problems parsing guard with two not (#376)

Author: aeschli

src/parser/cssNodes.ts

@@ -1795,7 +1795,6 @@ export class ListEntry extends Node {
 
 export class LessGuard extends Node {
 
-	public isNegated?: boolean;
 	private conditions?: Nodelist;
 
 	public getConditions(): Nodelist {
@@ -1808,6 +1807,7 @@ export class LessGuard extends Node {
 
 export class GuardCondition extends Node {
 
+	public isNegated?: boolean;
 	public variable?: Node;
 	public isEquals?: boolean;
 	public isGreater?: boolean;

src/parser/lessParser.ts

@@ -730,7 +730,6 @@ export class LESSParser extends cssParser.Parser {
 		}
 		const node = <nodes.LessGuard>this.create(nodes.LessGuard);
 		this.consumeToken(); // when
-		node.isNegated = this.acceptIdent('not');
 
 		if (!node.getConditions().addChild(this._parseGuardCondition())) {
 			return <nodes.LessGuard>this.finish(node, ParseError.ConditionExpected);
@@ -745,12 +744,14 @@ export class LESSParser extends cssParser.Parser {
 	}
 
 	public _parseGuardCondition(): nodes.Node | null {
-
-		if (!this.peek(TokenType.ParenthesisL)) {
+		const node = this.create(nodes.GuardCondition);
+		node.isNegated = this.acceptIdent('not');
+		if (!this.accept(TokenType.ParenthesisL)) {
+			if (node.isNegated) {
+				return this.finish(node, ParseError.LeftParenthesisExpected);
+			}
 			return null;
 		}
-		const node = this.create(nodes.GuardCondition);
-		this.consumeToken(); // ParenthesisL
 
 		if (!node.addChild(this._parseExpr())) {
 			// empty (?)

src/test/less/parser.test.ts

@@ -313,6 +313,7 @@ suite('LESS - Parser', () => {
 
 	test('CSS Guards', function () {
 		const parser = new LESSParser();
+		assertNode('.selector when not ( @testCondition = 2) and not ( @testCondition = 3 ) { }', parser, parser._parseStylesheet.bind(parser));
 		assertNode('button when (@my-option = true) { color: white; }', parser, parser._parseStylesheet.bind(parser));
 		assertNode('.something .other when (@my-option = true) { color: white; }', parser, parser._parseStylesheet.bind(parser));
 		assertNode('& when (@my-option = true) { button { color: white; } }', parser, parser._parseStylesheet.bind(parser));