Fix some warnings.

lib/compiler/implementation/ssa/optimize.dart

 // Copyright (c) 2012, 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.
 
 abstract class OptimizationPhase {
   String get name;
   void visitGraph(HGraph graph);
 }
 
 class SsaOptimizerTask extends CompilerTask {
@@ skipping 185 matching lines @@
       Constant folded = operation.fold(receiver.constant);
       if (folded !== null) return graph.addConstant(folded);
     }
     return node;
   }
 
   HInstruction visitInvokeInterceptor(HInvokeInterceptor node) {
     // Try to recognize the length interceptor with input [:new List(int):].
     if (node.isLengthGetter() && node.inputs[1] is HInvokeStatic) {
       HInvokeStatic call = node.inputs[1];
-      Element element = call.inputs[0].element;
+      Element element = call.target.element;
       if (element.isConstructor() &&
           element.enclosingElement == compiler.listClass.defaultClass.element) {
         if (call.inputs.length == 2 && call.inputs[1].isInteger(types)) {
           return call.inputs[1];
         }
       }
     }
     HInstruction input = node.inputs[1];
     if (node.isLengthGetter()) {
       if (input.isConstantString()) {
@@ skipping 1105 matching lines @@
     }
 
     // For other fields having setters in the generative constructor body, set
     // the type to UNKNOWN to avoid relying on the type set in the initializer
     // list.
     allSetters.forEach((Element element) {
       backend.registerFieldConstructor(element, HType.UNKNOWN);
     });
   }
 }