| 02:19 | <jmdyck> | Does anyone know why ScriptEvaluation asserts that the execution context stack (on exit and presumably entry) isn't empty? |
| 02:20 | <jmdyck> | I can understand why HTML might want it to be the case, but that's HTML's problem. |
| 02:21 | <jmdyck> | Why does EcmaScript care whether it's empty or not? |
| 02:35 | <bakkot> | I would guess it is just there as a consistency check: every time a context is added, it is later removed |
| 02:37 | <snek> | i think the spec assumes you have an outer execution context that is kept with the realm |
| 02:37 | <snek> | but |
| 02:37 | <snek> | i don't think its really necessary |
| 02:38 | <jmdyck> | @bakkot: Hm, asserting non-empty on exit isn't a very good way to achieve that consistency check. |
| 02:39 | <snek> | we already have that consistency check built into the stack operation itself |
| 02:40 | <snek> |
presumably if this is a stack, there's only one thing you can remove |
| 02:41 | <jmdyck> | I don't think there was a suggestion of ambiguity as to what to remove |
| 02:42 | <jmdyck> | It would be useful to assert, e.g. that ScriptEvaluation leaves the EC stack the way it found it. |
| 02:43 | <snek> | idk if it would be more useful than any other op that modifies the stack |
| 02:43 | <snek> | (which is not to say it wouldn't be useful) |
| 02:44 | <jmdyck> | Some stack-manipulating AOs do this by grabbing the running execution context before pushing, then after popping, saying that the pop restores the former running EC. |
| 02:44 | <jmdyck> | But that's not what ScriptEvaluation does. |
| 02:45 | <jmdyck> | Merely asserting a non-empty stack on exit doesn't achieve that at all. |
| 02:46 | <snek> | can i just say how much i love that SS and RS are grouped together now |
| 02:47 | <snek> | i think "Resume the context that is now on the top of the execution context stack as the running execution context." is pretty standard |
| 02:47 | <snek> | the assertion is not though |
| 02:50 | <jmdyck> | There are 7 occurrences of "Remove X from the EC stack and restore Y as the running EC." |
| 02:51 | <snek> | "restore" 🤔 |
| 02:53 | <jmdyck> | (Actually, they're all literally Remove _calleeContext_ from the execution context stack and restore _callerContext_ as the running execution context.) |
| 02:57 | <jmdyck> | There's 3 occurrences of Resume the context that is now on the top of the execution context stack as the running execution context. |
| 02:59 | <snek> | yeah |
| 03:00 | <snek> | do we ever define what it means to suspend and resume contexts |
| 03:00 | <snek> | "restore" aside |
| 03:01 | <jmdyck> | We don't. |
| 03:03 | <jmdyck> | But see https://github.com/tc39/ecma262/pull/2962, which gets rid of "suspend" and "resume" as applied to ECs. |
| 03:04 | <jmdyck> | (Also, its first commit gets rid of "restore".) |