Special scope for labelled statements.

pkg/front_end/lib/src/fasta/scope.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.scope;
 
 import 'builder/builder.dart' show Builder, MixedAccessor;
 
 import 'errors.dart' show internalError;
 
@@ skipping 28 matching lines @@
       : this(const <String, Builder>{}, const <String, Builder>{}, null,
             isModifiable: false);
 
   Scope.nested(Scope parent, {bool isModifiable: true})
       : this(<String, Builder>{}, null, parent, isModifiable: isModifiable);
 
   Scope createNestedScope({bool isModifiable: true}) {
     return new Scope.nested(this, isModifiable: isModifiable);
   }
 
+  /// Create a special scope for use by labeled staments. This scope doesn't
+  /// introduce a new scope for local variables, only for labels. This deals
+  /// with corner cases like this:
+  ///
+  ///     L: var x;
+  ///     x = 42;
+  ///     print("The answer is $x.");
+  Scope createNestedLabelScope() {
+    return new Scope(local, setters, parent, isModifiable: true);
+  }
+
   Builder lookup(String name, int charOffset, Uri fileUri,
       {bool isInstanceScope: true}) {
     Builder builder = local[name];
     if (builder != null) {
       if (builder.next != null) {
         return lookupAmbiguous(name, builder, false, charOffset, fileUri);
       }
       return builder.isSetter
           ? new AccessErrorBuilder(name, builder, charOffset, fileUri)
           : builder;
@@ skipping 144 matching lines @@
 
   String get message => "Access error: '$name'.";
 }
 
 class AmbiguousBuilder extends ProblemBuilder {
   AmbiguousBuilder(String name, Builder builder, int charOffset, Uri fileUri)
       : super(name, builder, charOffset, fileUri);
 
   String get message => "Duplicated named: '$name'.";
 }