Emit a compile-time error when the name of a variable is referenced in the

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

Index: sdk/lib/_internal/compiler/implementation/resolution/scope.dart
diff --git a/sdk/lib/_internal/compiler/implementation/resolution/scope.dart b/sdk/lib/_internal/compiler/implementation/resolution/scope.dart
index 0af9fd78b325db9e25abd819366a322b2e4fb601..81eadaebbfd52814cf78aa4811fd73e8ee023b46 100644
--- a/sdk/lib/_internal/compiler/implementation/resolution/scope.dart
+++ b/sdk/lib/_internal/compiler/implementation/resolution/scope.dart
@@ -41,6 +41,24 @@ abstract class NestedScope extends Scope {
   }
 }
 
+class VariableDefinitionScope extends NestedScope {
+  final SourceString variableName;
+  bool variableReferencedInInitializer = false;
+
+  VariableDefinitionScope(Scope parent, this.variableName) : super(parent);
+
+  Element localLookup(SourceString name) {
+    if (name == variableName) {
+      variableReferencedInInitializer = true;
+    }
+    return null;
+  }
+
+  Element add(Element newElement) {
+    throw "Cannot add element to VariableDefinitionScope";
+  }
+}
+
 /**
  * [TypeDeclarationScope] defines the outer scope of a type declaration in
  * which the declared type variables and the entities in the enclosing scope are