Start using the new union/intersection code for HType.INDEXABLE_PRIMITIVE.

sdk/lib/_internal/compiler/implementation/ssa/bailout.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.
 
 part of ssa;
 
 class BailoutInfo {
   int instructionId;
   int bailoutId;
   BailoutInfo(this.instructionId, this.bailoutId);
@@ skipping 114 matching lines @@
       DartType sourceType = source.computeType(compiler);
       DartType speculatedType = speculativeType.computeType(compiler);
       JavaScriptBackend backend = compiler.backend;
       if (speculatedType != null) {
         // Use the num type instead of JSNumber because JSNumber
         // is not assignment compatible with int and double, but we
         // still want to generate a type guard.
         if (speculatedType.element == backend.jsNumberClass) {
           speculatedType = compiler.numClass.computeType(compiler);
         }
+        // Use the JSString type instead of String because String is
+        // not assignment compatible with JSIndexable, but we still
+        // want to generate a type guard.
+        if (sourceType.element == compiler.stringClass) {
+          sourceType = backend.jsStringClass.computeType(compiler);
+        }
         if (!compiler.types.isAssignable(speculatedType, sourceType)) {
           return false;
         }
       }
     }
 
     // Insert type guards for recursive methods.
     if (isRecursiveMethod) return true;
 
     // Insert type guards if there are uses in loops.
@@ skipping 480 matching lines @@
         hasComplexBailoutTargets = true;
       }
     } else {
       hasComplexBailoutTargets = true;
       blocks.forEach((HBasicBlock block) {
         block.bailoutTargets.add(target);
       });
     }
   }
 }