[strong] Disallow implicit conversions for add

src/runtime.js

 // Copyright 2006-2008 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.
 
 // This files contains runtime support implemented in JavaScript.
 
 // CAUTION: Some of the functions specified in this file are called
 // directly from compiled code. These are the functions with names in
 // ALL CAPS. The compiled code passes the first argument in 'this'.
 
@@ skipping 142 matching lines @@
   if (IS_STRING(a)) {
     return %_StringAdd(a, %ToString(b));
   } else if (IS_STRING(b)) {
     return %_StringAdd(%NonStringToString(a), b);
   } else {
     return %NumberAdd(%ToNumber(a), %ToNumber(b));
   }
 }
 
 
+//ECMA-262, section 11.6.1, page 50.

[Dmitry Lomov (no reviews), 2015/04/30 08:43:59]

This comment does not apply anymore I guess.

[conradw, 2015/04/30 09:19:33]

Changed this and similar examples in other places.

+function ADD_STRONG(x) {
+  if (IS_NUMBER(this) && IS_NUMBER(x)) return %NumberAdd(this, x);
+  if (IS_STRING(this) && IS_STRING(x)) return %_StringAdd(this, x);
+
+  throw %MakeTypeError('strong_implicit_cast');
+}
+
+
 // Left operand (this) is already a string.
 function STRING_ADD_LEFT(y) {
   if (!IS_STRING(y)) {
     if (IS_STRING_WRAPPER(y) && %_IsStringWrapperSafeForDefaultValueOf(y)) {
       y = %_ValueOf(y);
     } else {
       y = IS_NUMBER(y)
           ? %_NumberToString(y)
           : %ToString(%ToPrimitive(y, NO_HINT));
     }
   }
   return %_StringAdd(this, y);
 }
 
 
+//Left operand (this) is already a string.
+function STRING_ADD_LEFT_STRONG(y) {
+  if (IS_STRING(y)) {
+    return %_StringAdd(this, y);
+  }
+  throw %MakeTypeError('strong_implicit_cast');
+}
+
+
 // Right operand (y) is already a string.
 function STRING_ADD_RIGHT(y) {
   var x = this;
   if (!IS_STRING(x)) {
     if (IS_STRING_WRAPPER(x) && %_IsStringWrapperSafeForDefaultValueOf(x)) {
       x = %_ValueOf(x);
     } else {
       x = IS_NUMBER(x)
           ? %_NumberToString(x)
           : %ToString(%ToPrimitive(x, NO_HINT));
     }
   }
   return %_StringAdd(x, y);
 }
 
 
+//Right operand (y) is already a string.
+function STRING_ADD_RIGHT_STRONG(y) {
+  if (IS_STRING(this)) {
+    return %_StringAdd(this, y);
+  }
+  throw %MakeTypeError('strong_implicit_cast');
+}
+
+
 // ECMA-262, section 11.6.2, page 50.
 function SUB(y) {
   var x = IS_NUMBER(this) ? this : %NonNumberToNumber(this);
   if (!IS_NUMBER(y)) y = %NonNumberToNumber(y);
   return %NumberSub(x, y);
 }
 
 
 // ECMA-262, section 11.6.2, page 50.
 function SUB_STRONG(y) {
@@ skipping 662 matching lines @@
 
 /* -----------------------------------------------
    - - -   J a v a S c r i p t   S t u b s   - - -
    -----------------------------------------------
 */
 
 function STRING_LENGTH_STUB(name) {
   var receiver = this;  // implicit first parameter
   return %_StringGetLength(%_JSValueGetValue(receiver));
 }