Proposal: strict built-in functions

Jack Works zjwpeter at
Sun Dec 8 19:49:58 UTC 2019

I thought the "caller" has been removed from the spec, so there isn't much
to do with the "caller" since it is not standard. It's implementation's own
But maybe we can also extend The forbidden extensions section.

On Mon, Dec 9, 2019, 1:12 AM Claude Pache <claude.pache at> wrote:

> Le 8 déc. 2019 à 14:43, Jack Works <zjwpeter at> a écrit :
> In the current spec, strictness of the built-in functions are
> implementation-dependent behaviors. This proposal is going to fix this
> problem.
> Hi,
> See for another
>  testcase.
> The real problem is that the semantics of `f.caller` is left to
> implementations. There are in fact some restrictions in the spec, see
>, but they are
> insufficient.
> Note that it doesn’t really make sense to mandate that builtin functions
> be “strict”: The notion of strictness is defined only for so-called
> ECMAScript functions, which are functions whose implementation is written
> in ECMAScript code. That excludes builtin functions (unless the
> implementation choose to  implement them in ECMAScript), but also bound
> functions, proxies, and probably some other cases.
> —Claude
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