Improve parser error recovery.

dart/sdk/lib/_internal/compiler/implementation/resolution/signatures.dart

 // Copyright (c) 2014, 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.
 
 part of resolution;
 
 /**
  * [SignatureResolver] resolves function signatures.
  */
 class SignatureResolver extends MappingVisitor<ParameterElementX> {
@@ skipping 234 matching lines @@
                                    Node returnNode,
                                    Element element,
                                    ResolutionRegistry registry,
                                    {MessageKind defaultValuesError}) {
     SignatureResolver visitor = new SignatureResolver(compiler, element,
         registry, defaultValuesError: defaultValuesError);
     Link<Element> parameters = const Link<Element>();
     int requiredParameterCount = 0;
     if (formalParameters == null) {
       if (!element.isGetter) {
-        compiler.reportError(element, MessageKind.MISSING_FORMALS);
+        if (element.isErroneous) {
+          // If the element is erroneous, an error should already have been
+          // reported. In the case of parse errors, it is possible that there
+          // are formal parameters, but something else in the method failed to
+          // parse. So we suppress the message about missing formals.
+          assert(invariant(element, compiler.compilationFailed));
+        } else {
+          compiler.reportError(element, MessageKind.MISSING_FORMALS);
+        }
       }
     } else {
       if (element.isGetter) {
         if (!identical(formalParameters.endToken.next.stringValue,
                        // TODO(ahe): Remove the check for native keyword.
                        'native')) {
           compiler.reportError(formalParameters,
                                MessageKind.EXTRA_FORMALS);
         }
       }
@@ skipping 78 matching lines @@
 
   DartType resolveReturnType(TypeAnnotation annotation) {
     if (annotation == null) return const DynamicType();
     DartType result = resolver.resolveTypeAnnotation(annotation);
     if (result == null) {
       return const DynamicType();
     }
     return result;
   }
 }