[strong] no sloppy equality

src/messages.js

 // Copyright 2012 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.
 
 // -------------------------------------------------------------------
 
 var kMessages = {
   // Error
   cyclic_proto:                  ["Cyclic __proto__ value"],
   code_gen_from_strings:         ["%0"],
@@ skipping 143 matching lines @@
   strict_octal_literal:          ["Octal literals are not allowed in strict mode."],
   template_octal_literal:        ["Octal literals are not allowed in template strings."],
   strict_delete:                 ["Delete of an unqualified identifier in strict mode."],
   strict_delete_property:        ["Cannot delete property '", "%0", "' of ", "%1"],
   strict_const:                  ["Use of const in strict mode."],
   strict_function:               ["In strict mode code, functions can only be declared at top level or immediately within another function." ],
   strict_read_only_property:     ["Cannot assign to read only property '", "%0", "' of ", "%1"],
   strict_cannot_assign:          ["Cannot assign to read only '", "%0", "' in strict mode"],
   strict_poison_pill:            ["'caller', 'callee', and 'arguments' properties may not be accessed on strict mode functions or the arguments objects for calls to them"],
   strict_caller:                 ["Illegal access to a strict mode caller function."],
+  strong_equal:                  ["Please don't use '==' or '!=' in strong mode, use '===' or '!==' instead"],

[marja, 2015/02/12 09:59:37]

I find this error message strangely polite :) How about:

'==' and '!=' not allowed in strong mode

[rossberg, 2015/02/12 14:47:16]

Totally intentional, I thought people should think good of strong mode instead
of feeling harassed. :)

The "please" might be over the top, but at least I'd like strong mode errors to
point out the recommended alternative to using the forbidden feature.

   malformed_arrow_function_parameter_list: ["Malformed arrow function parameter list"],
   generator_poison_pill:         ["'caller' and 'arguments' properties may not be accessed on generator functions."],
   cant_prevent_ext_external_array_elements: ["Cannot prevent extension of an object with external array elements"],
   redef_external_array_element:  ["Cannot redefine a property of an object with external array elements"],
   harmony_const_assign:          ["Assignment to constant variable."],
   symbol_to_string:              ["Cannot convert a Symbol value to a string"],
   symbol_to_primitive:           ["Cannot convert a Symbol wrapper object to a primitive value"],
   symbol_to_number:              ["Cannot convert a Symbol value to a number"],
   invalid_module_path:           ["Module does not export '", "%0", "', or export is not itself a module"],
   module_type_error:             ["Module '", "%0", "' used improperly"],
@@ skipping 1140 matching lines @@
 function SetUpStackOverflowBoilerplate() {
   var boilerplate = MakeRangeError('stack_overflow', []);
 
   %DefineAccessorPropertyUnchecked(
       boilerplate, 'stack', StackTraceGetter, StackTraceSetter, DONT_ENUM);
 
   return boilerplate;
 }
 
 var kStackOverflowBoilerplate = SetUpStackOverflowBoilerplate();