Complain about assignments to parenthesized expressions.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

 // Copyright (c) 2016, 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.
 
 library fasta.body_builder;
 
 import '../parser/parser.dart' show FormalParameterType, optional;
 
 import '../parser/error_kind.dart' show ErrorKind;
 
@@ skipping 470 matching lines @@
           arguments.getRange(firstNamedArgumentIndex, arguments.length));
       push(new Arguments(positional, named: named));
     } else {
       push(new Arguments(arguments));
     }
   }
 
   @override
   void handleParenthesizedExpression(BeginGroupToken token) {
     debugEvent("ParenthesizedExpression");
-    push(popForValue());
+    push(new ParenthesizedExpression(
+        this, popForValue(), token.endGroup.charOffset));
   }
 
   @override
   void endSend(Token beginToken, Token endToken) {
     debugEvent("Send");
     Arguments arguments = pop();
     List<DartType> typeArguments = pop();
     Object receiver = pop();
     if (arguments != null && typeArguments != null) {
       arguments.types.addAll(typeArguments);
@@ skipping 2377 matching lines @@
   } else if (node is PrefixBuilder) {
     return node.name;
   } else if (node is ThisAccessor) {
     return node.isSuper ? "super" : "this";
   } else if (node is FastaAccessor) {
     return node.plainNameForRead;
   } else {
     return internalError("Unhandled: ${node.runtimeType}");
   }
 }