Fix some warnings.

lib/compiler/implementation/ssa/value_range_analyzer.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.
 
 /**
  * A [Value] represents both symbolic values like the value of a
  * parameter, or the length of an array, and concrete values, like
  * constants.
  */
 abstract class Value {
@@ skipping 171 matching lines @@
   String toString() => 'Length: $instruction';
 }
 
 /**
  * Represents a binary operation on two [Value], where the operation
  * did not yield a canonical value.
  */
 class OperationValue extends Value {
   final Value left;
   final Value right;
-  final Operation operation;
+  final BinaryOperation operation;
   OperationValue(this.left, this.right, this.operation);
 
   bool operator ==(other) {
     if (other is !OperationValue) return false;
     return left == other.left
         && right == other.right
         && operation == other.operation;
   }
 
   Value operator +(Value other) => const UnknownValue();
@@ skipping 188 matching lines @@
     return range;
   }
 
   Range tryInferLoopPhiRange(HPhi phi) {
     HInstruction update = phi.inputs[1];
     return update.accept(new LoopUpdateRecognizer(phi, ranges, types));
   }
 
   Range visitConstant(HConstant constant) {
     if (!constant.isInteger(types)) return const Range.unbound();
-    Value value = new IntValue(constant.constant.value);
+    IntConstant constantInt = constant.constant;
+    Value value = new IntValue(constantInt.value);
     return new Range(value, value);
   }
 
   Range visitInvokeInterceptor(HInvokeInterceptor interceptor) {
     if (!interceptor.isInteger(types)) return const Range.unbound();
     if (!interceptor.isLengthGetterOnStringOrArray(types)) {
       return visitInstruction(interceptor);
     }
     LengthValue value = new LengthValue(interceptor);
     // We know this range is above zero. To simplify the analysis, we
@@ skipping 267 matching lines @@
     if (instruction is HPhi && !instruction.block.isLoopHeader()) {
       HInstruction result = unwrap(instruction.inputs[0]);
       for (int i = 1; i < instruction.inputs.length; i++) {
         if (result != unwrap(instruction.inputs[i])) return instruction;
       }
       return result;
     }
     return instruction;
   }
 }