Unexpected semantics for util.is... #2197

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1. deian

   changed the title [-]Unexpected semantics for "is..."[/-] [+]Unexpected semantics for util.is...[/+] on Jul 16, 2015
2. brendanashworth

   added

   utilIssues and PRs related to the built-in util module.Issues and PRs related to the built-in util module.

   on Jul 17, 2015
3. Fishrock123 commented on Jul 17, 2015

   

   Fishrock123

   on Jul 17, 2015

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   The semantics almost certainly won't change. It is suggested you don't use these functions; I've been meaning to put deprecation notices into the docs.

   How do you suggest we clarify that that won't work?

   For posterity, the internals use Object.prototype.toString.call(input) === '[object RegExp]', since other methods can be bypassed, and this is the most reliable.
4. Fishrock123 commented on Jul 22, 2015

   

   Fishrock123

   on Jul 22, 2015

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   See also #2201
5. Ginden commented on Jul 26, 2015

   

   Ginden

   on Jul 26, 2015

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   For posterity, the internals use Object.prototype.toString.call(input) === '[object RegExp]', since other methods can be bypassed, and this is the most reliable.

   Symbol.toStringTag is implemented in Chrome and avalaible in io.js behind --es_staging flag.

   Anyway - Object.create(RegExp.prototype) is not a RegExp.

   > p = Object.create(RegExp.prototype);
    {}
   > p.compile()
   illegal access
   > p.source
   '(?:)'
   > p.test('aaa')
   TypeError: Method RegExp.prototype.test called on incompatible receiver [object Object]
   

   ES6 allows to create classes extending RegExps, but it isn't implemented in any engine yet.
6. deian commented on Jul 27, 2015

   

   deian

   on Jul 27, 2015

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   @Fishrock123 thanks. I think the deprecation notice is a fine solution.

   I'm not sure if it helps, but saying that the function returns true for objects created with the RegExp constructor would also be clear. (@Ginden a description what is not a RegExp is not necessarily useful.)
7. Fishrock123 commented on Aug 25, 2015

   

   Fishrock123

   on Aug 25, 2015

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   Deprecated in the docs as of 93e2830, see #2447
8. Fishrock123

   closed this as completedon Aug 25, 2015