Refactor types in ssa nodes.

lib/compiler/implementation/ssa/optimize.dart

Index: lib/compiler/implementation/ssa/optimize.dart
diff --git a/lib/compiler/implementation/ssa/optimize.dart b/lib/compiler/implementation/ssa/optimize.dart
index a1562b535c79efae6f852115688d6281c8b531fc..9057f92d3d9555225197822f44a1e0d380972ee1 100644
--- a/lib/compiler/implementation/ssa/optimize.dart
+++ b/lib/compiler/implementation/ssa/optimize.dart
@@ -289,7 +289,7 @@ class SsaConstantFolder extends HBaseVisitor implements OptimizationPhase {
 
   HInstruction visitTypeGuard(HTypeGuard node) {
     HInstruction value = node.guarded;
-    HType combinedType = value.propagatedType.combine(node.guardedType);
+    HType combinedType = value.propagatedType.intersect(node.guardedType);
     return (combinedType == value.propagatedType) ? value : node;
   }
 
@@ -403,7 +403,7 @@ class SsaCheckInserter extends HBaseVisitor implements OptimizationPhase {
   }
 
   void visitIndex(HIndex node) {
-    if (!node.receiver.isStringOrArray()) return;
+    if (!node.receiver.isIndexablePrimitive()) return;
     HInstruction index = node.index;
     if (index is HBoundsCheck) return;
     if (!node.index.isInteger()) {