Properly parse operator declarations without return type.

tests/compiler/dart2js/parser_test.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #import('parser_helper.dart');
 #import("../../../lib/compiler/implementation/tree/tree.dart");
 
 void testStatement(String statement) {
   Node node = parseStatement(statement);
   Expect.isNotNull(node.toString());
@@ skipping 236 matching lines @@
   node = parseStatement("a.b++;");
   // Should parse as: (a.b)++.
   expression = node.expression;
   Expect.isNotNull(sendSet = expression.asSendSet());
   Expect.stringEquals("a", sendSet.receiver.toString());
   Expect.stringEquals("b", sendSet.selector.toString());
   Expect.stringEquals("++", sendSet.assignmentOperator.toString());
   Expect.isTrue(sendSet.arguments.isEmpty());
 }
 
+void testOperatorParse() {
+  FunctionDeclaration node = parseStatement('operator negate() => null;');
+  FunctionExpression function = node.function;
+  Send name = function.name.asSend();
+  Expect.isNotNull(name);
+  Expect.stringEquals('operator', name.receiver.source.stringValue);
+  Expect.stringEquals('negate', name.selector.source.stringValue);
+  Expect.isTrue(function.parameters.isEmpty());
+  Expect.isNull(function.returnType);
+  Expect.isNull(function.getOrSet);
+}
+
 void main() {
   testGenericTypes();
   // TODO(ahe): Enable this test when we handle library prefixes.
   // testPrefixedGenericTypes();
   testUnaryExpression();
   testChainedMethodCalls();
   testFunctionStatement();
   testDoStatement();
   testWhileStatement();
   testConditionalExpression();
   testAssignment();
   testIndex();
   testPostfix();
+  testOperatorParse();
 }