parser: support bool values in attributes (#12750)

vlib/v/ast/attr.v

@@ -9,6 +9,7 @@ pub enum AttrKind {
 	plain // [name]
 	string // ['name']
 	number // [123]
+	bool // [true] || [false]
 	comptime_define // [if name]
 }
 
@@ -41,7 +42,7 @@ pub fn (a Attr) str() string {
 		a.name
 	}
 	s += match a.kind {
-		.plain, .number { arg }
+		.plain, .number, .bool { arg }
 		.string { "'$arg'" }
 		.comptime_define { 'if $arg' }
 	}

vlib/v/parser/parser.v

@@ -1596,11 +1596,10 @@ fn (mut p Parser) parse_attr() ast.Attr {
 		if p.tok.kind == .colon {
 			has_arg = true
 			p.next()
-			// `name: arg`
-			if p.tok.kind == .name {
+			if p.tok.kind == .name { // `name: arg`
 				kind = .plain
 				arg = p.check_name()
-			} else if p.tok.kind == .number {
+			} else if p.tok.kind == .number { // `name: 123`
 				kind = .number
 				arg = p.tok.lit
 				p.next()
@@ -1608,6 +1607,10 @@ fn (mut p Parser) parse_attr() ast.Attr {
 				kind = .string
 				arg = p.tok.lit
 				p.next()
+			} else if p.tok.kind == .key_true || p.tok.kind == .key_false { // `name: true`
+				kind = .bool
+				arg = p.tok.kind.str()
+				p.next()
 			} else {
 				p.error('unexpected $p.tok, an argument is expected after `:`')
 			}

vlib/v/tests/attribute_test.v

@@ -10,6 +10,12 @@ pub struct PubStructAttrTest {
 	bar int
 }
 
+struct StructFieldAttrTest {
+	foo string [attr: bar; attr0; attr1: 'foo']
+	bar int    [attr0: 123; attr1: true; attr2: false]
+	baz bool   [prefix.attr0] = false
+}
+
 [testing]
 enum EnumAttrTest {
 	one