv:5:13: error: infix expr: cannot use `int literal` (right expression) as `Aaa`
+    3 | struct Aaa{}
+    4 | fn main() {
+    5 |     println(Aaa{} * 10)
+      |             ~~~~~~~~~~
+    6 |     println(10 * Aaa{})
+    7 |     println([1,2,3] * 10)
 vlib/v/checker/tests/mul_op_wrong_type_err.vv:6:13: error: mismatched types `int literal` and `Aaa`
     4 | fn main() {
     5 |     println(Aaa{} * 10)
@@ -12,6 +19,13 @@ vlib/v/checker/tests/mul_op_wrong_type_err.vv:6:13: error: mismatched types `int
       |             ~~~~~~~~~~
     7 |     println([1,2,3] * 10)
     8 |     println(10 * [1,2,3])
+vlib/v/checker/tests/mul_op_wrong_type_err.vv:6:13: error: infix expr: cannot use `Aaa` (right expression) as `int literal`
+    4 | fn main() {
+    5 |     println(Aaa{} * 10)
+    6 |     println(10 * Aaa{})
+      |             ~~~~~~~~~~
+    7 |     println([1,2,3] * 10)
+    8 |     println(10 * [1,2,3])
 vlib/v/checker/tests/mul_op_wrong_type_err.vv:7:13: error: mismatched types `[]int` and `int literal`
     5 |     println(Aaa{} * 10)
     6 |     println(10 * Aaa{})
@@ -19,6 +33,13 @@ vlib/v/checker/tests/mul_op_wrong_type_err.vv:7:13: error: mismatched types `[]i
       |             ~~~~~~~~~~~~
     8 |     println(10 * [1,2,3])
     9 |     a := map[string]int
+vlib/v/checker/tests/mul_op_wrong_type_err.vv:7:13: error: infix expr: cannot use `int literal` (right expression) as `[]int`
+    5 |     println(Aaa{} * 10)
+    6 |     println(10 * Aaa{})
+    7 |     println([1,2,3] * 10)
+      |             ~~~~~~~~~~~~
+    8 |     println(10 * [1,2,3])
+    9 |     a := map[string]int
 vlib/v/checker/tests/mul_op_wrong_type_err.vv:8:13: error: mismatched types `int literal` and `[]int`
     6 |     println(10 * Aaa{})
     7 |     println([1,2,3] * 10)
@@ -26,6 +47,13 @@ vlib/v/checker/tests/mul_op_wrong_type_err.vv:8:13: error: mismatched types `int
       |             ~~~~~~~~~~~~
     9 |     a := map[string]int
    10 |     println(a * 10)
+vlib/v/checker/tests/mul_op_wrong_type_err.vv:8:13: error: infix expr: cannot use `[]int` (right expression) as `int literal`
+    6 |     println(10 * Aaa{})
+    7 |     println([1,2,3] * 10)
+    8 |     println(10 * [1,2,3])
+      |             ~~~~~~~~~~~~
+    9 |     a := map[string]int
+   10 |     println(a * 10)
 vlib/v/checker/tests/mul_op_wrong_type_err.vv:10:13: error: mismatched types `map[string]int` and `int literal`
     8 |     println(10 * [1,2,3])
     9 |     a := map[string]int
@@ -33,6 +61,13 @@ vlib/v/checker/tests/mul_op_wrong_type_err.vv:10:13: error: mismatched types `ma
       |             ~~~~~~
    11 |     println(10 * a)
    12 |     c1 := cmplx.complex(1,-2)
+vlib/v/checker/tests/mul_op_wrong_type_err.vv:10:13: error: infix expr: cannot use `int literal` (right expression) as `map[string]int`
+    8 |     println(10 * [1,2,3])
+    9 |     a := map[string]int
+   10 |     println(a * 10)
+      |             ~~~~~~
+   11 |     println(10 * a)
+   12 |     c1 := cmplx.complex(1,-2)
 vlib/v/checker/tests/mul_op_wrong_type_err.vv:11:13: error: mismatched types `int literal` and `map[string]int`
     9 |     a := map[string]int
    10 |     println(a * 10)
@@ -40,6 +75,13 @@ vlib/v/checker/tests/mul_op_wrong_type_err.vv:11:13: error: mismatched types `in
       |             ~~~~~~
    12 |     c1 := cmplx.complex(1,-2)
    13 |     c2 := c1 * 2.0
+vlib/v/checker/tests/mul_op_wrong_type_err.vv:11:13: error: infix expr: cannot use `map[string]int` (right expression) as `int literal`
+    9 |     a := map[string]int
+   10 |     println(a * 10)
+   11 |     println(10 * a)
+      |             ~~~~~~
+   12 |     c1 := cmplx.complex(1,-2)
+   13 |     c2 := c1 * 2.0
 vlib/v/checker/tests/mul_op_wrong_type_err.vv:13:8: error: infix expr: cannot use `float literal` (right expression) as `math.complex.Complex`
    11 |     println(10 * a)
    12 |     c1 := cmplx.complex(1,-2)
@@ -54,4 +96,3 @@ vlib/v/checker/tests/mul_op_wrong_type_err.vv:15:8: error: infix expr: cannot us
       |           ~~~~~~~~
    16 |     println(c3)
    17 | }
-
diff --git a/vlib/v/checker/tests/mut_arg.out b/vlib/v/checker/tests/mut_arg.out
index 253d73a9e8..5b7d277e37 100644
--- a/vlib/v/checker/tests/mut_arg.out
+++ b/vlib/v/checker/tests/mut_arg.out
@@ -19,6 +19,13 @@ vlib/v/checker/tests/mut_arg.vv:6:3: error: function `f` parameter `par` is `mut
       |   ~~~~~
     7 | mut a := [1,2]
     8 | f(a)
+vlib/v/checker/tests/mut_arg.vv:6:3: error: cannot use `[]int` as `&[]int` in argument 1 to `f`
+    4 | }
+    5 | 
+    6 | f([3,4])
+      |   ~~~~~
+    7 | mut a := [1,2]
+    8 | f(a)
 vlib/v/checker/tests/mut_arg.vv:8:3: error: function `f` parameter `par` is `mut`, so use `mut a` instead
     6 | f([3,4])
     7 | mut a := [1,2]
@@ -26,12 +33,31 @@ vlib/v/checker/tests/mut_arg.vv:8:3: error: function `f` parameter `par` is `mut
       |   ^
     9 | 
    10 | g(mut [3,4])
+vlib/v/checker/tests/mut_arg.vv:8:3: error: cannot use `[]int` as `&[]int` in argument 1 to `f`
+    6 | f([3,4])
+    7 | mut a := [1,2]
+    8 | f(a)
+      |   ^
+    9 | 
+   10 | g(mut [3,4])
 vlib/v/checker/tests/mut_arg.vv:10:7: error: array literal can not be modified
     8 | f(a)
     9 | 
    10 | g(mut [3,4])
       |       ~~~~~
    11 | g(mut a)
+vlib/v/checker/tests/mut_arg.vv:10:7: error: cannot pass expression as `mut`
+    8 | f(a)
+    9 | 
+   10 | g(mut [3,4])
+      |       ~~~~~
+   11 | g(mut a)
+vlib/v/checker/tests/mut_arg.vv:10:7: error: `g` parameter `par` is not `mut`, `mut` is not needed`
+    8 | f(a)
+    9 | 
+   10 | g(mut [3,4])
+      |       ~~~~~
+   11 | g(mut a)
 vlib/v/checker/tests/mut_arg.vv:11:7: error: `g` parameter `par` is not `mut`, `mut` is not needed`
     9 | 
    10 | g(mut [3,4])
diff --git a/vlib/v/checker/tests/nil.out b/vlib/v/checker/tests/nil.out
index cbe3f705da..58a774c3b7 100644
--- a/vlib/v/checker/tests/nil.out
+++ b/vlib/v/checker/tests/nil.out
@@ -4,3 +4,9 @@ vlib/v/checker/tests/nil.vv:2:11: error: `nil` is only allowed in `unsafe` code
       |              ~~~
     3 |     println(value)
     4 | }
+vlib/v/checker/tests/nil.vv:2:11: error: use of untyped nil in assignment (use `unsafe` | false)
+    1 | fn main() {
+    2 |     value := nil
+      |              ~~~
+    3 |     println(value)
+    4 | }
diff --git a/vlib/v/checker/tests/option_propagate_nested.out b/vlib/v/checker/tests/option_propagate_nested.out
index 2b3b006fdd..a690a20bef 100644
--- a/vlib/v/checker/tests/option_propagate_nested.out
+++ b/vlib/v/checker/tests/option_propagate_nested.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/option_propagate_nested.vv:10:18: error: to propagate the Option call, `xx_prop` must return an Option
-    8 |
+    8 | 
     9 | fn xx_prop() string {
    10 |     s := ret(raise()?)
       |                     ^
@@ -7,13 +7,27 @@ vlib/v/checker/tests/option_propagate_nested.vv:10:18: error: to propagate the O
    12 | }
 Details: vlib/v/checker/tests/option_propagate_nested.vv:9:14: details: prepend ? before the declaration of the return type of `xx_prop`
     7 | }
-    8 |
+    8 | 
+    9 | fn xx_prop() string {
+      |              ~~~~~~
+   10 |     s := ret(raise()?)
+   11 |     return s
+vlib/v/checker/tests/option_propagate_nested.vv:10:18: error: to propagate the call, `xx_prop` must return an Option type
+    8 | 
+    9 | fn xx_prop() string {
+   10 |     s := ret(raise()?)
+      |                     ^
+   11 |     return s
+   12 | }
+Details: vlib/v/checker/tests/option_propagate_nested.vv:9:14: details: prepend ? before the declaration of the return type of `xx_prop`
+    7 | }
+    8 | 
     9 | fn xx_prop() string {
       |              ~~~~~~
    10 |     s := ret(raise()?)
    11 |     return s
 vlib/v/checker/tests/option_propagate_nested.vv:28:21: error: to propagate the Result call, `aa_propagate` must return a Result
-   26 |
+   26 | 
    27 | fn (mut s St) aa_propagate() {
    28 |     f := retf(s.raise()!)
       |                        ^
@@ -21,7 +35,21 @@ vlib/v/checker/tests/option_propagate_nested.vv:28:21: error: to propagate the R
    30 |     println(f)
 Details: vlib/v/checker/tests/option_propagate_nested.vv:27:30: details: prepend ! before the declaration of the return type of `aa_propagate`
    25 | }
-   26 |
+   26 | 
+   27 | fn (mut s St) aa_propagate() {
+      |                              ^
+   28 |     f := retf(s.raise()!)
+   29 |     s.z = 7.5
+vlib/v/checker/tests/option_propagate_nested.vv:28:21: error: to propagate the call, `aa_propagate` must return a Result type
+   26 | 
+   27 | fn (mut s St) aa_propagate() {
+   28 |     f := retf(s.raise()!)
+      |                        ^
+   29 |     s.z = 7.5
+   30 |     println(f)
+Details: vlib/v/checker/tests/option_propagate_nested.vv:27:30: details: prepend ! before the declaration of the return type of `aa_propagate`
+   25 | }
+   26 | 
    27 | fn (mut s St) aa_propagate() {
       |                              ^
    28 |     f := retf(s.raise()!)
diff --git a/vlib/v/checker/tests/option_ptr_err.out b/vlib/v/checker/tests/option_ptr_err.out
index 5096b8d5e1..2c71fc0164 100644
--- a/vlib/v/checker/tests/option_ptr_err.out
+++ b/vlib/v/checker/tests/option_ptr_err.out
@@ -4,3 +4,9 @@ vlib/v/checker/tests/option_ptr_err.vv:3:10: error: type `?int` is an Option, it
     3 |     assert *var == 0
       |             ~~~
     4 | }
+vlib/v/checker/tests/option_ptr_err.vv:3:9: error: unwrapped Option cannot be used in an infix expression
+    1 | fn main() {
+    2 |     mut var := unsafe { ?&int(none) }
+    3 |     assert *var == 0
+      |            ^
+    4 | }
diff --git a/vlib/v/checker/tests/option_type_call_err.out b/vlib/v/checker/tests/option_type_call_err.out
index f789eeeec1..a785626bed 100644
--- a/vlib/v/checker/tests/option_type_call_err.out
+++ b/vlib/v/checker/tests/option_type_call_err.out
@@ -4,3 +4,15 @@ vlib/v/checker/tests/option_type_call_err.vv:4:5: error: os.ls() returns a Resul
     4 |     os.ls('.').filter(it.ends_with('.v')) or { return }
       |        ~~~~~~~
     5 | }
+vlib/v/checker/tests/option_type_call_err.vv:4:5: error: Result type cannot be called directly
+    2 | 
+    3 | fn main() {
+    4 |     os.ls('.').filter(it.ends_with('.v')) or { return }
+      |        ~~~~~~~
+    5 | }
+vlib/v/checker/tests/option_type_call_err.vv:4:40: error: unexpected `or` block, the function `filter` does not return an Option or a Result
+    2 | 
+    3 | fn main() {
+    4 |     os.ls('.').filter(it.ends_with('.v')) or { return }
+      |                                           ~~~~~~~~~~~~~
+    5 | }
diff --git a/vlib/v/checker/tests/option_var_unwrap_err.out b/vlib/v/checker/tests/option_var_unwrap_err.out
index 58d1887898..b2f416cbdf 100644
--- a/vlib/v/checker/tests/option_var_unwrap_err.out
+++ b/vlib/v/checker/tests/option_var_unwrap_err.out
@@ -12,3 +12,10 @@ Details: vlib/v/checker/tests/option_var_unwrap_err.vv:4:21: details: prepend ?
       |                     ~~~~~~
     5 |     return a?
     6 | }
+vlib/v/checker/tests/option_var_unwrap_err.vv:5:2: error: should not unwrap option var on return, it could be none
+    3 | 
+    4 | fn abc_2(a ?string) string {
+    5 |     return a?
+      |     ~~~~~~~~
+    6 | }
+    7 |
diff --git a/vlib/v/checker/tests/orm_db_expr_option_error.out b/vlib/v/checker/tests/orm_db_expr_option_error.out
index c04311c847..ea35c7edd1 100644
--- a/vlib/v/checker/tests/orm_db_expr_option_error.out
+++ b/vlib/v/checker/tests/orm_db_expr_option_error.out
@@ -12,6 +12,48 @@ vlib/v/checker/tests/orm_db_expr_option_error.vv:22:11: error: `Account` doesn't
       |              ~~~~~~~
    23 |         select from Account
    24 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:22:11: error: `Account` doesn't implement method `insert` of interface `orm.Connection`
+   20 |     account := Account{}
+   21 | 
+   22 |     _ := sql account {
+      |              ~~~~~~~
+   23 |         select from Account
+   24 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:22:11: error: `Account` doesn't implement method `update` of interface `orm.Connection`
+   20 |     account := Account{}
+   21 | 
+   22 |     _ := sql account {
+      |              ~~~~~~~
+   23 |         select from Account
+   24 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:22:11: error: `Account` doesn't implement method `delete` of interface `orm.Connection`
+   20 |     account := Account{}
+   21 | 
+   22 |     _ := sql account {
+      |              ~~~~~~~
+   23 |         select from Account
+   24 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:22:11: error: `Account` doesn't implement method `create` of interface `orm.Connection`
+   20 |     account := Account{}
+   21 | 
+   22 |     _ := sql account {
+      |              ~~~~~~~
+   23 |         select from Account
+   24 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:22:11: error: `Account` doesn't implement method `drop` of interface `orm.Connection`
+   20 |     account := Account{}
+   21 | 
+   22 |     _ := sql account {
+      |              ~~~~~~~
+   23 |         select from Account
+   24 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:22:11: error: `Account` doesn't implement method `last_id` of interface `orm.Connection`
+   20 |     account := Account{}
+   21 | 
+   22 |     _ := sql account {
+      |              ~~~~~~~
+   23 |         select from Account
+   24 |     }!
 vlib/v/checker/tests/orm_db_expr_option_error.vv:26:6: error: `Account` doesn't implement method `select` of interface `orm.Connection`
    24 |     }!
    25 | 
@@ -19,6 +61,48 @@ vlib/v/checker/tests/orm_db_expr_option_error.vv:26:6: error: `Account` doesn't
       |         ~~~~~~~
    27 |         insert account into Account
    28 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:26:6: error: `Account` doesn't implement method `insert` of interface `orm.Connection`
+   24 |     }!
+   25 | 
+   26 |     sql account {
+      |         ~~~~~~~
+   27 |         insert account into Account
+   28 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:26:6: error: `Account` doesn't implement method `update` of interface `orm.Connection`
+   24 |     }!
+   25 | 
+   26 |     sql account {
+      |         ~~~~~~~
+   27 |         insert account into Account
+   28 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:26:6: error: `Account` doesn't implement method `delete` of interface `orm.Connection`
+   24 |     }!
+   25 | 
+   26 |     sql account {
+      |         ~~~~~~~
+   27 |         insert account into Account
+   28 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:26:6: error: `Account` doesn't implement method `create` of interface `orm.Connection`
+   24 |     }!
+   25 | 
+   26 |     sql account {
+      |         ~~~~~~~
+   27 |         insert account into Account
+   28 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:26:6: error: `Account` doesn't implement method `drop` of interface `orm.Connection`
+   24 |     }!
+   25 | 
+   26 |     sql account {
+      |         ~~~~~~~
+   27 |         insert account into Account
+   28 |     }!
+vlib/v/checker/tests/orm_db_expr_option_error.vv:26:6: error: `Account` doesn't implement method `last_id` of interface `orm.Connection`
+   24 |     }!
+   25 | 
+   26 |     sql account {
+      |         ~~~~~~~
+   27 |         insert account into Account
+   28 |     }!
 vlib/v/checker/tests/orm_db_expr_option_error.vv:30:6: error: expected `sqlite.DB`, not `?sqlite.DB`
    28 |     }!
    29 | 
diff --git a/vlib/v/checker/tests/os_prefix.out b/vlib/v/checker/tests/os_prefix.out
index 4b87a6fff7..ac35b74c8c 100644
--- a/vlib/v/checker/tests/os_prefix.out
+++ b/vlib/v/checker/tests/os_prefix.out
@@ -1,7 +1,7 @@
 vlib/v/checker/tests/os_prefix.vv:1:8: warning: module 'os' is imported but never used
     1 | import os
       |        ~~
-    2 |
+    2 | 
     3 | fn main() {
 vlib/v/checker/tests/os_prefix.vv:5:12: error: unknown function: execute
     3 | fn main() {
@@ -10,6 +10,13 @@ vlib/v/checker/tests/os_prefix.vv:5:12: error: unknown function: execute
       |               ~~~~~~~~~~~~
     6 |     println(result)
     7 | }
+vlib/v/checker/tests/os_prefix.vv:5:9: error: assignment mismatch: 1 variable(s) but `execute()` returns 0 value(s)
+    3 | fn main() {
+    4 |     cmd := "ls"
+    5 |     result := execute(cmd)
+      |            ~~
+    6 |     println(result)
+    7 | }
 vlib/v/checker/tests/os_prefix.vv:6:2: error: `println` can not print void expressions
     4 |     cmd := "ls"
     5 |     result := execute(cmd)
diff --git a/vlib/v/checker/tests/par_expr_assign_void_right_type_err.out b/vlib/v/checker/tests/par_expr_assign_void_right_type_err.out
index 4945afaf0f..dfb7e4e85b 100644
--- a/vlib/v/checker/tests/par_expr_assign_void_right_type_err.out
+++ b/vlib/v/checker/tests/par_expr_assign_void_right_type_err.out
@@ -1,12 +1,6 @@
 vlib/v/checker/tests/par_expr_assign_void_right_type_err.vv:1:6: warning: redundant parentheses are used
     1 | _ := ((((print(10)))))
       |      ~~~~~~~~~~~~~~~~~
-vlib/v/checker/tests/par_expr_assign_void_right_type_err.vv:1:7: warning: redundant parentheses are used
-    1 | _ := ((((print(10)))))
-      |       ~~~~~~~~~~~~~~~
-vlib/v/checker/tests/par_expr_assign_void_right_type_err.vv:1:8: warning: redundant parentheses are used
-    1 | _ := ((((print(10)))))
-      |        ~~~~~~~~~~~~~
 vlib/v/checker/tests/par_expr_assign_void_right_type_err.vv:1:3: error: assignment mismatch: expected 1 value(s) but `print()` returns 0 value(s)
     1 | _ := ((((print(10)))))
       |   ~~
diff --git a/vlib/v/checker/tests/pointer_ops.out b/vlib/v/checker/tests/pointer_ops.out
index fa2d2abb02..6aa773f106 100644
--- a/vlib/v/checker/tests/pointer_ops.out
+++ b/vlib/v/checker/tests/pointer_ops.out
@@ -54,6 +54,13 @@ vlib/v/checker/tests/pointer_ops.vv:15:3: error: invalid operator `%` to `&Foo`
       |         ~~~~~~~
    16 |     }
    17 | }
+vlib/v/checker/tests/pointer_ops.vv:15:3: error: mismatched types `&Foo` and `int literal`
+   13 |         _ = p[3]
+   14 |         mut foo := &Foo{}
+   15 |         foo % 3
+      |         ~~~~~~~
+   16 |     }
+   17 | }
 vlib/v/checker/tests/pointer_ops.vv:22:7: error: `+` cannot be used with `voidptr`
    20 |     unsafe {
    21 |         mut p := nil
@@ -110,3 +117,10 @@ vlib/v/checker/tests/pointer_ops.vv:30:3: error: invalid operator `%` to `&Foo`
       |         ~~~~~~~
    31 |     }
    32 | }
+vlib/v/checker/tests/pointer_ops.vv:30:3: error: mismatched types `&Foo` and `int literal`
+   28 |         _ = p[3]
+   29 |         mut foo := &Foo{}
+   30 |         foo % 3
+      |         ~~~~~~~
+   31 |     }
+   32 | }
diff --git a/vlib/v/checker/tests/prefix_expr_decl_assign_err.out b/vlib/v/checker/tests/prefix_expr_decl_assign_err.out
index 70986913a0..fdbb4cf9e1 100644
--- a/vlib/v/checker/tests/prefix_expr_decl_assign_err.out
+++ b/vlib/v/checker/tests/prefix_expr_decl_assign_err.out
@@ -4,6 +4,12 @@ vlib/v/checker/tests/prefix_expr_decl_assign_err.vv:2:5: error: cannot use a ref
       |     ^
     3 |     (*d) := 14
     4 | }
+vlib/v/checker/tests/prefix_expr_decl_assign_err.vv:2:5: error: non-name on the left side of `:=`
+    1 | fn main() {
+    2 |     &a := 12
+      |     ^
+    3 |     (*d) := 14
+    4 | }
 vlib/v/checker/tests/prefix_expr_decl_assign_err.vv:3:5: error: non-name `(*d)` on left side of `:=`
     1 | fn main() {
     2 |     &a := 12
diff --git a/vlib/v/checker/tests/res_use_outside_defer.out b/vlib/v/checker/tests/res_use_outside_defer.out
index 54122a0db0..42f09b0f46 100644
--- a/vlib/v/checker/tests/res_use_outside_defer.out
+++ b/vlib/v/checker/tests/res_use_outside_defer.out
@@ -4,3 +4,9 @@ vlib/v/checker/tests/res_use_outside_defer.vv:2:10: error: `res` can only be use
       |             ~~~~~~
     3 |     return 'test'
     4 | }
+vlib/v/checker/tests/res_use_outside_defer.vv:2:2: error: `println` can not print void expressions
+    1 | fn test() string {
+    2 |     println($res())
+      |     ~~~~~~~~~~~~~~~
+    3 |     return 'test'
+    4 | }
diff --git a/vlib/v/checker/tests/result_type_call_err.out b/vlib/v/checker/tests/result_type_call_err.out
index c8b79f74ec..e4c945d5d6 100644
--- a/vlib/v/checker/tests/result_type_call_err.out
+++ b/vlib/v/checker/tests/result_type_call_err.out
@@ -4,3 +4,15 @@ vlib/v/checker/tests/result_type_call_err.vv:12:2: error: new_foo() returns a Re
    12 |     new_foo().foo()
       |     ~~~~~~~~~
    13 | }
+vlib/v/checker/tests/result_type_call_err.vv:12:2: error: Result type cannot be called directly
+   10 | 
+   11 | fn main() {
+   12 |     new_foo().foo()
+      |     ~~~~~~~~~
+   13 | }
+vlib/v/checker/tests/result_type_call_err.vv:12:12: error: foo() returns a Result, so it should have either an `or {}` block, or `!` at the end
+   10 | 
+   11 | fn main() {
+   12 |     new_foo().foo()
+      |               ~~~~~
+   13 | }
diff --git a/vlib/v/checker/tests/rshift_op_wrong_left_type_err.out b/vlib/v/checker/tests/rshift_op_wrong_left_type_err.out
index 60866d5051..b2fd31a4a0 100644
--- a/vlib/v/checker/tests/rshift_op_wrong_left_type_err.out
+++ b/vlib/v/checker/tests/rshift_op_wrong_left_type_err.out
@@ -3,3 +3,8 @@ vlib/v/checker/tests/rshift_op_wrong_left_type_err.vv:2:10: error: invalid opera
     2 |     println(0.5 >> 1)
       |             ~~~
     3 | }
+vlib/v/checker/tests/rshift_op_wrong_left_type_err.vv:2:2: error: `println` can not print void expressions
+    1 | fn main() {
+    2 |     println(0.5 >> 1)
+      |     ~~~~~~~~~~~~~~~~~
+    3 | }
diff --git a/vlib/v/checker/tests/rshift_op_wrong_right_type_err.out b/vlib/v/checker/tests/rshift_op_wrong_right_type_err.out
index 7a0c5d9b86..d733fecd21 100644
--- a/vlib/v/checker/tests/rshift_op_wrong_right_type_err.out
+++ b/vlib/v/checker/tests/rshift_op_wrong_right_type_err.out
@@ -3,3 +3,8 @@ vlib/v/checker/tests/rshift_op_wrong_right_type_err.vv:2:15: error: cannot shift
     2 |     println(1 >> 0.5)
       |                  ~~~
     3 | }
+vlib/v/checker/tests/rshift_op_wrong_right_type_err.vv:2:2: error: `println` can not print void expressions
+    1 | fn main() {
+    2 |     println(1 >> 0.5)
+      |     ~~~~~~~~~~~~~~~~~
+    3 | }
diff --git a/vlib/v/checker/tests/shared_bad_args.out b/vlib/v/checker/tests/shared_bad_args.out
index e41873c5dc..6694a7a196 100644
--- a/vlib/v/checker/tests/shared_bad_args.out
+++ b/vlib/v/checker/tests/shared_bad_args.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/shared_bad_args.vv:43:8: error: `r` is `shared` and must be
       |              ^
    44 |         println(u)
    45 |     }
+vlib/v/checker/tests/shared_bad_args.vv:43:8: error: `r` is `shared` and must be `rlock`ed or `lock`ed to be used as non-mut right-hand side of assignment
+   41 |     shared r := Qr{ a: 7 }
+   42 |     lock s {
+   43 |         u := r.s_val(s)
+      |              ^
+   44 |         println(u)
+   45 |     }
 vlib/v/checker/tests/shared_bad_args.vv:47:16: error: `s` is `shared` and must be `rlock`ed or `lock`ed to be passed as non-mut argument
    45 |     }
    46 |     lock r {
@@ -33,6 +40,13 @@ vlib/v/checker/tests/shared_bad_args.vv:61:3: error: r must be added to the `loc
       |         ^
    62 |     }
    63 |     lock r {
+vlib/v/checker/tests/shared_bad_args.vv:61:3: error: r is `shared` and must be `lock`ed to be passed as `mut`
+   59 |     shared r := Qr{ a: 7 }
+   60 |     lock s {
+   61 |         r.s_mut(mut s)
+      |         ^
+   62 |     }
+   63 |     lock r {
 vlib/v/checker/tests/shared_bad_args.vv:64:15: error: s must be added to the `lock` list above
    62 |     }
    63 |     lock r {
@@ -40,6 +54,13 @@ vlib/v/checker/tests/shared_bad_args.vv:64:15: error: s must be added to the `lo
       |                     ^
    65 |     }
    66 |     m_mut(mut m)
+vlib/v/checker/tests/shared_bad_args.vv:64:15: error: s is `shared` and must be `lock`ed to be passed as `mut`
+   62 |     }
+   63 |     lock r {
+   64 |         r.s_mut(mut s)
+      |                     ^
+   65 |     }
+   66 |     m_mut(mut m)
 vlib/v/checker/tests/shared_bad_args.vv:66:12: error: m is `shared` and must be `lock`ed to be passed as `mut`
    64 |         r.s_mut(mut s)
    65 |     }
diff --git a/vlib/v/checker/tests/shared_lock.out b/vlib/v/checker/tests/shared_lock.out
index 62d71304a4..2758fd3959 100644
--- a/vlib/v/checker/tests/shared_lock.out
+++ b/vlib/v/checker/tests/shared_lock.out
@@ -12,6 +12,13 @@ vlib/v/checker/tests/shared_lock.vv:20:7: error: method with `shared` arguments
       |             ^
    21 |         f(0, x)
    22 |     }
+vlib/v/checker/tests/shared_lock.vv:20:7: error: method `m` parameter `x` is `shared`, so use `shared x` instead
+   18 |     lock x {
+   19 |         x.r(x)
+   20 |         x.m(x)
+      |             ^
+   21 |         f(0, x)
+   22 |     }
 vlib/v/checker/tests/shared_lock.vv:21:8: error: function with `shared` arguments cannot be called inside `lock`/`rlock` block
    19 |         x.r(x)
    20 |         x.m(x)
@@ -19,3 +26,10 @@ vlib/v/checker/tests/shared_lock.vv:21:8: error: function with `shared` argument
       |              ^
    22 |     }
    23 | }
+vlib/v/checker/tests/shared_lock.vv:21:8: error: function `f` parameter `x` is `shared`, so use `shared x` instead
+   19 |         x.r(x)
+   20 |         x.m(x)
+   21 |         f(0, x)
+      |              ^
+   22 |     }
+   23 | }
diff --git a/vlib/v/checker/tests/shift_op_wrong_left_type_err.out b/vlib/v/checker/tests/shift_op_wrong_left_type_err.out
index 1bdeb5e2e2..8cfca1439b 100644
--- a/vlib/v/checker/tests/shift_op_wrong_left_type_err.out
+++ b/vlib/v/checker/tests/shift_op_wrong_left_type_err.out
@@ -3,3 +3,8 @@ vlib/v/checker/tests/shift_op_wrong_left_type_err.vv:2:10: error: invalid operat
     2 |     println(0.5 << 1)
       |             ~~~
     3 | }
+vlib/v/checker/tests/shift_op_wrong_left_type_err.vv:2:2: error: `println` can not print void expressions
+    1 | fn main() {
+    2 |     println(0.5 << 1)
+      |     ~~~~~~~~~~~~~~~~~
+    3 | }
diff --git a/vlib/v/checker/tests/shift_op_wrong_right_type_err.out b/vlib/v/checker/tests/shift_op_wrong_right_type_err.out
index 87d0a44972..7381ce6ee8 100644
--- a/vlib/v/checker/tests/shift_op_wrong_right_type_err.out
+++ b/vlib/v/checker/tests/shift_op_wrong_right_type_err.out
@@ -3,3 +3,8 @@ vlib/v/checker/tests/shift_op_wrong_right_type_err.vv:2:15: error: cannot shift
     2 |     println(1 << 0.5)
       |                  ~~~
     3 | }
+vlib/v/checker/tests/shift_op_wrong_right_type_err.vv:2:2: error: `println` can not print void expressions
+    1 | fn main() {
+    2 |     println(1 << 0.5)
+      |     ~~~~~~~~~~~~~~~~~
+    3 | }
diff --git a/vlib/v/checker/tests/shift_ops_expressions.out b/vlib/v/checker/tests/shift_ops_expressions.out
index 7823c17689..cad80513eb 100644
--- a/vlib/v/checker/tests/shift_ops_expressions.out
+++ b/vlib/v/checker/tests/shift_ops_expressions.out
@@ -19,27 +19,6 @@ vlib/v/checker/tests/shift_ops_expressions.vv:8:17: notice: shifting a value fro
       |                    ^
     9 |     println(c)
    10 |     a << 1
-vlib/v/checker/tests/shift_ops_expressions.vv:8:17: notice: shifting a value from a signed type `int` can change the sign
-    6 |         a << 2
-    7 |     }
-    8 |     c := if true { a << 111 } else { a << 333 }
-      |                    ^
-    9 |     println(c)
-   10 |     a << 1
-vlib/v/checker/tests/shift_ops_expressions.vv:8:35: notice: shifting a value from a signed type `int` can change the sign
-    6 |         a << 2
-    7 |     }
-    8 |     c := if true { a << 111 } else { a << 333 }
-      |                                      ^
-    9 |     println(c)
-   10 |     a << 1
-vlib/v/checker/tests/shift_ops_expressions.vv:8:35: notice: shifting a value from a signed type `int` can change the sign
-    6 |         a << 2
-    7 |     }
-    8 |     c := if true { a << 111 } else { a << 333 }
-      |                                      ^
-    9 |     println(c)
-   10 |     a << 1
 vlib/v/checker/tests/shift_ops_expressions.vv:10:2: notice: shifting a value from a signed type `int` can change the sign
     8 |     c := if true { a << 111 } else { a << 333 }
     9 |     println(c)
@@ -117,6 +96,13 @@ vlib/v/checker/tests/shift_ops_expressions.vv:37:8: error: shift count for type
       |              ~~~~
    38 |         println('---')
    39 |         555
+vlib/v/checker/tests/shift_ops_expressions.vv:37:3: error: unused expression
+   35 |     } else {
+   36 |         println('---')
+   37 |         a << 9999
+      |         ~~~~~~~~~
+   38 |         println('---')
+   39 |         555
 vlib/v/checker/tests/shift_ops_expressions.vv:50:23: error: shift count for type `int` too large (maximum: 31 bits)
    48 |         rr >> 2
    49 |     }
diff --git a/vlib/v/checker/tests/static_method_not_found_err.out b/vlib/v/checker/tests/static_method_not_found_err.out
index 0cd3b82822..2c74bf69c1 100644
--- a/vlib/v/checker/tests/static_method_not_found_err.out
+++ b/vlib/v/checker/tests/static_method_not_found_err.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/static_method_not_found_err.vv:10:9: error: unknown functio
       |            ~~~~~~~~~~~~~~~~~~~~~~~~~~
    11 |     println(val)
    12 | }
+vlib/v/checker/tests/static_method_not_found_err.vv:10:6: error: assignment mismatch: 1 variable(s) but `TestStruct.static_method()` returns 0 value(s)
+    8 | 
+    9 | fn main() {
+   10 |     val := TestStruct.static_method()
+      |         ~~
+   11 |     println(val)
+   12 | }
 vlib/v/checker/tests/static_method_not_found_err.vv:11:2: error: `println` can not print void expressions
     9 | fn main() {
    10 |     val := TestStruct.static_method()
diff --git a/vlib/v/checker/tests/str_method_return_string.out b/vlib/v/checker/tests/str_method_return_string.out
index 43bb36a3b8..9e9b35de9e 100644
--- a/vlib/v/checker/tests/str_method_return_string.out
+++ b/vlib/v/checker/tests/str_method_return_string.out
@@ -1,4 +1,11 @@
-vlib/v/checker/tests/str_method_return_string.vv:5:1: error: .str() methods should return `string` 
+vlib/v/checker/tests/str_method_return_string.vv:5:1: error: .str() methods should return `string`
+    3 | }
+    4 | 
+    5 | fn (z Zzz) str(x int) int {
+      | ~~~~~~~~~~~~~~~~~~~~~~~~~
+    6 |     return z.x
+    7 | }
+vlib/v/checker/tests/str_method_return_string.vv:5:1: error: .str() methods should have 0 arguments
     3 | }
     4 | 
     5 | fn (z Zzz) str(x int) int {
diff --git a/vlib/v/checker/tests/string_interpolation_wrong_fmt.out b/vlib/v/checker/tests/string_interpolation_wrong_fmt.out
index 4c9d7aea2f..b989948046 100644
--- a/vlib/v/checker/tests/string_interpolation_wrong_fmt.out
+++ b/vlib/v/checker/tests/string_interpolation_wrong_fmt.out
@@ -1,60 +1,67 @@
-vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:3:16: error: precision specification only valid for float types 
+vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:3:16: error: precision specification only valid for float types
     1 | fn interpolate_str() string {
     2 |     a := 'hallo'
     3 |     x := '>${a:8.3s}<'
       |                   ^
     4 |     y := '${a:G}'
     5 |     z := '${a:d}'
-vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:4:12: error: illegal format specifier `G` for type `string` 
+vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:4:12: error: illegal format specifier `G` for type `string`
     2 |     a := 'hallo'
     3 |     x := '>${a:8.3s}<'
     4 |     y := '${a:G}'
       |               ^
     5 |     z := '${a:d}'
     6 |     return x + y + z
-vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:5:12: error: illegal format specifier `d` for type `string` 
+vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:5:12: error: illegal format specifier `d` for type `string`
     3 |     x := '>${a:8.3s}<'
     4 |     y := '${a:G}'
     5 |     z := '${a:d}'
       |               ^
     6 |     return x + y + z
     7 | }
-vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:11:15: error: illegal format specifier `s` for type `f64` 
+vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:11:15: error: illegal format specifier `s` for type `f64`
     9 | fn interpolate_f64() string {
    10 |     b := 1367.57
    11 |     x := '>${b:20s}<'
       |                  ^
    12 |     y := '${b:d}'
    13 |     return x + y
-vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:12:12: error: illegal format specifier `d` for type `f64` 
+vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:12:12: error: illegal format specifier `d` for type `f64`
    10 |     b := 1367.57
    11 |     x := '>${b:20s}<'
    12 |     y := '${b:d}'
       |               ^
    13 |     return x + y
    14 | }
-vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:19:14: error: illegal format specifier `d` for type `u32` 
+vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:19:14: error: illegal format specifier `d` for type `u32`
    17 |     u := u32(15)
    18 |     s := -12
    19 |     x := '${u:13d}'
       |                 ^
    20 |     y := '${s:04u}'
    21 |     z := '${s:f}'
-vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:20:14: error: illegal format specifier `u` for type `int` 
+vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:20:14: error: illegal format specifier `u` for type `int`
    18 |     s := -12
    19 |     x := '${u:13d}'
    20 |     y := '${s:04u}'
       |                 ^
    21 |     z := '${s:f}'
    22 |     q := '${u:v}'
-vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:21:12: error: illegal format specifier `f` for type `int` 
+vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:21:12: error: illegal format specifier `f` for type `int`
    19 |     x := '${u:13d}'
    20 |     y := '${s:04u}'
    21 |     z := '${s:f}'
       |               ^
    22 |     q := '${u:v}'
    23 |     return x + y + z + q
-vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:22:12: error: unknown format specifier `v` 
+vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:22:12: error: unknown format specifier `v`
+   20 |     y := '${s:04u}'
+   21 |     z := '${s:f}'
+   22 |     q := '${u:v}'
+      |               ^
+   23 |     return x + y + z + q
+   24 | }
+vlib/v/checker/tests/string_interpolation_wrong_fmt.vv:22:12: error: illegal format specifier `v` for type `u32`
    20 |     y := '${s:04u}'
    21 |     z := '${s:f}'
    22 |     q := '${u:v}'
diff --git a/vlib/v/checker/tests/struct_embed_required_field_err.out b/vlib/v/checker/tests/struct_embed_required_field_err.out
index 94ce63bcf9..5786f7e0aa 100644
--- a/vlib/v/checker/tests/struct_embed_required_field_err.out
+++ b/vlib/v/checker/tests/struct_embed_required_field_err.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/struct_embed_required_field_err.vv:12:7: error: field `Bar.
       |          ~~~~~
    13 |         foo: 1
    14 |     }
+vlib/v/checker/tests/struct_embed_required_field_err.vv:12:7: error: field `Foo.bar` must be initialized
+   10 | 
+   11 | fn main() {
+   12 |     b := Bar {
+      |          ~~~~~
+   13 |         foo: 1
+   14 |     }
diff --git a/vlib/v/checker/tests/struct_field_assign_internal_types_nil_err.out b/vlib/v/checker/tests/struct_field_assign_internal_types_nil_err.out
index 2503d7d3eb..37b765408b 100644
--- a/vlib/v/checker/tests/struct_field_assign_internal_types_nil_err.out
+++ b/vlib/v/checker/tests/struct_field_assign_internal_types_nil_err.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/struct_field_assign_internal_types_nil_err.vv:15:8: error: cannot assign `nil` to struct field `name` with type `string`
-   13 |
+   13 | 
    14 | a := &Foo{
    15 |     name: unsafe { nil }
       |           ~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/struct_field_reference_type_err.out b/vlib/v/checker/tests/struct_field_reference_type_err.out
index 534556e123..72fe73b1f9 100644
--- a/vlib/v/checker/tests/struct_field_reference_type_err.out
+++ b/vlib/v/checker/tests/struct_field_reference_type_err.out
@@ -1,12 +1,19 @@
 vlib/v/checker/tests/struct_field_reference_type_err.vv:12:16: error: reference field `Animal.duck.age` must be initialized (part of struct `Duck`)
-   10 |
+   10 | 
+   11 | fn main() {
+   12 |     mut animal := Animal{
+      |                   ~~~~~~~
+   13 |         ageee: 20
+   14 |     }
+vlib/v/checker/tests/struct_field_reference_type_err.vv:12:16: error: reference field `Duck.age` must be initialized
+   10 | 
    11 | fn main() {
    12 |     mut animal := Animal{
       |                   ~~~~~~~
    13 |         ageee: 20
    14 |     }
 vlib/v/checker/tests/struct_field_reference_type_err.vv:17:3: error: reference field must be initialized with reference
-   15 |
+   15 | 
    16 |     animal.duck = Duck{
    17 |         age: animal.ageee
       |         ~~~~~~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/struct_field_type_err.out b/vlib/v/checker/tests/struct_field_type_err.out
index 53da8cf6ff..ee47700fc7 100644
--- a/vlib/v/checker/tests/struct_field_type_err.out
+++ b/vlib/v/checker/tests/struct_field_type_err.out
@@ -35,9 +35,16 @@ vlib/v/checker/tests/struct_field_type_err.vv:16:3: error: cannot assign to fiel
       |         ~~~~~~~~~~
    17 |     }
    18 |
-vlib/v/checker/tests/struct_field_type_err.vv:19:11: error: cannot assign to `data.n`: expected `int`, not `bool`
+vlib/v/checker/tests/struct_field_type_err.vv:16:3: error: reference field must be initialized with reference
+   14 |         f1: fn (v ...voidptr) {}
+   15 |         f2: fn (v voidptr) {}
+   16 |         data: true
+      |         ~~~~~~~~~~
    17 |     }
    18 |
+vlib/v/checker/tests/struct_field_type_err.vv:19:11: error: cannot assign to `data.n`: expected `int`, not `bool`
+   17 |     }
+   18 | 
    19 |     data.n = true
       |              ~~~~
    20 | }
diff --git a/vlib/v/checker/tests/struct_field_with_default_err.out b/vlib/v/checker/tests/struct_field_with_default_err.out
index e3aae1b330..3d9c819012 100644
--- a/vlib/v/checker/tests/struct_field_with_default_err.out
+++ b/vlib/v/checker/tests/struct_field_with_default_err.out
@@ -4,3 +4,9 @@ vlib/v/checker/tests/struct_field_with_default_err.vv:2:22: error: unknown struc
       |                         ~~~
     3 | }
     4 |
+vlib/v/checker/tests/struct_field_with_default_err.vv:2:22: error: incompatible initializer for field `arbitrary_field`: expected `T`, not `void`
+    1 | struct Dummy[T] {
+    2 |     arbitrary_field T = T{}
+      |                         ~~~
+    3 | }
+    4 |
diff --git a/vlib/v/checker/tests/struct_pub_field.out b/vlib/v/checker/tests/struct_pub_field.out
index c0c34c7c83..60de44ac3e 100644
--- a/vlib/v/checker/tests/struct_pub_field.out
+++ b/vlib/v/checker/tests/struct_pub_field.out
@@ -4,3 +4,9 @@ vlib/v/checker/tests/struct_pub_field.vv:9:4: error: field `i` of struct `Foo` i
     9 |     a.i = 2
       |       ^
    10 | }
+vlib/v/checker/tests/struct_pub_field.vv:9:2: error: `a` is immutable, declare it with `mut` to make it mutable
+    7 |         i: 1
+    8 |     }
+    9 |     a.i = 2
+      |     ^
+   10 | }
diff --git a/vlib/v/checker/tests/struct_ref_fields_uninitialized_err.out b/vlib/v/checker/tests/struct_ref_fields_uninitialized_err.out
index 1636e861f1..0ce3317fd6 100644
--- a/vlib/v/checker/tests/struct_ref_fields_uninitialized_err.out
+++ b/vlib/v/checker/tests/struct_ref_fields_uninitialized_err.out
@@ -1,5 +1,19 @@
 vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:25:7: error: reference field `Outer.c1.b` must be initialized (part of struct `ContainsRef`)
-   23 |
+   23 | 
+   24 | fn main() {
+   25 |     _ := Outer{}
+      |          ~~~~~~~
+   26 |     _ := Struct{}
+   27 | }
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:25:7: error: reference field `ContainsRef.b` must be initialized
+   23 | 
+   24 | fn main() {
+   25 |     _ := Outer{}
+      |          ~~~~~~~
+   26 |     _ := Struct{}
+   27 | }
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:25:7: error: reference field `Outer.c2.b` must be initialized (part of struct `ContainsRef`)
+   23 | 
    24 | fn main() {
    25 |     _ := Outer{}
       |          ~~~~~~~
@@ -11,3 +25,9 @@ vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:26:7: error: referen
    26 |     _ := Struct{}
       |          ~~~~~~~~
    27 | }
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:26:7: error: reference field `EmbedStruct.ref2` must be initialized
+   24 | fn main() {
+   25 |     _ := Outer{}
+   26 |     _ := Struct{}
+      |          ~~~~~~~~
+   27 | }
diff --git a/vlib/v/checker/tests/struct_voidptr_field_no_ptr_struct_value_err.out b/vlib/v/checker/tests/struct_voidptr_field_no_ptr_struct_value_err.out
index 606535797b..d06ca9b20b 100644
--- a/vlib/v/checker/tests/struct_voidptr_field_no_ptr_struct_value_err.out
+++ b/vlib/v/checker/tests/struct_voidptr_field_no_ptr_struct_value_err.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/struct_voidptr_field_no_ptr_struct_value_err.vv:11:3: error
       |         ~~~~~~~~
    12 |     }
    13 | }
+vlib/v/checker/tests/struct_voidptr_field_no_ptr_struct_value_err.vv:11:3: error: cannot assign to field `a`: expected a pointer `voidptr`, but got `Foo`
+    9 | fn main() {
+   10 |     _ := Foo2{
+   11 |         a: Foo{}
+      |         ~~~~~~~~
+   12 |     }
+   13 | }
diff --git a/vlib/v/checker/tests/sum_type_common_fields_alias_error.out b/vlib/v/checker/tests/sum_type_common_fields_alias_error.out
index 20c3b008b0..79f268b3f9 100644
--- a/vlib/v/checker/tests/sum_type_common_fields_alias_error.out
+++ b/vlib/v/checker/tests/sum_type_common_fields_alias_error.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/sum_type_common_fields_alias_error.vv:35:14: error: field `
       |                 ~~~~
    36 |     assert m[1].name == 'def'
    37 |     assert m[2].name == 'xyz'
+vlib/v/checker/tests/sum_type_common_fields_alias_error.vv:35:9: error: assert can be used only with `bool` expressions, but found `void` instead
+   33 |     }
+   34 |     println(m)
+   35 |     assert m[0].name == 'abc'
+      |            ~~~~~~~~~~~~~~~~~~
+   36 |     assert m[1].name == 'def'
+   37 |     assert m[2].name == 'xyz'
 vlib/v/checker/tests/sum_type_common_fields_alias_error.vv:36:14: error: field `name` does not exist or have the same type in all sumtype variants
    34 |     println(m)
    35 |     assert m[0].name == 'abc'
@@ -12,9 +19,22 @@ vlib/v/checker/tests/sum_type_common_fields_alias_error.vv:36:14: error: field `
       |                 ~~~~
    37 |     assert m[2].name == 'xyz'
    38 | }
+vlib/v/checker/tests/sum_type_common_fields_alias_error.vv:36:9: error: assert can be used only with `bool` expressions, but found `void` instead
+   34 |     println(m)
+   35 |     assert m[0].name == 'abc'
+   36 |     assert m[1].name == 'def'
+      |            ~~~~~~~~~~~~~~~~~~
+   37 |     assert m[2].name == 'xyz'
+   38 | }
 vlib/v/checker/tests/sum_type_common_fields_alias_error.vv:37:14: error: field `name` does not exist or have the same type in all sumtype variants
    35 |     assert m[0].name == 'abc'
    36 |     assert m[1].name == 'def'
    37 |     assert m[2].name == 'xyz'
       |                 ~~~~
    38 | }
+vlib/v/checker/tests/sum_type_common_fields_alias_error.vv:37:9: error: assert can be used only with `bool` expressions, but found `void` instead
+   35 |     assert m[0].name == 'abc'
+   36 |     assert m[1].name == 'def'
+   37 |     assert m[2].name == 'xyz'
+      |            ~~~~~~~~~~~~~~~~~~
+   38 | }
diff --git a/vlib/v/checker/tests/sum_type_common_fields_error.out b/vlib/v/checker/tests/sum_type_common_fields_error.out
index 9dce91ab09..ec05ff5b74 100644
--- a/vlib/v/checker/tests/sum_type_common_fields_error.out
+++ b/vlib/v/checker/tests/sum_type_common_fields_error.out
@@ -4,3 +4,9 @@ vlib/v/checker/tests/sum_type_common_fields_error.vv:53:14: error: field `val` d
    53 |     assert m[0].val == 123
       |                 ~~~
    54 | }
+vlib/v/checker/tests/sum_type_common_fields_error.vv:53:9: error: assert can be used only with `bool` expressions, but found `void` instead
+   51 |     assert m[2].name == '64bit integer'
+   52 |     assert m[3].name == 'string'
+   53 |     assert m[0].val == 123
+      |            ~~~~~~~~~~~~~~~
+   54 | }
diff --git a/vlib/v/checker/tests/sum_type_exists.out b/vlib/v/checker/tests/sum_type_exists.out
index 03597f0a98..ab144c58ae 100644
--- a/vlib/v/checker/tests/sum_type_exists.out
+++ b/vlib/v/checker/tests/sum_type_exists.out
@@ -1,3 +1,6 @@
 vlib/v/checker/tests/sum_type_exists.vv:1:22: error: unknown type `Inexistent`
     1 | type Miscellaneous = Inexistent | Nope | int
-      |                      ~~~~~~~~~~
\ No newline at end of file
+      |                      ~~~~~~~~~~
+vlib/v/checker/tests/sum_type_exists.vv:1:35: error: unknown type `Nope`
+    1 | type Miscellaneous = Inexistent | Nope | int
+      |                                   ~~~~
diff --git a/vlib/v/checker/tests/sum_type_infix_err.out b/vlib/v/checker/tests/sum_type_infix_err.out
index 6a06f1b90c..4a6662a5bb 100644
--- a/vlib/v/checker/tests/sum_type_infix_err.out
+++ b/vlib/v/checker/tests/sum_type_infix_err.out
@@ -12,3 +12,10 @@ vlib/v/checker/tests/sum_type_infix_err.vv:6:11: error: cannot use operator `+`
       |              ^
     7 |     _ = unsafe{&x + 5}
     8 | }
+vlib/v/checker/tests/sum_type_infix_err.vv:6:7: error: infix expr: cannot use `Abc` (right expression) as `int literal`
+    4 |     x := Abc(0)
+    5 |     _ := x + Abc(5)
+    6 |     _ := 123 + x
+      |          ~~~~~~~
+    7 |     _ = unsafe{&x + 5}
+    8 | }
diff --git a/vlib/v/checker/tests/sum_type_mutable_cast_err.out b/vlib/v/checker/tests/sum_type_mutable_cast_err.out
index a880221f43..89423de77b 100644
--- a/vlib/v/checker/tests/sum_type_mutable_cast_err.out
+++ b/vlib/v/checker/tests/sum_type_mutable_cast_err.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/sum_type_mutable_cast_err.vv:15:10: error: cannot use opera
       |                ^
    16 |     }
    17 |     mut f := Foo{Bar{Abc(0)}}
+vlib/v/checker/tests/sum_type_mutable_cast_err.vv:15:8: error: infix expr: cannot use `int literal` (right expression) as `Abc`
+   13 |     mut x := Abc(0)
+   14 |     if x is int {
+   15 |         _ := x + 5
+      |              ~~~~~
+   16 |     }
+   17 |     mut f := Foo{Bar{Abc(0)}}
 vlib/v/checker/tests/sum_type_mutable_cast_err.vv:19:14: error: cannot use operator `+` with `Abc`
    17 |     mut f := Foo{Bar{Abc(0)}}
    18 |     if f.b.a is int {
@@ -12,3 +19,10 @@ vlib/v/checker/tests/sum_type_mutable_cast_err.vv:19:14: error: cannot use opera
       |                    ^
    20 |     }
    21 | }
+vlib/v/checker/tests/sum_type_mutable_cast_err.vv:19:12: error: infix expr: cannot use `int literal` (right expression) as `Abc`
+   17 |     mut f := Foo{Bar{Abc(0)}}
+   18 |     if f.b.a is int {
+   19 |         _ := f.b.a + 5
+      |                  ~~~~~
+   20 |     }
+   21 | }
diff --git a/vlib/v/checker/tests/test_functions_wrong_signature_test.out b/vlib/v/checker/tests/test_functions_wrong_signature_test.out
index b544f0aa09..79704baf0f 100644
--- a/vlib/v/checker/tests/test_functions_wrong_signature_test.out
+++ b/vlib/v/checker/tests/test_functions_wrong_signature_test.out
@@ -1,12 +1,19 @@
 vlib/v/checker/tests/test_functions_wrong_signature_test.vv:9:1: error: test functions should either return nothing at all, or be marked to return `?` or `!`
-    7 |
+    7 | 
+    8 | // should be disallowed:
+    9 | fn test_returning_int() int {
+      | ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+   10 | }
+   11 |
+vlib/v/checker/tests/test_functions_wrong_signature_test.vv:9:1: error: missing return at end of function `test_returning_int`
+    7 | 
     8 | // should be disallowed:
     9 | fn test_returning_int() int {
       | ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    10 | }
    11 |
 vlib/v/checker/tests/test_functions_wrong_signature_test.vv:19:1: error: test functions should take 0 parameters
-   17 |
+   17 | 
    18 | // should be disallowed:
    19 | fn test_take_parameters(v int) {
       | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/top_level_fn_builtin_decl_err.out b/vlib/v/checker/tests/top_level_fn_builtin_decl_err.out
index 82a7bb7718..4cdeaa5712 100644
--- a/vlib/v/checker/tests/top_level_fn_builtin_decl_err.out
+++ b/vlib/v/checker/tests/top_level_fn_builtin_decl_err.out
@@ -1,28 +1,56 @@
 vlib/v/checker/tests/top_level_fn_builtin_decl_err.vv:3:1: error: top level declaration cannot shadow builtin type
-    1 |
+    1 | 
     2 | [inline]
     3 | fn char(ch byte) fn (string) !(byte, string) {
       | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     4 |     return fn [ch] (input string) !(byte, string) {
     5 |         return if input[0] == ch {
 vlib/v/checker/tests/top_level_fn_builtin_decl_err.vv:19:18: error: unknown function: a_char
-   17 |
+   17 | 
    18 |     for i, input in inputs {
    19 |         got, remain := a_char(input)!
       |                        ~~~~~~~~~~~~~
-   20 |
+   20 | 
+   21 |         assert got == 'a'[0]
+vlib/v/checker/tests/top_level_fn_builtin_decl_err.vv:19:31: error: unexpected `!`, the function `a_char` does not return a Result
+   17 | 
+   18 |     for i, input in inputs {
+   19 |         got, remain := a_char(input)!
+      |                                     ^
+   20 | 
+   21 |         assert got == 'a'[0]
+vlib/v/checker/tests/top_level_fn_builtin_decl_err.vv:19:15: error: assignment mismatch: 2 variable(s) but `a_char()` returns 0 value(s)
+   17 | 
+   18 |     for i, input in inputs {
+   19 |         got, remain := a_char(input)!
+      |                     ~~
+   20 | 
    21 |         assert got == 'a'[0]
 vlib/v/checker/tests/top_level_fn_builtin_decl_err.vv:21:10: error: invalid variable `got`
    19 |         got, remain := a_char(input)!
-   20 |
+   20 | 
    21 |         assert got == 'a'[0]
       |                ~~~
    22 |         assert remain == remains[i]
    23 |     }
+vlib/v/checker/tests/top_level_fn_builtin_decl_err.vv:21:10: error: assert can be used only with `bool` expressions, but found `void` instead
+   19 |         got, remain := a_char(input)!
+   20 | 
+   21 |         assert got == 'a'[0]
+      |                ~~~~~~~~~~~~~
+   22 |         assert remain == remains[i]
+   23 |     }
 vlib/v/checker/tests/top_level_fn_builtin_decl_err.vv:22:10: error: invalid variable `remain`
-   20 |
+   20 | 
    21 |         assert got == 'a'[0]
    22 |         assert remain == remains[i]
       |                ~~~~~~
    23 |     }
    24 | }
+vlib/v/checker/tests/top_level_fn_builtin_decl_err.vv:22:10: error: assert can be used only with `bool` expressions, but found `void` instead
+   20 | 
+   21 |         assert got == 'a'[0]
+   22 |         assert remain == remains[i]
+      |                ~~~~~~~~~~~~~~~~~~~~
+   23 |     }
+   24 | }
diff --git a/vlib/v/checker/tests/uncasted_enum_val_as_size_for_fixed_array_err.out b/vlib/v/checker/tests/uncasted_enum_val_as_size_for_fixed_array_err.out
index 177bfd6429..02ffd53aac 100644
--- a/vlib/v/checker/tests/uncasted_enum_val_as_size_for_fixed_array_err.out
+++ b/vlib/v/checker/tests/uncasted_enum_val_as_size_for_fixed_array_err.out
@@ -1,13 +1,19 @@
 vlib/v/checker/tests/uncasted_enum_val_as_size_for_fixed_array_err.vv:10:7: error: Foo.first has to be casted to integer to be used as size
     8 | }
-    9 |
+    9 | 
    10 | a := [b]int{}
       |       ^
    11 | println(a)
    12 |
 vlib/v/checker/tests/uncasted_enum_val_as_size_for_fixed_array_err.vv:13:7: error: Foo.second has to be casted to integer to be used as size
    11 | println(a)
-   12 |
+   12 | 
+   13 | c := [Foo.second]int{}
+      |       ~~~~~~~~~~
+   14 | println(c)
+vlib/v/checker/tests/uncasted_enum_val_as_size_for_fixed_array_err.vv:13:7: error: fixed size cannot be zero or negative (fixed_size: 0)
+   11 | println(a)
+   12 | 
    13 | c := [Foo.second]int{}
       |       ~~~~~~~~~~
    14 | println(c)
diff --git a/vlib/v/checker/tests/undefined_ident_in_ref_selector.out b/vlib/v/checker/tests/undefined_ident_in_ref_selector.out
index d6f7c95f4e..ec09fd7c46 100644
--- a/vlib/v/checker/tests/undefined_ident_in_ref_selector.out
+++ b/vlib/v/checker/tests/undefined_ident_in_ref_selector.out
@@ -1,6 +1,25 @@
 vlib/v/checker/tests/undefined_ident_in_ref_selector.vv:6:10: error: undefined ident: `line`
-    4 |
+    4 | 
     5 | fn read() int {
     6 |     return &line.len
       |             ~~~~
     7 | }
+vlib/v/checker/tests/undefined_ident_in_ref_selector.vv:6:15: error: `line` does not return a value
+    4 | 
+    5 | fn read() int {
+    6 |     return &line.len
+      |                  ~~~
+    7 | }
+vlib/v/checker/tests/undefined_ident_in_ref_selector.vv:6:9: error: cannot use `void` as type `int` in return argument
+    4 | 
+    5 | fn read() int {
+    6 |     return &line.len
+      |            ^
+    7 | }
+vlib/v/checker/tests/undefined_ident_in_ref_selector.vv:6:9: error: fn `read` expects you to return a non reference type `int`, but you are returning `void` instead
+    4 | 
+    5 | fn read() int {
+    6 |     return &line.len
+      |            ^
+    7 | }
+Details: use `return *pointer` instead of `return pointer`, and just `return value` instead of `return &value`
diff --git a/vlib/v/checker/tests/undefined_ident_of_struct.out b/vlib/v/checker/tests/undefined_ident_of_struct.out
index 35e0a6cc6c..cf44156b52 100644
--- a/vlib/v/checker/tests/undefined_ident_of_struct.out
+++ b/vlib/v/checker/tests/undefined_ident_of_struct.out
@@ -1,7 +1,28 @@
 vlib/v/checker/tests/undefined_ident_of_struct.vv:4:2: error: undefined ident: `f`
-    2 |
+    2 | 
     3 | fn get()  {
     4 |     f.a = 'test'
       |     ^
     5 | }
     6 |
+vlib/v/checker/tests/undefined_ident_of_struct.vv:4:4: error: `f` does not return a value
+    2 | 
+    3 | fn get()  {
+    4 |     f.a = 'test'
+      |       ^
+    5 | }
+    6 |
+vlib/v/checker/tests/undefined_ident_of_struct.vv:4:4: error: unexpected symbol `void`
+    2 | 
+    3 | fn get()  {
+    4 |     f.a = 'test'
+      |       ^
+    5 | }
+    6 |
+vlib/v/checker/tests/undefined_ident_of_struct.vv:4:8: error: cannot assign to `f.a`: expected `void`, not `string`
+    2 | 
+    3 | fn get()  {
+    4 |     f.a = 'test'
+      |           ~~~~~~
+    5 | }
+    6 |
diff --git a/vlib/v/checker/tests/undefined_var_in_comptime_for_test.out b/vlib/v/checker/tests/undefined_var_in_comptime_for_test.out
index 0da1dc1fa9..84e65a16c2 100644
--- a/vlib/v/checker/tests/undefined_var_in_comptime_for_test.out
+++ b/vlib/v/checker/tests/undefined_var_in_comptime_for_test.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/undefined_var_in_comptime_for_test.vv:11:3: error: undefine
       |         ~~~~~~~~~~
    12 |         println(field)
    13 |     }
+vlib/v/checker/tests/undefined_var_in_comptime_for_test.vv:11:13: error: invalid operation: ++ (non-numeric type `void`)
+    9 | fn test[U](val U) {
+   10 |     $for field in U.fields {
+   11 |         fields_len++
+      |                   ~~
+   12 |         println(field)
+   13 |     }
diff --git a/vlib/v/checker/tests/unimplemented_interface_e.out b/vlib/v/checker/tests/unimplemented_interface_e.out
index 8181dbb4dc..cd754406a7 100644
--- a/vlib/v/checker/tests/unimplemented_interface_e.out
+++ b/vlib/v/checker/tests/unimplemented_interface_e.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/unimplemented_interface_e.vv:12:6: error: `Cat` incorrectly implements method `speak` of interface `Animal`: expected `string`, not `&string` for parameter 1
-   10 |
+   10 | 
    11 | fn main() {
    12 |     foo(Cat{})
       |         ~~~~~
@@ -15,3 +15,9 @@ vlib/v/checker/tests/unimplemented_interface_e.vv:13:6: error: `Cat` incorrectly
    14 | }
 Details: main.Animal has `fn speak(x main.Animal, s string)`
          main.Cat has `fn speak(c main.Cat, s &string)`
+vlib/v/checker/tests/unimplemented_interface_e.vv:13:6: error: `Cat` does not implement interface `Animal`, cannot cast `Cat` to interface `Animal`
+   11 | fn main() {
+   12 |     foo(Cat{})
+   13 |     _ = Animal(Cat{})
+      |         ~~~~~~~~~~~~~
+   14 | }
diff --git a/vlib/v/checker/tests/unknown_as_type.out b/vlib/v/checker/tests/unknown_as_type.out
index e520655b7b..9b87dfb531 100644
--- a/vlib/v/checker/tests/unknown_as_type.out
+++ b/vlib/v/checker/tests/unknown_as_type.out
@@ -1,6 +1,13 @@
 vlib/v/checker/tests/unknown_as_type.vv:7:9: error: unknown type `Stringg`.
 Did you mean `String`?
-    5 |
+    5 | 
+    6 | fn foo(e Expr) {
+    7 |     x := e as Stringg
+      |            ~~
+    8 |     println(x)
+    9 | }
+vlib/v/checker/tests/unknown_as_type.vv:7:9: error: cannot cast `Expr` to `Stringg`
+    5 | 
     6 | fn foo(e Expr) {
     7 |     x := e as Stringg
       |            ~~
diff --git a/vlib/v/checker/tests/unknown_comptime_expr.out b/vlib/v/checker/tests/unknown_comptime_expr.out
index f7eb905b4f..7e25e66067 100644
--- a/vlib/v/checker/tests/unknown_comptime_expr.out
+++ b/vlib/v/checker/tests/unknown_comptime_expr.out
@@ -19,6 +19,20 @@ vlib/v/checker/tests/unknown_comptime_expr.vv:17:6: error: undefined ident: `huh
       |         ~~~
    18 |     }
    19 |     $if s is int {
+vlib/v/checker/tests/unknown_comptime_expr.vv:17:10: error: `huh` does not return a value
+   15 | fn if_is() {
+   16 |     s := S1{}
+   17 |     $if huh.typ is T {
+      |             ~~~
+   18 |     }
+   19 |     $if s is int {
+vlib/v/checker/tests/unknown_comptime_expr.vv:17:17: error: unknown type `T`
+   15 | fn if_is() {
+   16 |     s := S1{}
+   17 |     $if huh.typ is T {
+      |                    ^
+   18 |     }
+   19 |     $if s is int {
 vlib/v/checker/tests/unknown_comptime_expr.vv:21:13: error: invalid `$if` condition: expected a type
    19 |     $if s is int {
    20 |     }
diff --git a/vlib/v/checker/tests/unknown_field.out b/vlib/v/checker/tests/unknown_field.out
index 395eedff82..09658bd6c8 100644
--- a/vlib/v/checker/tests/unknown_field.out
+++ b/vlib/v/checker/tests/unknown_field.out
@@ -4,3 +4,9 @@ vlib/v/checker/tests/unknown_field.vv:7:12: error: type `Test` has no field name
     7 |     println(t.sdd)
       |               ~~~
     8 | }
+vlib/v/checker/tests/unknown_field.vv:7:2: error: `println` can not print void expressions
+    5 | fn main() {
+    6 |     t := Test{}
+    7 |     println(t.sdd)
+      |     ~~~~~~~~~~~~~~
+    8 | }
diff --git a/vlib/v/checker/tests/unknown_function.out b/vlib/v/checker/tests/unknown_function.out
index 8acc209fa9..caf326d2b7 100644
--- a/vlib/v/checker/tests/unknown_function.out
+++ b/vlib/v/checker/tests/unknown_function.out
@@ -5,3 +5,9 @@ Did you mean `math.max`?
     4 |     println(math.max_i64())
       |                  ~~~~~~~~~
     5 | }
+vlib/v/checker/tests/unknown_function.vv:4:2: error: `println` can not print void expressions
+    2 | 
+    3 | fn main() {
+    4 |     println(math.max_i64())
+      |     ~~~~~~~~~~~~~~~~~~~~~~~
+    5 | }
diff --git a/vlib/v/checker/tests/unknown_method.out b/vlib/v/checker/tests/unknown_method.out
index 037d2f382e..15b48c69b6 100644
--- a/vlib/v/checker/tests/unknown_method.out
+++ b/vlib/v/checker/tests/unknown_method.out
@@ -4,3 +4,9 @@ vlib/v/checker/tests/unknown_method.vv:7:12: error: unknown method or field: `Te
     7 |     println(t.sdd())
       |               ~~~~~
     8 | }
+vlib/v/checker/tests/unknown_method.vv:7:2: error: `println` can not print void expressions
+    5 | fn main() {
+    6 |     t := Test{}
+    7 |     println(t.sdd())
+      |     ~~~~~~~~~~~~~~~~
+    8 | }
diff --git a/vlib/v/checker/tests/unknown_method_suggest_name.out b/vlib/v/checker/tests/unknown_method_suggest_name.out
index acf5d1427b..e1160739c6 100644
--- a/vlib/v/checker/tests/unknown_method_suggest_name.out
+++ b/vlib/v/checker/tests/unknown_method_suggest_name.out
@@ -14,6 +14,13 @@ Did you mean `translate`?
       |            ~~~~~~~~~~~~
    28 |     println('p: $p')
    29 |     println('v: $v')
+vlib/v/checker/tests/unknown_method_suggest_name.vv:27:4: error: assignment mismatch: 1 variable(s) but `tranzlate()` returns 0 value(s)
+   25 |     p := Point{1, 2, 3}
+   26 |     v := Vector{x: 5, y: 5, z: 10}
+   27 |     z := p.tranzlate(v)
+      |       ~~
+   28 |     println('p: $p')
+   29 |     println('v: $v')
 vlib/v/checker/tests/unknown_method_suggest_name.vv:30:15: error: expression does not return a value
    28 |     println('p: $p')
    29 |     println('v: $v')
diff --git a/vlib/v/checker/tests/unknown_var_assign.out b/vlib/v/checker/tests/unknown_var_assign.out
index 6a12a8cbbc..dc1867dd1e 100644
--- a/vlib/v/checker/tests/unknown_var_assign.out
+++ b/vlib/v/checker/tests/unknown_var_assign.out
@@ -3,3 +3,8 @@ vlib/v/checker/tests/unknown_var_assign.vv:2:5: error: undefined ident: `x` (use
     2 |     x = 'hello v'
       |     ^
     3 | }
+vlib/v/checker/tests/unknown_var_assign.vv:2:9: error: cannot assign to `x`: expected `void`, not `string`
+    1 | fn main() {
+    2 |     x = 'hello v'
+      |         ~~~~~~~~~
+    3 | }
diff --git a/vlib/v/checker/tests/var_option_wrong_type.out b/vlib/v/checker/tests/var_option_wrong_type.out
index ce1a755fbd..532bdf75a9 100644
--- a/vlib/v/checker/tests/var_option_wrong_type.out
+++ b/vlib/v/checker/tests/var_option_wrong_type.out
@@ -4,3 +4,15 @@ vlib/v/checker/tests/var_option_wrong_type.vv:3:23: error: mismatched types `?f6
     3 | var3 := var_none or { var_none + 'foo' }
       |                       ~~~~~~~~~~~~~~~~
     4 | println(var3)
+vlib/v/checker/tests/var_option_wrong_type.vv:3:23: error: infix expr: cannot use `string` (right expression) as `f64`
+    1 | var_none := ?f64(none)
+    2 | 
+    3 | var3 := var_none or { var_none + 'foo' }
+      |                       ~~~~~~~~~~~~~~~~
+    4 | println(var3)
+vlib/v/checker/tests/var_option_wrong_type.vv:3:23: error: `or` block must provide a default value of type `f64`, or return/continue/break or call a [noreturn] function like panic(err) or exit(1)
+    1 | var_none := ?f64(none)
+    2 | 
+    3 | var3 := var_none or { var_none + 'foo' }
+      |                       ~~~~~~~~~~~~~~~~
+    4 | println(var3)
diff --git a/vlib/v/checker/tests/void_fn_as_value.out b/vlib/v/checker/tests/void_fn_as_value.out
index 9898c195be..f44853ec75 100644
--- a/vlib/v/checker/tests/void_fn_as_value.out
+++ b/vlib/v/checker/tests/void_fn_as_value.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/void_fn_as_value.vv:5:7: error: unknown function: x
       |          ~~~~~~~~~~
     6 |     mut b := 'abcdef'
     7 |     _ = b
+vlib/v/checker/tests/void_fn_as_value.vv:5:4: error: assignment mismatch: 1 variable(s) but `x()` returns 0 value(s)
+    3 | fn main() {
+    4 |     mut a := 'aa'
+    5 |     a += x('a','b')
+      |       ~~
+    6 |     mut b := 'abcdef'
+    7 |     _ = b
diff --git a/vlib/v/checker/tests/void_fn_multiple_ret_err.out b/vlib/v/checker/tests/void_fn_multiple_ret_err.out
index 24af8247e0..13431f8e13 100644
--- a/vlib/v/checker/tests/void_fn_multiple_ret_err.out
+++ b/vlib/v/checker/tests/void_fn_multiple_ret_err.out
@@ -11,6 +11,13 @@ vlib/v/checker/tests/void_fn_multiple_ret_err.vv:6:2: error: Option and Result t
       |     ~~~~~~~~~~~
     7 | }
     8 |
+vlib/v/checker/tests/void_fn_multiple_ret_err.vv:6:9: error: cannot use `none` as Result type in return argument
+    4 | 
+    5 | fn foo_result_2() ! {
+    6 |     return none
+      |            ~~~~
+    7 | }
+    8 |
 vlib/v/checker/tests/void_fn_multiple_ret_err.vv:14:9: error: cannot use `int literal` as Result type in return argument
    12 | 
    13 | fn foo_result_4() ! {
diff --git a/vlib/v/checker/tests/warnings_for_string_c2v_calls.out b/vlib/v/checker/tests/warnings_for_string_c2v_calls.out
index f570847a42..e87d1aabd6 100644
--- a/vlib/v/checker/tests/warnings_for_string_c2v_calls.out
+++ b/vlib/v/checker/tests/warnings_for_string_c2v_calls.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/warnings_for_string_c2v_calls.vv:8:7: error: to convert a C
       |          ~~~~~~~~~
     9 |     eprintln('x: $x')
    10 |     eprintln('x.len: $x.len')
+vlib/v/checker/tests/warnings_for_string_c2v_calls.vv:8:7: error: cannot cast pointer type `&u8` to string, use `&u8(p).vstring()` or `cstring_to_vstring(p)` instead.
+    6 |         p[2] = `z`
+    7 |     }
+    8 |     x := string(p)
+      |          ~~~~~~~~~
+    9 |     eprintln('x: $x')
+   10 |     eprintln('x.len: $x.len')
diff --git a/vlib/v/checker/tests/with_check_option/v_tictactoe.out b/vlib/v/checker/tests/with_check_option/v_tictactoe.out
index 8682a24390..6c5cc73b39 100644
--- a/vlib/v/checker/tests/with_check_option/v_tictactoe.out
+++ b/vlib/v/checker/tests/with_check_option/v_tictactoe.out
@@ -31,3 +31,10 @@ vlib/v/checker/tests/with_check_option/v_tictactoe.vv:6:14: error: unknown type
       |              ~~~~~~~
     7 |     }
     8 |     return board
+vlib/v/checker/tests/with_check_option/v_tictactoe.vv:6:21: error: unknown type for expression `board[i / 3]`
+    4 |     mut board := [3][]string{ len: 3, init: []string{ len: 3, init: '' } }
+    5 |     for i in 0..9 {
+    6 |         board[i / 3][i % 3] = (i + 1).str()
+      |                     ~~~~~~~
+    7 |     }
+    8 |     return board
diff --git a/vlib/v/checker/tests/wrong_fn_init_err.out b/vlib/v/checker/tests/wrong_fn_init_err.out
index 15aff9f9ae..489c1bf089 100644
--- a/vlib/v/checker/tests/wrong_fn_init_err.out
+++ b/vlib/v/checker/tests/wrong_fn_init_err.out
@@ -5,3 +5,10 @@ vlib/v/checker/tests/wrong_fn_init_err.vv:4:7: error: functions must be defined,
       |          ~~~~~~~~~~~~
     5 |     println(a)
     6 | }
+vlib/v/checker/tests/wrong_fn_init_err.vv:4:7: error: type `MyCallback` is private
+    2 | 
+    3 | fn main() {
+    4 |     a := MyCallback{}
+      |          ~~~~~~~~~~~~
+    5 |     println(a)
+    6 | }
diff --git a/vlib/v/checker/tests/wrong_propagate_ret_type.out b/vlib/v/checker/tests/wrong_propagate_ret_type.out
index 9687026366..1fcd559699 100644
--- a/vlib/v/checker/tests/wrong_propagate_ret_type.out
+++ b/vlib/v/checker/tests/wrong_propagate_ret_type.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/wrong_propagate_ret_type.vv:10:17: error: to propagate the Option call, `opt_call` must return an Option
-    8 |
+    8 | 
     9 | fn opt_call() int {
    10 |     a := ret_none()?
       |                    ^
@@ -7,13 +7,27 @@ vlib/v/checker/tests/wrong_propagate_ret_type.vv:10:17: error: to propagate the
    12 | }
 Details: vlib/v/checker/tests/wrong_propagate_ret_type.vv:9:15: details: prepend ? before the declaration of the return type of `opt_call`
     7 | }
-    8 |
+    8 | 
+    9 | fn opt_call() int {
+      |               ~~~
+   10 |     a := ret_none()?
+   11 |     return a
+vlib/v/checker/tests/wrong_propagate_ret_type.vv:10:17: error: to propagate the call, `opt_call` must return an Option type
+    8 | 
+    9 | fn opt_call() int {
+   10 |     a := ret_none()?
+      |                    ^
+   11 |     return a
+   12 | }
+Details: vlib/v/checker/tests/wrong_propagate_ret_type.vv:9:15: details: prepend ? before the declaration of the return type of `opt_call`
+    7 | }
+    8 | 
     9 | fn opt_call() int {
       |               ~~~
    10 |     a := ret_none()?
    11 |     return a
 vlib/v/checker/tests/wrong_propagate_ret_type.vv:15:17: error: to propagate the Result call, `res_call` must return a Result
-   13 |
+   13 | 
    14 | fn res_call() bool {
    15 |     a := ret_bool()!
       |                    ^
@@ -21,8 +35,15 @@ vlib/v/checker/tests/wrong_propagate_ret_type.vv:15:17: error: to propagate the
    17 | }
 Details: vlib/v/checker/tests/wrong_propagate_ret_type.vv:14:15: details: prepend ! before the declaration of the return type of `res_call`
    12 | }
-   13 |
+   13 | 
    14 | fn res_call() bool {
       |               ~~~~
    15 |     a := ret_bool()!
-   16 |     return a
\ No newline at end of file
+   16 |     return a
+vlib/v/checker/tests/wrong_propagate_ret_type.vv:15:17: error: unexpected `!`, the function `ret_bool` does not return a Result
+   13 | 
+   14 | fn res_call() bool {
+   15 |     a := ret_bool()!
+      |                    ^
+   16 |     return a
+   17 | }
diff --git a/vlib/v/parser/tests/closure_not_declared.out b/vlib/v/parser/tests/closure_not_declared.out
index 093797970c..6dd240a56f 100644
--- a/vlib/v/parser/tests/closure_not_declared.out
+++ b/vlib/v/parser/tests/closure_not_declared.out
@@ -5,3 +5,17 @@ vlib/v/parser/tests/closure_not_declared.vv:4:9: error: `a` must be added to the
       |               ^
     5 |     }
     6 |     f()
+vlib/v/parser/tests/closure_not_declared.vv:4:3: error: `print` can not print void expressions
+    2 |     a := 1
+    3 |     f := fn () {
+    4 |         print(a)
+      |         ~~~~~~~~
+    5 |     }
+    6 |     f()
+vlib/v/parser/tests/closure_not_declared.vv:4:9: error: undefined ident: `a`
+    2 |     a := 1
+    3 |     f := fn () {
+    4 |         print(a)
+      |               ^
+    5 |     }
+    6 |     f()
diff --git a/vlib/v/parser/tests/expected_type_enum_err.out b/vlib/v/parser/tests/expected_type_enum_err.out
index e378cf7d2d..0ca271e2bf 100644
--- a/vlib/v/parser/tests/expected_type_enum_err.out
+++ b/vlib/v/parser/tests/expected_type_enum_err.out
@@ -1,6 +1,12 @@
 vlib/v/parser/tests/expected_type_enum_err.vv:6:12: error: expected type is not an enum (`rune`)
-    4 |
+    4 | 
     5 | fn main() {
     6 |     if `c` == .bar {}
       |               ~~~~
-    7 | }
\ No newline at end of file
+    7 | }
+vlib/v/parser/tests/expected_type_enum_err.vv:6:5: error: non-bool type `void` used as if condition
+    4 | 
+    5 | fn main() {
+    6 |     if `c` == .bar {}
+      |        ~~~~~~~~~~~
+    7 | }
diff --git a/vlib/v/parser/tests/method_call_receiver_err.out b/vlib/v/parser/tests/method_call_receiver_err.out
index 0351a23083..7f54eca232 100644
--- a/vlib/v/parser/tests/method_call_receiver_err.out
+++ b/vlib/v/parser/tests/method_call_receiver_err.out
@@ -19,3 +19,10 @@ vlib/v/parser/tests/method_call_receiver_err.vv:9:11: error: unknown function: S
       |                 ~~~~~~~~~~~~~~~~~~~~~
    10 |     }
    11 | }
+vlib/v/parser/tests/method_call_receiver_err.vv:9:3: error: `println` can not print void expressions
+    7 | 
+    8 |     $for method in S1.methods {
+    9 |         println(S1.method_hello('yo'))
+      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+   10 |     }
+   11 | }
diff --git a/vlib/v/scanner/tests/undefined_ident_in_string_literal_err.out b/vlib/v/scanner/tests/undefined_ident_in_string_literal_err.out
index b6054ac8f0..7d8c72cf60 100644
--- a/vlib/v/scanner/tests/undefined_ident_in_string_literal_err.out
+++ b/vlib/v/scanner/tests/undefined_ident_in_string_literal_err.out
@@ -4,3 +4,9 @@ vlib/v/scanner/tests/undefined_ident_in_string_literal_err.vv:2:15: error: undef
       |                  ~~~~
     3 | }
     4 |
+vlib/v/scanner/tests/undefined_ident_in_string_literal_err.vv:2:15: error: expression does not return a value
+    1 | fn abc() string {
+    2 |     return 'abc $type'
+      |                  ~~~~
+    3 | }
+    4 |
diff --git a/vlib/v/slow_tests/repl/error.repl b/vlib/v/slow_tests/repl/error.repl
index e85d252f99..68136316c4 100644
--- a/vlib/v/slow_tests/repl/error.repl
+++ b/vlib/v/slow_tests/repl/error.repl
@@ -5,3 +5,8 @@ error: undefined ident: `a`
     6 | 
     7 | println(a)
       |         ^
+error: `println` can not print void expressions
+    5 | import math
+    6 | 
+    7 | println(a)
+      | ~~~~~~~~~~
diff --git a/vlib/v/slow_tests/repl/error_and_continue_print.repl b/vlib/v/slow_tests/repl/error_and_continue_print.repl
index 3cfc0bfbf6..253f7f18fe 100644
--- a/vlib/v/slow_tests/repl/error_and_continue_print.repl
+++ b/vlib/v/slow_tests/repl/error_and_continue_print.repl
@@ -7,9 +7,19 @@ error: undefined ident: `a` (use `:=` to declare a variable)
     6 | 
     7 | a = 3
       | ^
+error: cannot assign to `a`: expected `void`, not `int literal`
+    5 | import math
+    6 | 
+    7 | a = 3
+      |     ^
 error: undefined ident: `b`
     5 | import math
     6 | 
     7 | println(b)
       |         ^
+error: `println` can not print void expressions
+    5 | import math
+    6 | 
+    7 | println(b)
+      | ~~~~~~~~~~
 [4]
diff --git a/vlib/v/slow_tests/repl/error_exitasdfasdf.repl b/vlib/v/slow_tests/repl/error_exitasdfasdf.repl
index a026a8ee1a..1ab0f356c2 100644
--- a/vlib/v/slow_tests/repl/error_exitasdfasdf.repl
+++ b/vlib/v/slow_tests/repl/error_exitasdfasdf.repl
@@ -5,3 +5,8 @@ error: undefined ident: `exitasdfasdf`
     6 | 
     7 | println(exitasdfasdf)
       |         ~~~~~~~~~~~~
+error: `println` can not print void expressions
+    5 | import math
+    6 | 
+    7 | println(exitasdfasdf)
+      | ~~~~~~~~~~~~~~~~~~~~~