TC39 General on 2021-08-24

05:35	<bakkot>	this is a very fun writeup of a CVE in chrome which happened as a consequence of a change to TypedArrays in the spec: https://tiszka.com/blog/CVE_2021_21225.html
05:36	<bakkot>	also serves as a good concrete example of Symbol.species causing bad things to happen
14:25	<shu>	yes, that was a "i'm in this picture and i don't like it" situation
15:12	<jschoi>	Looking at https://github.com/tc39/proposal-pattern-matching/issues/168#issuecomment-814216217, I’m wondering: Is it a goal to forever avoid the Bad Keywords (`eval`, `with`, `switch`) in new syntax? That is, is it a committee invariant that those three words not be used in any new syntax going forward?
15:42	<shu>	well, eval isn't a keyword
15:42	<shu>	and i've seen ideas float around that want to co-opt `with` for more useful purposes, it's a nice keyword
15:43	<shu>	so it's not an invariant from my perspective
16:04	<jschoi>	Yeah, I mean Bad Words in general, I guess, heh. An example for `eval`: https://github.com/tc39/proposal-do-expressions/issues/53#issuecomment-771789167
16:04	<jschoi>	I suppose I haven’t seen anything about this with `with` yet; I had assumed it was in a similar situation to `switch` etc. I don’t remember seeing any proposals actually using `with`.
16:23	<jschoi>	If `with` is going to be treated differently from `switch` (in that new syntax may use `with` but not `switch`), it might be good to make explicit how their situations are different. After all, they’re similarly discouraged (already discouraged for `with` and discouraged in the future for `switch` whenever `match` is standardized; see https://github.com/tc39/proposal-pattern-matching/issues/168#issuecomment-707404650). I suppose that `switch` and `match` have somewhat similar purposes, while no future syntax is going to have a purpose at all similar to `with`’s current purpose (dynamic binding)…so there might be less risk of confusion between `with`’s current purpose and any future syntax that reuses `with` for a completely different purpose, compared to `switch` and `match`. And so, if a future syntax somehow reused `switch` for a purpose completely different from pattern matching, then perhaps that too might be acceptable…though I cannot think of any such possible purpose for `switch`.
17:11	<ljharb>	jschoi: `with` has been discouraged for a long time, and can't be used in ESM or classes, so it's unlikely its use will cause confusion, especially since people will likely google `match with` and get to the right place. overlapping `match` and `switch`, however, will be quite confusing
17:11	<ljharb>	we could certainly use a different spelling than "with" if that's a concern tho
17:12	<ljharb>	iow, the goal is not "avoid bad keywords", it's "avoid switch, specifically, because it is the Bad Thing this exact proposal is trying to obviate"