Don't constant fold operation if result is incompatible with it.

runtime/vm/compiler.cc

 // 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.
 
 #include "vm/compiler.h"
 
 #include "vm/assembler.h"
 
 #include "vm/ast_printer.h"
 #include "vm/block_scheduler.h"
@@ skipping 639 matching lines @@
             (flow_graph->graph_entry()->SuccessorCount()  == 1)) {
           // TODO(fschneider): Support allocation sinking with try-catch.
           sinking = new AllocationSinking(flow_graph);
           sinking->Optimize();
         }
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
 
         DeadCodeElimination::EliminateDeadPhis(flow_graph);
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
 
+        FlowGraphTypePropagator::Propagate(flow_graph);
+        DEBUG_ASSERT(flow_graph->VerifyUseLists());
+
         // Ensure that all phis inserted by optimization passes have consistent
         // representations.
         optimizer.SelectRepresentations();
 
         if (optimizer.Canonicalize()) {
           // To fully remove redundant boxing (e.g. BoxDouble used only in
           // environments and UnboxDouble instructions) instruction we
           // first need to replace all their uses and then fold them away.
           // For now we just repeat Canonicalize twice to do that.
           // TODO(vegorov): implement a separate representation folding pass.
@@ skipping 552 matching lines @@
     const Object& result =
       PassiveObject::Handle(isolate->object_store()->sticky_error());
     isolate->object_store()->clear_sticky_error();
     return result.raw();
   }
   UNREACHABLE();
   return Object::null();
 }
 
 }  // namespace dart