refactor parse step

src/compiler/parse/state/tag.ts

@@ -192,8 +192,9 @@ export default function tag(parser: Parser) {
 		}
 
 		const definition = element.attributes.splice(index, 1)[0];
-		if (definition.value === true || definition.value.length !== 1 ||
-			(definition.value[0].type !== 'Text' && definition.value[0].type !== 'MustacheTag' && definition.value[0].type !== 'AttributeShorthand')) {
+		if (definition.value === true
+			|| definition.value.length !== 1
+			|| !['Text', 'MustacheTag', 'AttributeShorthand'].includes(definition.value[0].type)) {
 			parser.error(parser_errors.invalid_element_definition, definition.start);
 		}