all: make implements work with multiple interfaces

vlib/v/ast/ast.v

@@ -418,7 +418,7 @@ pub:
 	embeds       []Embed
 
 	is_implements    bool
-	implements_type Type
+	implements_types []Type
 pub mut:
 	fields []StructField
 }

vlib/v/checker/struct.v

@@ -333,7 +333,9 @@ fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 		// XTODO2
 		// cgen error if I use `println(sym)` without handling the option with `or{}`
 		struct_type := c.table.find_type_idx(node.name) // or { panic(err) }
-		c.type_implements(struct_type, node.implements_type, node.pos)
+		for t in node.implements_types {
+			c.type_implements(struct_type, t, node.pos)
+		}
 	}
 }
 

vlib/v/checker/tests/implements_keyword.out

@@ -5,3 +5,17 @@ vlib/v/checker/tests/implements_keyword.vv:5:1: error: `CustomError` doesn't imp
       | ~~~~~~~~~~~~~~~~~~
     6 | }
     7 |
+vlib/v/checker/tests/implements_keyword.vv:15:1: error: `CustomError2` doesn't implement method `print_error` of interface `MyError`
+   13 | }
+   14 |
+   15 | struct CustomError2 implements MyError, MyError2 {
+      | ~~~~~~~~~~~~~~~~~~~
+   16 | }
+   17 |
+vlib/v/checker/tests/implements_keyword.vv:15:1: error: `CustomError2` doesn't implement method `print_error2` of interface `MyError2`
+   13 | }
+   14 |
+   15 | struct CustomError2 implements MyError, MyError2 {
+      | ~~~~~~~~~~~~~~~~~~~
+   16 | }
+   17 |

vlib/v/checker/tests/implements_keyword.vv

@@ -7,3 +7,13 @@ struct CustomError implements MyError {
 
 fn (e CustomError) print_error2() {
 }
+
+interface MyError2 {
+	print_error2()
+}
+
+struct CustomError2 implements MyError, MyError2 {
+}
+
+fn (e CustomError2) print_error3() {
+}

vlib/v/fmt/struct.v

@@ -33,7 +33,12 @@ pub fn (mut f Fmt) struct_decl(node ast.StructDecl, is_anon bool) {
 	mut field_types := []string{cap: node.fields.len}
 	if node.is_implements {
 		f.write(' implements ')
-		f.write(f.table.type_to_str_using_aliases(node.implements_type, f.mod2alias))
+		for i, t in node.implements_types {
+			f.write(f.table.type_to_str_using_aliases(t, f.mod2alias))
+			if i < node.implements_types.len - 1 {
+				f.write(', ')
+			}
+		}
 	}
 	// Calculate the alignments first
 	f.calculate_alignment(node.fields, mut type_align, mut comment_align, mut default_expr_align, mut

vlib/v/parser/struct.v

@@ -94,14 +94,19 @@ fn (mut p Parser) struct_decl(is_anon bool) ast.StructDecl {
 	mut is_field_pub := false
 	mut is_field_global := false
 	mut is_implements := false
-	mut implements_type := ast.void_type
+	mut implements_types := []ast.Type{cap: 3} // ast.void_type
 	mut last_line := p.prev_tok.pos().line_nr + 1
 	mut end_comments := []ast.Comment{}
 	if !no_body {
 		if p.tok.kind == .key_implements {
-			p.next()
-			implements_type = p.parse_type()
 			is_implements = true
+			for {
+				p.next()
+				implements_types << p.parse_type()
+				if p.tok.kind != .comma {
+					break
+				}
+			}
 		}
 		p.check(.lcbr)
 		pre_comments << p.eat_comments()
@@ -395,7 +400,7 @@ fn (mut p Parser) struct_decl(is_anon bool) ast.StructDecl {
 		generic_types:    generic_types
 		embeds:           embeds
 		is_implements:    is_implements
-		implements_type: implements_type
+		implements_types: implements_types
 	}
 }