all: make implements work with multiple interfaces

vlib/v/ast/ast.v

@@ -417,8 +417,8 @@ pub:
 	end_comments []Comment
 	embeds       []Embed
 
-	is_implements   bool
-	implements_type Type
+	is_implements    bool
+	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()
@@ -378,24 +383,24 @@ fn (mut p Parser) struct_decl(is_anon bool) ast.StructDecl {
 	}
 	p.expr_mod = ''
 	return ast.StructDecl{
-		name:            name
-		is_pub:          is_pub
-		fields:          ast_fields
-		pos:             start_pos.extend_with_last_line(name_pos, last_line)
-		mut_pos:         mut_pos
-		pub_pos:         pub_pos
-		pub_mut_pos:     pub_mut_pos
-		global_pos:      global_pos
-		module_pos:      module_pos
-		language:        language
-		is_union:        is_union
-		attrs:           if is_anon { []ast.Attr{} } else { attrs } // anon structs can't have attributes
-		pre_comments:    pre_comments
-		end_comments:    end_comments
-		generic_types:   generic_types
-		embeds:          embeds
-		is_implements:   is_implements
-		implements_type: implements_type
+		name:             name
+		is_pub:           is_pub
+		fields:           ast_fields
+		pos:              start_pos.extend_with_last_line(name_pos, last_line)
+		mut_pos:          mut_pos
+		pub_pos:          pub_pos
+		pub_mut_pos:      pub_mut_pos
+		global_pos:       global_pos
+		module_pos:       module_pos
+		language:         language
+		is_union:         is_union
+		attrs:            if is_anon { []ast.Attr{} } else { attrs } // anon structs can't have attributes
+		pre_comments:     pre_comments
+		end_comments:     end_comments
+		generic_types:    generic_types
+		embeds:           embeds
+		is_implements:    is_implements
+		implements_types: implements_types
 	}
 }