erichkeane added a comment.
In D124351#3950805 <https://reviews.llvm.org/D124351#3950805>, @cor3ntin wrote:
> Rebase. This is still a bit rough, I have a few tests to fix
> and some dead code to remove.
>
> ---
>
> @erichkeane I wouldn't mind picking your brain on this.
> Consider:
>
> template <typename T>
> void dependent_init_capture(T x = 0) {
> [y = x] () requires (decltype(y){1}) {
> return y;
> }();
> }
>
> void test_dependent() {
> dependent_init_capture(0);
> }
>
> This used to ""work"" in the previous iteration of the patch,
> but with the late concept checking it seems more involved.
>
> My understanding so far is that in `CheckFunctionConstraints`
> we can't find an instanciated declaration of `y` (so it asserts in
> `LocalInstantiationScope::findInstantiationOf`).
>
> I'm not 100% sure of what's the correct approach here would be.
> My guess is that we might need to retransform the captures in the
> instanciation scope used
> for constraint checking?
> I'm not actually sure whether an instanciation of the lambda does exist at
> that point in some other scope,
> though. Ideally we would not instannciate lambdas more times than needed.
>
> Another issue is that there is no way to walk back from a call expression to
> a lambda expression,
> so we might need to add that.
We shouldnn't -re-transform' the capture, but we need to make sure we get it
into the current scope. I haven't looked at lambda instantiation much, so I
don't know where that 'y' usually ends up? Can you do a run of it when it
WORKS and see where it finds that when calling `FindInstantiatedDecl`. I'm
guessing we are currently counting on that coming from a PARENT of the
`CurrentInstantiationScope` (one of the `Outer`s), which we can no longer count
on.
`FindInstantiatedDecl` needs some unfortunate amount of work around lambdas, I
found similar issues when working on https://reviews.llvm.org/D138148 which I
need to get back to when I re-start work next year.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D124351/new/
https://reviews.llvm.org/D124351
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