[strong] Disallow implicit conversions for binary arithmetic operations

src/compiler/js-typed-lowering.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/access-builder.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 #include "src/compiler/operator-properties.h"
@@ skipping 326 matching lines @@
     return r.ChangeToPureOperator(simplified()->StringAdd());
   }
 #endif
   return NoChange();
 }
 
 
 Reduction JSTypedLowering::ReduceNumberBinop(Node* node,
                                              const Operator* numberOp) {
   JSBinopReduction r(this, node);
+  if (is_strong(OpParameter<LanguageMode>(node))) {
+    if (r.left_type()->Is(Type::Number()) &&
+        (r.right_type()->Is(Type::Number()))) {
+      return r.ChangeToPureOperator(numberOp, Type::Number());
+    }
+    return NoChange();
+  }
   Node* frame_state = NodeProperties::GetFrameStateInput(node, 1);
   r.ConvertInputsToNumber(frame_state);
   return r.ChangeToPureOperator(numberOp, Type::Number());
 }
 
 
 Reduction JSTypedLowering::ReduceInt32Binop(Node* node, const Operator* intOp) {
   JSBinopReduction r(this, node);
   Node* frame_state = NodeProperties::GetFrameStateInput(node, 1);
   r.ConvertInputsToNumber(frame_state);
@@ skipping 712 matching lines @@
 }
 
 
 MachineOperatorBuilder* JSTypedLowering::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8