Prepare for separate setter scope.

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;
 
 class Scope {
   /// Names declared in this scope.
   final Map<String, Builder> local;
 
+  /// Setters declared in this scope.
+  final Map<String, Builder> setters;
+
   /// The scope that this scope is nested within, or `null` if this is the top
   /// level scope.
   final Scope parent;
 
   /// Indicates whether an attempt to declare new names in this scope should
   /// succeed.
   final bool isModifiable;
 
   Map<String, Builder> labels;
 
   Map<String, Builder> forwardDeclaredLabels;
 
-  Scope(this.local, this.parent, {this.isModifiable: true});
+  Scope(this.local, Map<String, Builder> setters, this.parent,
+      {this.isModifiable: true})
+      : setters = setters ?? const <String, Builder>{};
+
+  Scope.top({bool isModifiable: false})
+      : this(<String, Builder>{}, <String, Builder>{}, null,
+            isModifiable: isModifiable);
+
+  Scope.immutable()
+      : 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(<String, Builder>{}, this, isModifiable: isModifiable);
+    return new Scope.nested(this, isModifiable: isModifiable);
   }
 
-  Builder lookup(String name, int charOffset, Uri fileUri) {
+  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;
     } else {
       return parent?.lookup(name, charOffset, fileUri);
     }
   }
 
-  Builder lookupSetter(String name, int charOffset, Uri fileUri) {
+  Builder lookupSetter(String name, int charOffset, Uri fileUri,
+      {bool isInstanceScope: true}) {
     Builder builder = local[name];
     if (builder != null) {
       if (builder.next != null) {
         return lookupAmbiguous(name, builder, true, charOffset, fileUri);
       }
       if (builder.isField) {
         if (builder.isFinal) {
           return new AccessErrorBuilder(name, builder, charOffset, fileUri);
         } else {
           return builder;
@@ skipping 66 matching lines @@
   }
 
   // TODO(ahe): Rename to extend or something.
   void operator []=(String name, Builder member) {
     if (isModifiable) {
       local[name] = member;
     } else {
       internalError("Can't extend an unmodifiable scope.");
     }
   }
+
+  void forEach(f(String name, Builder member)) {
+    local.forEach(f);
+  }
 }
 
 abstract class ProblemBuilder extends Builder {
   final String name;
 
   final Builder builder;
 
   ProblemBuilder(this.name, this.builder, int charOffset, Uri fileUri)
       : super(null, charOffset, fileUri);
 
@@ skipping 37 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'.";
 }