Support assignment to parameters in the dart2dart backend.

sdk/lib/_internal/compiler/implementation/ir/ir_builder.dart

 // Copyright (c) 2013, 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 dart2js.ir_builder;
 
 import 'ir_nodes.dart' as ir;
 import '../elements/elements.dart';
 import '../dart2jslib.dart';
 import '../dart_types.dart';
@@ skipping 333 matching lines @@
   ir.Definition visitClosureSend(ast.Send node) {
     return giveup();
   }
 
   ir.Definition visitDynamicSend(ast.Send node) {
     return giveup();
   }
 
   ir.Definition visitGetterSend(ast.Send node) {
     Element element = elements[node];
-    if ((element != null && element.isForeign(compiler))
-        || Elements.isStaticOrTopLevelField(element)
-        || Elements.isInstanceSend(node, elements)
-        || Elements.isStaticOrTopLevelFunction(element)
-        || Elements.isErroneousElement(element)) {
-      return giveup();
-    }
+    if (!Elements.isLocal(element)) return giveup();
     return assignedVars[variableIndex[element]];
   }
 
   ir.Definition visitOperatorSend(ast.Send node) {
     return giveup();
   }
 
   // Build(StaticSend(f, arguments), C) = C[C'[InvokeStatic(f, xs)]]
   //   where (C', xs) = arguments.fold(Build, C)
   ir.Definition visitStaticSend(ast.Send node) {
@@ skipping 42 matching lines @@
   }
 
   ir.Definition visitSuperSend(ast.Send node) {
     return giveup();
   }
 
   ir.Definition visitTypeReferenceSend(ast.Send node) {
     return giveup();
   }
 
+  ir.Definition visitSendSet(ast.SendSet node) {
+    Element element = elements[node];
+    if (!Elements.isLocal(element)) return giveup();
+    if (node.assignmentOperator.source != '=') return giveup();
+    // Exactly one argument expected for a simple assignment.
+    assert(!node.arguments.isEmpty && node.arguments.tail.isEmpty);
+    ir.Definition result = node.arguments.head.accept(this);
+    assignedVars[variableIndex[element]] = result;
+    return result;
+  }
+
   static final String ABORT_IRNODE_BUILDER = "IrNode builder aborted";
 
   ir.Definition giveup() => throw ABORT_IRNODE_BUILDER;
 
   ir.FunctionDefinition nullIfGiveup(ir.FunctionDefinition action()) {
     try {
       return action();
     } catch(e) {
       if (e == ABORT_IRNODE_BUILDER) return null;
       rethrow;
     }
   }
 
   void internalError(String reason, {ast.Node node}) {
     giveup();
   }
 }
 
 // Verify that types are ones that can be reconstructed by the type emitter.
 class SupportedTypeVerifier extends DartTypeVisitor<bool, Null> {
   bool visitType(DartType type, Null _) => false;
 
   bool visitVoidType(VoidType type, Null _) => true;
 
   // Currently, InterfaceType and TypedefType are supported so long as they
   // do not have type parameters.  They are subclasses of GenericType.
   bool visitGenericType(GenericType type, Null _) => !type.isGeneric;
 }