---------- Forwarded message --------- From: guest271314 <[email protected]> Date: Thu, Mar 28, 2019 at 12:19 AM Subject: Re: Proposal: Static Typing To: Claude Pache <[email protected]>
> `a = object[Math.random() < 0.5 ? "method_returning_number" : "method_returning_string"]()` Interesting case. See also How do I check if a JavaScript function returns a Promise? > <https://stackoverflow.com/q/43416214> Say I have two functions: > ```function f1() { > return new Promise<any>((resolve, reject) => { > resolve(true); > }); > } > function f2() { > }``` > How do I know if f1 will return Promise and f2 will not? Can a regular expression be crafted which determines the return type of a function? <https://stackoverflow.com/q/43417236> Has it been mathematically proven that antivirus can't detect all viruses? <https://security.stackexchange.com/q/201992> On Wed, Mar 27, 2019 at 6:10 PM Claude Pache <[email protected]> wrote: > > > Le 27 mars 2019 à 18:26, Michael Theriot <[email protected]> > a écrit : > > Would an error at runtime or compiletime occur here? > > > The check cannot be reliably done at compile time in general; it must be a > runtime check. (Tools may provide partial static analysis, but that’s an > extra.) > > The simplest reason is that statically typed code must run together with > non-statically typed code. > > And even ignoring legacy code, it is not desirable to have static types > everywhere; for instance, `Array.prototype.sort()` must continue to work > with both arrays of strings and arrays of numbers, and even with arrays of > mixed types. > > And even if everything everywhere was statically typed, you still cannot > statically analyse situations like: `a = object[Math.random() < 0.5 ? > "method_returning_number" : "method_returning_string"]()`. > > If it is a runtime error, is it optimal for the engine to keep track of > typed variables vs regular for the same value? > > > Today’s JS engines typically do already clever speculative optimisations > based on expected types. For example: https://stackoverflow.com/a/46144917. > So, I guess, it depends... > > —Claude > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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