Add bit removal methods to SparseBitMatrix and factor *BitSet relational methods into more extensible trait
I need the ability to clear the bits out of a row from `SparseBitMatrix`. Currently, all the mutating methods only allow insertion of bits, and there is no way to get access to the underlying data.
One approach is simply to make `ensure_row` public, since it grants `&mut` access to the underlying `HybridBitSet`. This PR adds the `pub` modifier. However, presumably this method was private for a reason, so I'm open to other designs. I would prefer general mutable access to the rows, because that way I can add many mutating operations (`clear`, `intersect`, etc.) without filing a PR each time :-)
r? `@ecstatic-morse`
Introduce `let...else`
Tracking issue: #87335
The trickiest part for me was enforcing the diverging else block with clear diagnostics. Perhaps the obvious solution is to expand to `let _: ! = ..`, but I decided against this because, when a "mismatched type" error is found in typeck, there is no way to trace where in the HIR the expected type originated, AFAICT. In order to pass down this information, I believe we should introduce `Expectation::LetElseNever(HirId)` or maybe add `HirId` to `Expectation::HasType`, but I left that as a future enhancement. For now, I simply assert that the block is `!` with a custom `ObligationCauseCode`, and I think this is clear enough, at least to start. The downside here is that the error points at the entire block rather than the specific expression with the wrong type. I left a todo to this effect.
Overall, I believe this PR is feature-complete with regard to the RFC.
Concrete regions can show up in mir borrowck if the originated from there
We used to not encounter them here, because we took regions from typeck's opaque type resolution by renumbering them. We don't do that anymore. Instead mir borrock does all the logic, and it can handle concrete regions just fine, as long as it created them itself.
fixes#83190 which was introduced by #87287
r? `@spastorino`
Clean up the lowering of AST items
This PR simplifies and improves `rustc_ast_lowering::item` in various minor ways. The reasons for the changes should mostly be self evident, though I'm happy to specifically explain anything if needed.
These changes used to be part of #88019, but I removed them after it was pointed out that some of my other changes to `rustc_ast_lowering` were unnecessary. It felt like a bad idea to clean up code which I didn't even need to touch anymore.
r? `@cjgillot`
Warn when [T; N].into_iter() is ambiguous in the new edition.
Fixes https://github.com/rust-lang/rust/issues/88475
In https://github.com/rust-lang/rust/issues/88475, a situation was found where `[T; N].into_iter()` becomes *ambiguous* in the new edition. This is different than the case where `(&[T; N]).into_iter()` resolves differently, which was the only case handled by the `array_into_iter` lint. This is almost identical to the new-traits-in-the-prelude problem. Effectively, due to the array-into-iter hack disappearing in Rust 2021, we effectively added `IntoIterator` to the 'prelude' in Rust 2021 specifically for arrays.
This modifies the prelude collisions lint to detect that case and emit a `array_into_iter` lint in that case.
Don't use `guess_head_span` in `predicates_of` for foreign span
Previously, the result of `predicates_of` for a foreign trait
would depend on the *current* state of the corresponding source
file in the foreign crate. This could lead to ICEs during incremental
compilation, since the on-disk contents of the upstream source file
could potentially change without the upstream crate being recompiled.
Additionally, this ensure that that the metadata we produce for a crate
only depends on its *compiled* upstream dependencies (e.g an rlib or
rmeta file), *not* the current on-disk state of the upstream crate
source files.
update const generics feature gates
**tl;dr: split const generics into three features: `adt_const_params`, `const_generics_defaults` and `generic_const_exprs`**
continuing the work of `@BoxyUwU` in #88324, this PR
- renames `feature(const_evaluatable_checked)` to `feature(generic_const_exprs)` which now doesn't need any other feature gate to work. Previously `feature(const_evaluatable_checked)` was only useful in combination with `feature(const_generics)`.
- completely removes `feature(lazy_normalization_consts)`. This feature only supplied the parents generics to anonymous constants, which is pretty useless as generic anon consts are only allowed with `feature(generic_const_exprs)` anyways.
- moves the ability to use additional const param types from `feature(const_generics)` into `feature(adt_const_params)`. As `feature(const_generics)` is now mostly useless without `feature(generic_const_exprs)` we also remove that feature flag.
- updates tests, removing duplicates and unnecessary revisions in some cases and also deletes all unused `*.stderr` files.
I not also remove the ordering restriction for const and type parameters if any of the three const generics features is active.
This ordering restriction feels like the only "real" use of the current `feature(const_generics)` right now so this change isn't a perfect solution, but as I intend to stabilize the ordering - and `feature(const_generics_defaults)` - in the very near future, I think this is acceptable for now.
---
cc `@rust-lang/project-const-generics` about the new feature names and this change in general.
I don't think we need any external approval for this change but I do intend to publish an update to the const generics tracking issue the day this PR lands, so I don't want this merged yet.
Apologies to whoever ends up reviewing this PR 😅❤️
r? rust-lang/project-const-generics
