From e4ffc7f224f58e473045e8261f7c73f7d9fb11f1 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Thu, 17 Oct 2024 05:50:10 -0300
Subject: [PATCH] v: add support for `T.unaliased_typ`  (#22546)

---
 vlib/v/ast/ast.v                              |  1 +
 vlib/v/checker/checker.v                      |  3 ++
 vlib/v/gen/c/cgen.v                           |  4 +++
 vlib/v/gen/c/comptime.v                       |  2 ++
 vlib/v/gen/js/js.v                            |  8 ++++-
 vlib/v/parser/parser.v                        |  1 +
 .../comptime_generic_unaliased_typ_test.v     | 35 +++++++++++++++++++
 7 files changed, 53 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/tests/comptime/comptime_generic_unaliased_typ_test.v

diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index c8cd71cf56..03e94d1ca3 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -279,6 +279,7 @@ pub enum GenericKindField {
 	unknown
 	name
 	typ
+	unaliased_typ
 }
 
 // `foo.bar`
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 62be8f886c..507155b630 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1513,6 +1513,9 @@ fn (mut c Checker) selector_expr(mut node ast.SelectorExpr) ast.Type {
 			.name {
 				return ast.string_type
 			}
+			.unaliased_typ {
+				return ast.int_type
+			}
 			.typ {
 				return ast.int_type
 			}
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index b55d570323..6f24e11518 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -3880,6 +3880,10 @@ fn (mut g Gen) selector_expr(node ast.SelectorExpr) {
 				g.write(int(g.unwrap_generic(node.name_type)).str())
 				return
 			}
+			.unaliased_typ {
+				g.write(int(g.table.unaliased_type(g.unwrap_generic(node.name_type))).str())
+				return
+			}
 			.unknown {
 				// ast.TypeOf of `typeof(string).idx` etc
 				if node.field_name == 'name' {
diff --git a/vlib/v/gen/c/comptime.v b/vlib/v/gen/c/comptime.v
index 84b54ac884..579c7cac66 100644
--- a/vlib/v/gen/c/comptime.v
+++ b/vlib/v/gen/c/comptime.v
@@ -473,6 +473,8 @@ fn (mut g Gen) get_expr_type(cond ast.Expr) ast.Type {
 		ast.SelectorExpr {
 			if cond.gkind_field == .typ {
 				return g.unwrap_generic(cond.name_type)
+			} else if cond.gkind_field == .unaliased_typ {
+				return g.table.unaliased_type(g.unwrap_generic(cond.name_type))
 			} else {
 				name := '${cond.expr}.${cond.field_name}'
 				if name in g.comptime.type_map {
diff --git a/vlib/v/gen/js/js.v b/vlib/v/gen/js/js.v
index 5803c9f020..4bd9e4ea26 100644
--- a/vlib/v/gen/js/js.v
+++ b/vlib/v/gen/js/js.v
@@ -3250,12 +3250,18 @@ fn (mut g JsGen) gen_selector_expr(it ast.SelectorExpr) {
 			}
 			.typ {
 				g.write('new int(')
-
 				g.write('${int(g.unwrap_generic(it.name_type))}')
 				g.write(')')
 				g.write(')')
 				return
 			}
+			.unaliased_typ {
+				g.write('new int(')
+				g.write('${int(g.table.unaliased_type(g.unwrap_generic(it.name_type)))}')
+				g.write(')')
+				g.write(')')
+				return
+			}
 			.unknown {
 				if node.field_name == 'name' {
 					g.type_name(it.name_type)
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 4f9880040c..0b29ffd40c 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -2936,6 +2936,7 @@ fn (mut p Parser) name_expr() ast.Expr {
 			fkind := match field {
 				'name' { ast.GenericKindField.name }
 				'typ' { ast.GenericKindField.typ }
+				'unaliased_typ' { ast.GenericKindField.unaliased_typ }
 				else { ast.GenericKindField.unknown }
 			}
 			pos.extend(p.tok.pos())
diff --git a/vlib/v/tests/comptime/comptime_generic_unaliased_typ_test.v b/vlib/v/tests/comptime/comptime_generic_unaliased_typ_test.v
new file mode 100644
index 0000000000..c2c82a9b2b
--- /dev/null
+++ b/vlib/v/tests/comptime/comptime_generic_unaliased_typ_test.v
@@ -0,0 +1,35 @@
+struct Struct {
+	a int
+}
+
+type StructAlias = Struct
+
+fn test_main() {
+	mut a := StructAlias(Struct{})
+	assert alias_first(a) == 'alias'
+	assert struct_first(a) == 'struct'
+}
+
+fn alias_first[T](val T) string {
+	$if T is $alias {
+		return 'alias'
+	} $else $if T is $struct {
+		return 'struct'
+	} $else {
+		return 'else'
+	}
+}
+
+fn struct_first[T](val T) string {
+	$if T is $struct {
+		return 'struct'
+	} $else $if T is $alias {
+		$if T.unaliased_typ is $struct {
+			return 'struct'
+		} $else {
+			return 'alias'
+		}
+	} $else {
+		return 'else'
+	}
+}