Refactor types in ssa nodes.

lib/compiler/implementation/ssa/types.dart

Index: lib/compiler/implementation/ssa/types.dart
diff --git a/lib/compiler/implementation/ssa/types.dart b/lib/compiler/implementation/ssa/types.dart
index 0f12bb9e8e1b3d6998147afeddea202411b5822c..1d243ff65b69004c930512a2e57938778e1fa7e2 100644
--- a/lib/compiler/implementation/ssa/types.dart
+++ b/lib/compiler/implementation/ssa/types.dart
@@ -111,7 +111,7 @@ class SsaSpeculativeTypePropagator extends SsaTypePropagator {
     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;
     }
@@ -134,6 +134,6 @@ class SsaSpeculativeTypePropagator extends SsaTypePropagator {
     // TODO(ngeoffray): Allow speculative optimizations on
     // non-primitive types?
     if (desiredType.isNonPrimitive()) return newType;
-    return newType.combine(desiredType);
+    return newType.intersect(desiredType);
   }
 }