Before, if we had a projection like `<T as Foo<'0>>::Bar: 'x` and a
where clause like `<T as Foo<'a>>::Bar: 'a`, we considered those to
have nothing to do with one another. Therefore, we would use the
"overconstrained" path of adding `T: 'x` and `'0: 'x` requirements. We
now do a "fuzzy" match where we erase regions first and hence we see
the env bound `'a`.
We used to apply it repeatedly as we went, relying on the current
value of the `region_bound_pairs_accum` vector. But now we save those
values into a map, so we can just process all the registered region
obligations at the end.
overlook overflows in rustdoc trait solving
Context:
The new rustdoc "auto trait" feature walks across impls and tries to run trait solving on them with a lot of unconstrained variables. This is prone to overflows. These overflows used to cause an ICE because of a caching bug (fixed in this PR). But even once that is fixed, it means that rustdoc causes an overflow rather than generating docs.
This PR therefore adds a new helper that propagates the overflow error out. This requires rustdoc to then decide what to do when it encounters such an overflow: technically, an overflow represents neither "yes" nor "no", but rather a failure to make a decision. I've decided to opt on the side of treating this as "yes, implemented", since rustdoc already takes an optimistic view. This may prove to include too many items, but I *suspect* not.
We could probably reduce the rate of overflows by unifying more of the parameters from the impl -- right now we only seem to consider the self type. Moreover, in the future, as we transition to Chalk, overflow errors are expected to just "go away" (in some cases, though, queries might return an ambiguous result).
Fixes#52873
cc @QuietMisdreavus -- this is the stuff we were talking about earlier
cc @GuillaumeGomez -- this supersedes #53687
Remove OneVector, increase related SmallVec capacities
Removes the `OneVector` type alias (equivalent to `SmallVec<[T; 1]>`); it is used in scenarios where the capacity of 1 is often exceeded, which might be nullifying the performance wins (due to spilling to the heap) expected when using `SmallVec` instead of `Vec`.
The numbers I used in this PR are very rough estimates - it would probably be a good idea to adjust some/all of them, which is what this proposal is all about.
It might be a good idea to additionally create some local type aliases for the `SmallVec`s in the `Folder` trait, as they are repeated in quite a few spots; I'd be happy to apply this sort of adjustments.
Stabilize pattern_parentheses feature
Addresses #51087 .
Stabilizes the previously unstable feature `pattern_parentheses` which enables the use of `()` in match patterns.
Rollup of 12 pull requests
Successful merges:
- #53518 (Add doc for impl From in char_convert)
- #54058 (Introduce the partition_dedup/by/by_key methods for slices)
- #54281 (Search box)
- #54368 (Reduce code block sides padding)
- #54498 (The project moved under the Mozilla umbrella)
- #54518 (resolve: Do not block derive helper resolutions on single import resolutions)
- #54522 (Fixed three small typos.)
- #54529 (aarch64-pc-windows-msvc: Don't link libpanic_unwind to libtest.)
- #54537 (Rename slice::exact_chunks() to slice::chunks_exact())
- #54539 (Fix js error)
- #54557 (incr.comp.: Don't automatically enable -Zshare-generics for incr. comp. builds.)
- #54558 (Improvements to finding LLVM's FileCheck)
Failed merges:
r? @ghost
