[strong] Disallow implicit conversions for comparison

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'.
 
 
 /* -----------------------------------
    - - -   C o m p a r i s o n   - - -
    -----------------------------------
 */
 
 // The following declarations are shared with other native JS files.
 // They are all declared at this one spot to avoid redeclaration errors.
 var EQUALS;
 var STRICT_EQUALS;
 var COMPARE;
+var COMPARE_STRONG;
 var ADD;
 var ADD_STRONG;
 var STRING_ADD_LEFT;
 var STRING_ADD_LEFT_STRONG;
 var STRING_ADD_RIGHT;
 var STRING_ADD_RIGHT_STRONG;
 var SUB;
 var SUB_STRONG;
 var MUL;
 var MUL_STRONG;
@@ skipping 164 matching lines @@
   if (IS_STRING(left) && IS_STRING(right)) {
     return %_StringCompare(left, right);
   } else {
     var left_number = %$toNumber(left);
     var right_number = %$toNumber(right);
     if (NUMBER_IS_NAN(left_number) || NUMBER_IS_NAN(right_number)) return ncr;
     return %NumberCompare(left_number, right_number, ncr);
   }
 }
 
+// Strong mode COMPARE throws if an implicit conversion would be performed
+COMPARE_STRONG = function COMPARE_STRONG(x, ncr) {
+  if (IS_STRING(this) && IS_STRING(x)) return %_StringCompare(this, x);
+  if (IS_NUMBER(this) && IS_NUMBER(x)) return %NumberCompare(this, x, ncr);
+
+  throw %MakeTypeError('strong_implicit_cast');
+}
+
 
 
 /* -----------------------------------
    - - -   A r i t h m e t i c   - - -
    -----------------------------------
 */
 
 // ECMA-262, section 11.6.1, page 50.
 ADD = function ADD(x) {
   // Fast case: Check for number operands and do the addition.
@@ skipping 775 matching lines @@
 $toLength = ToLength;
 $toName = ToName;
 $toNumber = ToNumber;
 $toObject = ToObject;
 $toPositiveInteger = ToPositiveInteger;
 $toPrimitive = ToPrimitive;
 $toString = ToString;
 $toUint32 = ToUint32;
 
 })();