Refactor types in ssa nodes.

lib/compiler/implementation/ssa/types.dart

 // Copyright (c) 2011, 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.
 
 class SsaTypePropagator extends HGraphVisitor implements OptimizationPhase {
 
   final Map<int, HInstruction> workmap;
   final List<int> worklist;
   final Compiler compiler;
   String get name() => 'type propagator';
@@ skipping 93 matching lines @@
     }
     for (int i = 0, length = instruction.inputs.length; i < length; i++) {
       addToWorkList(instruction.inputs[i]);
     }
   }
 
   HType computeDesiredType(HInstruction instruction) {
     HType desiredType = HType.UNKNOWN;
     for (final user in instruction.usedBy) {
       desiredType =
-          desiredType.combine(user.computeDesiredTypeForInput(instruction));
+          desiredType.intersect(user.computeDesiredTypeForInput(instruction));
       // No need to continue if two users disagree on the type.
       if (desiredType.isConflicting()) break;
     }
     return desiredType;
   }
 
   HType computeType(HInstruction instruction) {
     // Once we are in a conflicting state don't update the type anymore.
     HType oldType = instruction.propagatedType;
     if (oldType.isConflicting()) return oldType;
 
     HType newType = super.computeType(instruction);
     // [computeDesiredType] goes to all usedBys and lets them compute their
     // desired type. By setting the [newType] here we give them more context to
     // work with.
     instruction.propagatedType = newType;
     HType desiredType = computeDesiredType(instruction);
     // If the desired type is conflicting just return the computed type.
     if (desiredType.isConflicting()) return newType;
     // TODO(ngeoffray): Allow speculative optimizations on
     // non-primitive types?
     if (desiredType.isNonPrimitive()) return newType;
-    return newType.combine(desiredType);
+    return newType.intersect(desiredType);
   }
 }