Add support for fields to the new dart backend.

pkg/compiler/lib/src/tree_ir/optimization/copy_propagator.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 tree_ir.optimization;
 
 /// Eliminates moving assignments, such as w := v, by assigning directly to w
 /// at the definition of v.
 ///
 /// This compensates for suboptimal register allocation, and merges closure
 /// variables with local temporaries that were left behind when translating
 /// out of CPS (where closure variables live in a separate space).
-class CopyPropagator extends RecursiveVisitor implements Pass {
+class CopyPropagator extends RecursiveVisitor with PassMixin {
 
   /// After visitStatement returns, [move] maps a variable v to an
   /// assignment A of form w := v, under the following conditions:
   /// - there are no uses of w before A
   /// - A is the only use of v
   Map<Variable, Assign> move = <Variable, Assign>{};
 
   /// Like [move], except w is the key instead of v.
   Map<Variable, Assign> inverseMove = <Variable, Assign>{};
 
-  /// The function currently being rewritten.
-  FunctionElement functionElement;
+  ExecutableElement currentElement;
 
-  void rewrite(FunctionDefinition function) {
-    if (function.isAbstract) return;
-
-    functionElement = function.element;
-    visitFunctionDefinition(function);
+  void rewriteExecutableDefinition(ExecutableDefinition root) {
+    currentElement = root.element;
+    root.body = visitStatement(root.body);
   }
 
-  void visitFunctionDefinition(FunctionDefinition function) {
-    assert(functionElement == function.element);
-    function.body = visitStatement(function.body);
+  rewriteFunctionDefinition(FunctionDefinition function) {
+    if (function.isAbstract) return;
+    rewriteExecutableDefinition(function);
 
     // Try to propagate moving assignments into function parameters.
     // For example:
     // foo(x) {
     //   var v1 = x;
     //   BODY
     // }
     //   ==>
     // foo(v1) {
     //   BODY
     // }
 
     // Variables must not occur more than once in the parameter list, so
     // invalidate all moving assignments that would propagate a parameter
     // into another parameter. For example:
     // foo(x,y) {
     //   y = x;
     //   BODY
     // }
     // Cannot declare function as foo(x,x)!
     function.parameters.forEach(visitVariable);
 
     // Now do the propagation.
-    for (int i=0; i<function.parameters.length; i++) {
+    for (int i = 0; i < function.parameters.length; i++) {
       Variable param = function.parameters[i];
       Variable replacement = copyPropagateVariable(param);
       replacement.element = param.element; // Preserve parameter name.
       function.parameters[i] = replacement;
     }
   }
 
   Statement visitBasicBlock(Statement node) {
     node = visitStatement(node);
     move.clear();
@@ skipping 53 matching lines @@
     node.variable = copyPropagateVariable(node.variable);
     visitExpression(node.definition);
     visitVariable(node.variable);
 
     // If this is a moving assignment w := v, with this being the only use of v,
     // try to propagate it backwards.  Do not propagate assignments where w
     // is from an outer function scope.
     if (node.definition is Variable) {
       Variable def = node.definition;
       if (def.readCount == 1 &&
-          node.variable.host.element == functionElement) {
+          node.variable.host == currentElement) {
         move[node.definition] = node;
         inverseMove[node.variable] = node;
       }
     }
 
     return node;
   }
 
   Statement visitLabeledStatement(LabeledStatement node) {
     node.next = visitBasicBlock(node.next);
@@ skipping 42 matching lines @@
     node.next = visitStatement(node.next);
     visitExpression(node.expression);
     return node;
   }
 
   void visitFunctionExpression(FunctionExpression node) {
     new CopyPropagator().rewrite(node.definition);
   }
 
 }