TC39 General on 2022-11-08

08:59	<Jack Works>	Is it possible to freeze the [[Prototype]] of an ordinary object without wrapping it with Proxy?
10:13	<Ashley Claymore>	Nope. Can only make it non-extensible. Props and prototype all part of the same bag
10:40	<Ashley Claymore>	https://github.com/tc39/proposal-freeze-prototype
10:42	<Ashley Claymore>	https://matrixlogs.bakkot.com/TC39_Delegates/2021-09-20#L1
15:30	<nicolo-ribaudo>	Is there an es5 way of creating a function with length n (where n is known statically when I'm writing the code), and for which `IsConstructor` returns `false`?
15:51	<jmdyck>	As far as I can tell, in es5, the only functions that don't have a [[Construct]] internal method are all built-ins. So even without the length constraint, the answer looks like no.
16:11	<nicolo-ribaudo>	Ok thanks, that matches what I expected but I was hoping for secret hacks 😂 I know that I can create functions with length 0 and 1 using getters and setters in object literals, but it does not generalize to 2+ args.
18:19	<ljharb>	those functions are constructors tho, aren't they?
18:24	<nicolo-ribaudo>	Nope: `new (Object.getOwnPropertyDescriptor({ get x() {} }, "x").get) // TypeError: Object.getOwnPropertyDescriptor(...).get is not a constructor`
18:26	<littledan>	yeah, all concise methods, e.g., `new ({x() {}}.x)`
18:26	<littledan>	and arrow functions
18:44	<jmdyck>	Are you running that in an ES5 engine?
18:45	<littledan>	I am saying, those things are not constructors, and that code throws. I am using a new engine
18:46	<jmdyck>	and nicolo-ribaudo ?
18:46	<littledan>	oh sorry I missed the "es5" part of the question!
18:47	<jmdyck>	looks like semantics changed between es5 and es6
18:56	<Ashley Claymore>	Does that work in ES5? alt: Using a getter, but re defining length and accessing args via `arguments`
18:56	<Ashley Claymore>	or is it a valid constructor in es5?
19:02	<nicolo-ribaudo>	No, I only tested it in modern browsers. Thank you!
19:04	<nicolo-ribaudo>	For context, I was trying to figure out how to compile arrow functions to es5 in a 100% spec compliant way (mostly for fun, I'm not going to add this to Babel)
19:05	<nicolo-ribaudo>	sent an image. I thought that the length was non-configurable, this might work to at least keep the semantics of compiled code valid in modern engines 👀
19:07	<jmdyck>	In ES5, `get` PropertyName etc involves "the result of creating a new Function object as specified in 13.2", which always sets both [[Call]] and [[Construct]].
19:07	<jmdyck>	In ES6, it involves "FunctionCreate(~Method~, ...)", which leads to FunctionAllocate being called with `_functionKind_` = "non-constructor", which causes [[Construct]] to not be set.