match lowering: expand or-candidates mixed with candidates above
This PR tweaks match lowering of or-patterns. Consider this:
```rust
match (x, y) {
(1, true) => 1,
(2, false) => 2,
(1 | 2, true | false) => 3,
(3 | 4, true | false) => 4,
_ => 5,
}
```
One might hope that this can be compiled to a single `SwitchInt` on `x` followed by some boolean checks. Before this PR, we compile this to 3 `SwitchInt`s on `x`, because an arm that contains more than one or-pattern was compiled on its own. This PR groups branch `3` with the two branches above, getting us down to 2 `SwitchInt`s on `x`.
We can't in general expand or-patterns freely, because this interacts poorly with another optimization we do: or-pattern simplification. When an or-pattern doesn't involve bindings, we branch the success paths of all its alternatives to the same block. The drawback is that in a case like:
```rust
match (1, true) {
(1 | 2, false) => unreachable!(),
(2, _) => unreachable!(),
_ => {}
}
```
if we used a single `SwitchInt`, by the time we test `false` we don't know whether we came from the `1` case or the `2` case, so we don't know where to go if `false` doesn't match.
Hence the limitation: we can process or-pattern alternatives alongside candidates that precede it, but not candidates that follow it. (Unless the or-pattern is the only remaining match pair of its candidate, in which case we can process it alongside whatever).
This PR allows the processing of or-pattern alternatives alongside candidates that precede it. One benefit is that we now process or-patterns in a single place in `mod.rs`.
r? ``@matthewjasper``
Suggest removing unused tuple fields if they are the last fields
Fixes#124556
We now check if dead/unused fields are the last fields of the tuple and suggest their removal instead of suggesting them to be changed to `()`.
Replace `move||` with `move ||`
Edit from #126631 to revert changes in `tests/ui`.
There are 18 instances of `move||` across 6 files in the repo:
- `compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs`
- `library/core/src/sync/atomic.rs`
- `library/std/src/sync/condvar.rs`
- `library/std/src/sync/mpsc/mod.rs`
- `library/std/src/sync/barrier.rs`
- `library/std/src/thread/local.rs`
I have replaced all such instances with `move ||` instead as it better adheres to modern formatting standards.
Ideally, we would have this automated by rustfmt or some other tool, but I do not have the time to implement such a feature or tool.
Nonetheless, I would encourage any effort invested into such a tool or feature.
hir_typeck: be more conservative in making "note caller chooses ty param" note
In https://github.com/rust-lang/rust/pull/122195 I added a "caller chooses ty for type param" note for when the return expression type a.k.a. found type does not match the expected return type.
#126547 found that this note was confusing when the found return type *contains* the expected type, e.g.
```rs
fn f<T>(t: &T) -> T {
t
}
```
because the found return type `&T` will *always* be different from the expected return type `T`, so the note was needlessly redundant and confusing.
This PR addresses that by not making the note if the found return type contains the expected return type.
r? ``@fmease`` (since you reviewed the original PR)
Fixes https://github.com/rust-lang/rust/issues/126547
safe transmute: support non-ZST, variantful, uninhabited enums
Previously, `Tree::from_enum`'s implementation branched into three disjoint cases:
1. enums that uninhabited
2. enums for which all but one variant is uninhabited
3. enums with multiple variants
This branching (incorrectly) did not differentiate between variantful and variantless uninhabited enums. In both cases, we assumed (and asserted) that uninhabited enums are zero-sized types. This assumption is false for enums like:
enum Uninhabited { A(!, u128) }
...which, currently, has the same size as `u128`. This faulty assumption manifested as the ICE reported in #126460.
In this PR, we revise the first case of `Tree::from_enum` to consider only the narrow category of "enums that are uninhabited ZSTs". These enums, whose layouts are described with `Variants::Single { index }`, are special in their layouts otherwise resemble the `!` type and cannot be descended into like typical enums. This first case captures uninhabited enums like:
enum Uninhabited { A(!, !), B(!) }
The second case is revised to consider the broader category of "enums that defer their layout to one of their variants"; i.e., enums whose layouts are described with `Variants::Single { index }` and that do have a variant at `index`. This second case captures uninhabited enums that are not ZSTs, like:
enum Uninhabited { A(!, u128) }
...which represent their variants with `Variants::Single`.
Finally, the third case is revised to cover the broader category of "enums with multiple variants", which captures uninhabited enums like:
enum Uninhabited { A(u8, !), B(!, u32) }
...which represent their variants with `Variants::Multiple`.
This PR also adds a comment requested by ````@RalfJung```` in his review of #126358 to `compiler/rustc_const_eval/src/interpret/discriminant.rs`.
Fixes#126460
r? ````@compiler-errors````
Suggest using a standalone doctest for non-local impl defs
This PR tweaks the lint output of the `non_local_definitions` lint to suggest using a standalone doctest instead of a moving the `impl` def to an impossible place as was already done with `macro_rules!` case in https://github.com/rust-lang/rust/pull/124568.
Fixes#126339
r? ```@fmease```
Place tail expression behind terminating scope
This PR implements #123739 so that we can do further experiments in nightly.
A little rewrite has been applied to `for await` lowering. It was previously `unsafe { Pin::unchecked_new(into_async_iter(..)) }`. Under the edition 2024 rule, however, `into_async_iter` gets dropped at the end of the `unsafe` block. This presumably the first Edition 2024 migration rule goes by hoisting `into_async_iter(..)` into `match` one level above, so it now looks like the following.
```rust
match into_async_iter($iter_expr) {
ref mut iter => match unsafe { Pin::unchecked_new(iter) } {
...
}
}
```
delegation: Implement glob delegation
Support delegating to all trait methods in one go.
Overriding globs with explicit definitions is also supported.
The implementation is generally based on the design from https://github.com/rust-lang/rfcs/pull/3530#issuecomment-2020869823, but unlike with list delegation in https://github.com/rust-lang/rust/pull/123413 we cannot expand glob delegation eagerly.
We have to enqueue it into the queue of unexpanded macros (most other macros are processed this way too), and then a glob delegation waits in that queue until its trait path is resolved, and enough code expands to generate the identifier list produced from the glob.
Glob delegation is only allowed in impls, and can only point to traits.
Supporting it in other places gives very little practical benefit, but significantly raises the implementation complexity.
Part of https://github.com/rust-lang/rust/issues/118212.
- Avoid "caller chooses ty for type param" note if the found type a.k.a.
the return expression type *contains* the type parameter, because e.g.
`&T` will always be different from `T` (i.e. "well duh").
- Rename `note_caller_chooses_ty_for_ty_param` to
`try_note_caller_chooses_ty_for_ty_param` because the note is not
always made.
Issue: https://github.com/rust-lang/rust/issues/126547
Uplift next trait solver to `rustc_next_trait_solver`
🎉
There's so many FIXMEs! Sorry! Ideally this merges with the FIXMEs and we track and squash them over the near future.
Also, this still doesn't build on anything other than rustc. I still need to fix `feature = "nightly"` in `rustc_type_ir`, and remove and fix all the nightly feature usage in the new trait solver (notably: let-chains).
Also, sorry `@lcnr` I know you asked for me to separate the commit where we `mv rustc_trait_selection/solve/... rustc_next_trait_solver/solve/...`, but I had already done all the work by that point. Luckily, `git` understands the file moves so it should still be relatively reviewable.
If this is still very difficult to review, then I can do some rebasing magic to try to separate this out. Please let me know!
r? lcnr
Replace all `&DiagCtxt` with a `DiagCtxtHandle<'_>` wrapper type
r? `@davidtwco`
This paves the way for tracking more state (e.g. error tainting) in the diagnostic context handle
Basically I will add a field to the `DiagCtxtHandle` that refers back to the `InferCtxt`'s (and others) `Option<ErrorHandled>`, allowing us to immediately taint these contexts when emitting an error and not needing manual tainting anymore (which is easy to forget and we don't do in general anyway)
coverage: Add debugging flag `-Zcoverage-options=no-mir-spans`
When set, this flag skips the code that normally extracts coverage spans from MIR statements and terminators. That sometimes makes it easier to debug branch coverage and MC/DC coverage instrumentation, because the coverage output is less noisy.
For internal debugging only. If future code changes would make it hard to keep supporting this flag, it should be removed at that time.
`@rustbot` label +A-code-coverage
Rework `feature(precise_capturing)` to represent `use<...>` as a syntactical bound
Reworks `precise_capturing` for a recent lang-team consensus.
Specifically:
> The conclusion of the team is that we'll make use<..> a bound. That is, we'll support impl use<..> + Trait, impl Trait + use<..>, etc.
> For now, we will support at most one such bound in a list of bounds, and semantically we'll only support these bounds in the item bounds of RPIT-like impl Trait opaque types (i.e., in the places discussed in the RFC).
Lang decision in favor of this approach:
- https://github.com/rust-lang/rust/issues/125836#issuecomment-2151351849
Tracking:
- https://github.com/rust-lang/rust/issues/123432
Rename `InstanceDef` -> `InstanceKind`
Renames `InstanceDef` to `InstanceKind`. The `Def` here is confusing, and makes it hard to distinguish `Instance` and `InstanceDef`. `InstanceKind` makes this more obvious, since it's really just describing what *kind* of instance we have.
Not sure if this is large enough to warrant a types team MCP -- it's only 53 files. I don't personally think it does, but happy to write one if anyone disagrees. cc ``@rust-lang/types``
r? types
Rollup of 3 pull requests
Successful merges:
- #126568 (mark undetermined if target binding in current ns is not got)
- #126577 (const_refs_to_static test and cleanup)
- #126584 (Do not ICE in privacy when type inference fails.)
r? `@ghost`
`@rustbot` modify labels: rollup
const_refs_to_static test and cleanup
r? ``@RalfJung``
test the existing behaviour of adt_const_params combined with const_refs_to_static.
also remove a dead error variant about consts referring to statics
Consistently use subtyping in method resolution
fixes#126062
An earlier version of this PR modified how we compute variance, but the root cause was an inconsistency between the usage of `eq` and `sub`, where we assumed that the latter passing implies the former will pass.
r? `@compiler-errors`
When set, this flag skips the code that normally extracts coverage spans from
MIR statements and terminators. That sometimes makes it easier to debug branch
coverage and MC/DC coverage, because the coverage output is less noisy.
For internal debugging only. If other code changes would make it hard to keep
supporting this flag, remove it.
Rollup of 3 pull requests
Successful merges:
- #126226 (Make suggestion to change `Fn` to `FnMut` work with methods as well)
- #126570 (Convert a `span_bug` to a `span_delayed_bug`.)
- #126580 (Add `run-make/const_fn_mir` missing test annotation)
r? `@ghost`
`@rustbot` modify labels: rollup
Convert a `span_bug` to a `span_delayed_bug`.
PR #121208 converted this from a `span_delayed_bug` to a `span_bug` because nothing in the test suite caused execution to hit this path. But now fuzzing has found a test case that does hit it. So this commit converts it back to `span_delayed_bug` and adds the relevant test.
Fixes#126385.
r? `@lcnr`
Make suggestion to change `Fn` to `FnMut` work with methods as well
Fixes#125325
The issue occurred because the code that emitted the suggestion to change `Fn` to `FnMut` worked only for function calls and not method calls. This PR makes it work with methods as well.
