| Age | Commit message (Collapse) | Author | Lines |
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These were low value even before #137978 resulted in empty names being
used much less. (Why check for non-emptiness in these three places?
There are thousands of places in the compiler you could check.)
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nnethercote:rm-Nonterminal-and-TokenKind-Interpolated, r=petrochenkov
Remove `Nonterminal` and `TokenKind::Interpolated`
A third attempt at this; the first attempt was #96724 and the second was #114647.
r? `@ghost`
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r=compiler-errors
Allow parenthesis around inferred array lengths
In #135272 it was noticed that we weren't handling `Vec<(((((_)))))>` correctly under the new desugaring for `generic_arg_infer`, this had to be fixed in order to not regress stable code for types that should continue working. This has the side effect of *also* allowing the following to work:
```rust
#![feature(generic_arg_infer)]
struct Bar<const N: usize>;
fn main() {
let a: Bar<((_))> = Bar::<10>;
}
```
However I did not make the same change for array lengths resulting in the following not compiling:
```rust
#![feature(generic_arg_infer)]
fn main() {
let a: [u8; (((_)))] = [2; 2];
let a: [u8; 2] = [2; (((((_)))))];
}
```
This is rather inconsistent as parenthesis around `_` *are* supported for const args to non-arrays, and type args. This PR fixes this allowing the above example to compile. No stable impact.
r? compiler-errors
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It bugs me when variables of type `Ident` are called `name`. It leads to
silly things like `name.name`. `Ident` variables should be called
`ident`, and `name` should be used for variables of type `Symbol`.
This commit improves things by by doing `s/name/ident/` on a bunch of
`Ident` variables. Not all of them, but a decent chunk.
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Implement `super let`
Tracking issue: https://github.com/rust-lang/rust/issues/139076
This implements `super let` as proposed in #139080, based on the following two equivalence rules.
1. For all expressions `$expr` in any context, these are equivalent:
- `& $expr`
- `{ super let a = & $expr; a }`
2. And, additionally, these are equivalent in any context when `$expr` is a temporary (aka rvalue):
- `& $expr`
- `{ super let a = $expr; & a }`
So far, this experiment has a few interesting results:
## Interesting result 1
In this snippet:
```rust
super let a = f(&temp());
```
I originally expected temporary `temp()` would be dropped at the end of the statement (`;`), just like in a regular `let`, because `temp()` is not subject to temporary lifetime extension.
However, it turns out that that would break the fundamental equivalence rules.
For example, in
```rust
g(&f(&temp()));
```
the temporary `temp()` will be dropped at the `;`.
The first equivalence rule tells us this must be equivalent:
```rust
g({ super let a = &f(&temp()); a });
```
But that means that `temp()` must live until the last `;` (after `g()`), not just the first `;` (after `f()`).
While this was somewhat surprising to me at first, it does match the exact behavior we need for `pin!()`: The following _should work_. (See also https://github.com/rust-lang/rust/issues/138718)
```rust
g(pin!(f(&mut temp())));
```
Here, `temp()` lives until the end of the statement. This makes sense from the perspective of the user, as no other `;` or `{}` are visible. Whether `pin!()` uses a `{}` block internally or not should be irrelevant.
This means that _nothing_ in a `super let` statement will be dropped at the end of that super let statement. It does not even need its own scope.
This raises questions that are useful for later on:
- Will this make temporaries live _too long_ in cases where `super let` is used not in a hidden block in a macro, but as a visible statement in code like the following?
```rust
let writer = {
super let file = File::create(&format!("/home/{user}/test"));
Writer::new(&file)
};
```
- Is a `let` statement in a block still the right syntax for this? Considering it has _no_ scope of its own, maybe neither a block nor a statement should be involved
This leads me to think that instead of `{ super let $pat = $init; $expr }`, we might want to consider something like `let $pat = $init in $expr` or `$expr where $pat = $init`. Although there are also issues with these, as it isn't obvious anymore if `$init` should be subject to temporary lifetime extension. (Do we want both `let _ = _ in ..` and `super let _ = _ in ..`?)
## Interesting result 2
What about `super let x;` without initializer?
```rust
let a = {
super let x;
x = temp();
&x
};
```
This works fine with the implementation in this PR: `x` is extended to live as long as `a`.
While it matches my expectations, a somewhat interesting thing to realize is that these are _not_ equivalent:
- `super let x = $expr;`
- `super let x; x = $expr;`
In the first case, all temporaries in $expr will live at least as long as (the result of) the surrounding block.
In the second case, temporaries will be dropped at the end of the assignment statement. (Because the assignment statement itself "is not `super`".)
This difference in behavior might be confusing, but it _might_ be useful.
One might want to extend the lifetime of a variable without extending all the temporaries in the initializer expression.
On the other hand, that can also be expressed as:
- `let x = $expr; super let x = x;` (w/o temporary lifetime extension), or
- `super let x = { $expr };` (w/ temporary lifetime extension)
So, this raises these questions:
- Do we want to accept `super let x;` without initializer at all?
- Does it make sense for statements other than let statements to be "super"? An expression statement also drops temporaries at its `;`, so now that we discovered that `super let` basically disables that `;` (see interesting result 1), is there a use to having other statements without their own scope? (I don't think that's ever useful?)
## Interesting result 3
This works now:
```rust
super let Some(x) = a.get(i) else { return };
```
I didn't put in any special cases for `super let else`. This is just the behavior that 'naturally' falls out when implementing `super let` without thinking of the `let else` case.
- Should `super let else` work?
## Interesting result 4
This 'works':
```rust
fn main() {
super let a = 123;
}
```
I didn't put in any special cases for `super let` at function scope. I had expected the code to cause an ICE or other weird failure when used at function body scope, because there's no way to let the variable live as long as the result of the function.
This raises the question:
- Does this mean that this behavior is the natural/expected behavior when `super let` is used at function scope? Or is this just a quirk and should we explicitly disallow `super let` in a function body? (Probably the latter.)
---
The questions above do not need an answer to land this PR. These questions should be considered when redesigning/rfc'ing/stabilizing the feature.
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Add new `PatKind::Missing` variants
To avoid some ugly uses of `kw::Empty` when handling "missing" patterns, e.g. in bare fn tys. Helps with #137978. Details in the individual commits.
r? ``@oli-obk``
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These are no longer needed now that `Nonterminal` is gone.
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They are no longer needed.
This does slightly worsen the error message for a single test, but that
test contains code that is so badly broken that I'm not worried about
it.
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`hir::Lifetime::ident` currently sometimes uses `kw::Empty` for elided
lifetimes and sometimes uses `kw::UnderscoreLifetime`, and the
distinction is used when creating some error suggestions, e.g. in
`Lifetime::suggestion` and `ImplicitLifetimeFinder::visit_ty`. I found
this *really* confusing, and it took me a while to understand what was
going on.
This commit replaces all uses of `kw::Empty` in `hir::Lifetime::ident`
with `kw::UnderscoreLifetime`. It adds a new field
`hir::Lifetime::is_path_anon` that mostly replaces the old
empty/underscore distinction and makes things much clearer.
Some other notable changes:
- Adds a big comment to `Lifetime` talking about permissable field
values.
- Adds some assertions in `new_named_lifetime` about what ident values
are permissible for the different `LifetimeRes` values.
- Adds a `Lifetime::new` constructor that does some checking to make
sure the `is_elided` and `is_anonymous` states are valid.
- `add_static_impl_trait_suggestion` now looks at `Lifetime::res`
instead of the ident when creating the suggestion. This is the one
case where `is_path_anon` doesn't replace the old empty/underscore
distinction.
- A couple of minor pretty-printing improvements.
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Thanks to the introduction of `PatKind::Missing`.
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"Missing" patterns are possible in bare fn types (`fn f(u32)`) and
similar places. Currently these are represented in the AST with
`ast::PatKind::Ident` with no `by_ref`, no `mut`, an empty ident, and no
sub-pattern. This flows through to `{hir,thir}::PatKind::Binding` for
HIR and THIR.
This is a bit nasty. It's very non-obvious, and easy to forget to check
for the exceptional empty identifier case.
This commit adds a new variant, `PatKind::Missing`, to do it properly.
The process I followed:
- Add a `Missing` variant to `{ast,hir,thir}::PatKind`.
- Chang `parse_param_general` to produce `ast::PatKind::Missing`
instead of `ast::PatKind::Missing`.
- Look through `kw::Empty` occurrences to find functions where an
existing empty ident check needs replacing with a `PatKind::Missing`
check: `print_param`, `check_trait_item`, `is_named_param`.
- Add a `PatKind::Missing => unreachable!(),` arm to every exhaustive
match identified by the compiler.
- Find which arms are actually reachable by running the test suite,
changing them to something appropriate, usually by looking at what
would happen to a `PatKind::Ident`/`PatKind::Binding` with no ref, no
`mut`, an empty ident, and no subpattern.
Quite a few of the `unreachable!()` arms were never reached. This makes
sense because `PatKind::Missing` can't happen in every pattern, only
in places like bare fn tys and trait fn decls.
I also tried an alternative approach: modifying `ast::Param::pat` to
hold an `Option<P<Pat>>` instead of a `P<Pat>`, but that quickly turned
into a very large and painful change. Adding `PatKind::Missing` is much
easier.
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Ensure `define_opaque` attrs are accounted for in HIR hash
Fixes #138948
r? oli-obk
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r=oli-obk,traviscross
Stabilize `#![feature(precise_capturing_in_traits)]`
# Precise capturing (`+ use<>` bounds) in traits - Stabilization Report
Fixes https://github.com/rust-lang/rust/issues/130044.
## Stabilization summary
This report proposes the stabilization of `use<>` precise capturing bounds in return-position impl traits in traits (RPITITs). This completes a missing part of [RFC 3617 "Precise capturing"].
Precise capturing in traits was not ready for stabilization when the first subset was proposed for stabilization (namely, RPITs on free and inherent functions - https://github.com/rust-lang/rust/pull/127672) since this feature has a slightly different implementation, and it hadn't yet been implemented or tested at the time. It is now complete, and the type system implications of this stabilization are detailed below.
## Motivation
Currently, RPITITs capture all in-scope lifetimes, according to the decision made in the ["lifetime capture rules 2024" RFC](https://rust-lang.github.io/rfcs/3498-lifetime-capture-rules-2024.html#return-position-impl-trait-in-trait-rpitit). However, traits can be designed such that some lifetimes in arguments may not want to be captured. There is currently no way to express this.
## Major design decisions since the RFC
No major decisions were made. This is simply an extension to the RFC that was understood as a follow-up from the original stabilization.
## What is stabilized?
Users may write `+ use<'a, T>` bounds on their RPITITs. This conceptually modifies the desugaring of the RPITIT to omit the lifetimes that we would copy over from the method. For example,
```rust
trait Foo {
fn method<'a>(&'a self) -> impl Sized;
// ... desugars to something like:
type RPITIT_1<'a>: Sized;
fn method_desugared<'a>(&'a self) -> Self::RPITIT_1<'a>;
// ... whereas with precise capturing ...
fn precise<'a>(&'a self) -> impl Sized + use<Self>;
// ... desugars to something like:
type RPITIT_2: Sized;
fn precise_desugared<'a>(&'a self) -> Self::RPITIT_2;
}
```
And thus the GAT doesn't name `'a`. In the compiler internals, it's not implemented exactly like this, but not in a way that users should expect to be able to observe.
#### Limitations on what generics must be captured
Currently, we require that all generics from the trait (including the `Self`) type are captured. This is because the generics from the trait are required to be *invariant* in order to do associated type normalization.
And like regular precise capturing bounds, all type and const generics in scope must be captured.
Thus, only the in-scope method lifetimes may be relaxed with this syntax today.
## What isn't stabilized? (a.k.a. potential future work)
See section above. Relaxing the requirement to capture all type and const generics in scope may be relaxed when https://github.com/rust-lang/rust/issues/130043 is implemented, however it currently interacts with some underexplored corners of the type system (e.g. unconstrained type bivariance) so I don't expect it to come soon after.
## Implementation summary
This functionality is implemented analogously to the way that *opaque type* precise capturing works.
Namely, we currently use *variance* to model the capturedness of lifetimes. However, since RPITITs are anonymous GATs instead of opaque types, we instead modify the type relation of GATs to consider variances for RPITITs (along with opaque types which it has done since https://github.com/rust-lang/rust/pull/103491).
https://github.com/rust-lang/rust/blob/30f168ef811aec63124eac677e14699baa9395bd/compiler/rustc_middle/src/ty/util.rs#L954-L976
https://github.com/rust-lang/rust/blob/30f168ef811aec63124eac677e14699baa9395bd/compiler/rustc_type_ir/src/relate.rs#L240-L244
Using variance to model capturedness is an implementation detail, and in the future it would be desirable if opaques and RPITITs simply did not include the uncaptured lifetimes in their generics. This can be changed in a forwards-compatible way, and almost certainly would not be observable by users (at least not negatively, since it may indeed fix some bugs along the way).
## Tests
* Test that the lifetime isn't actually captured: `tests/ui/impl-trait/precise-capturing/rpitit.rs` and `tests/ui/impl-trait/precise-capturing/rpitit-outlives.rs` and `tests/ui/impl-trait/precise-capturing/rpitit-outlives-2.rs`.
* Technical test for variance computation: `tests/ui/impl-trait/in-trait/variance.rs`.
* Test that you must capture all trait generics: `tests/ui/impl-trait/precise-capturing/forgot-to-capture-type.rs`.
* Test that you cannot capture more than what the trait specifies: `tests/ui/impl-trait/precise-capturing/rpitit-captures-more-method-lifetimes.rs` and `tests/ui/impl-trait/precise-capturing/rpitit-impl-captures-too-much.rs`.
* Undercapturing (refinement) lint: `tests/ui/impl-trait/in-trait/refine-captures.rs`.
### What other unstable features may be exposed by this feature?
I don't believe that this exposes any new unstable features indirectly.
## Remaining bugs and open issues
Not aware of any open issues or bugs.
## Tooling support
Rustfmt: :white_check_mark: Supports formatting `+ use<>` everywhere.
Clippy: :white_check_mark: No support needed, unless specific clippy lints are impl'd to care for precise capturing itself.
Rustdoc: :white_check_mark: Rendering `+ use<>` precise capturing bounds is supported.
Rust-analyzer: :white_check_mark: Parser support, and then lifetime support isn't needed https://github.com/rust-lang/rust/pull/138128#issuecomment-2705292494 (previous: ~~:question: There is parser support, but I am unsure of rust-analyzer's level of support for RPITITs in general.~~)
## History
Tracking issue: https://github.com/rust-lang/rust/issues/130044
* https://github.com/rust-lang/rust/pull/131033
* https://github.com/rust-lang/rust/pull/132795
* https://github.com/rust-lang/rust/pull/136554
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Visitors track whether an assoc item is in a trait impl or an inherent impl
`AssocCtxt::Impl` now contains an `of_trait` field. This allows ast lowering and nameres to not have to track whether we're in a trait impl or an inherent impl.
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Add a helper for building an owner id in ast lowering
Just some deduplication of owner-id creations. Will also help me later split up ast lowering into per-owner queries, as it won't be possible anymore to go from a NodeId to a DefId of an owner without doing extra work to check whether we have an owner id. So I'd just do that in the new `owner_id` function and keep the `local_def_id` function free of that logic
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Parameter patterns are lowered to an `Ident` by
`lower_fn_params_to_names`, which is used when lowering bare function
types, trait methods, and foreign functions. Currently, there are two
exceptional cases where the lowered param can become an empty `Ident`.
- If the incoming pattern is an empty `Ident`. This occurs if the
parameter is anonymous, e.g. in a bare function type.
- If the incoming pattern is neither an ident nor an underscore. Any
such parameter will have triggered a compile error (hence the
`span_delayed_bug`), but lowering still occurs.
This commit replaces these empty `Ident` results with `None`, which
eliminates a number of `kw::Empty` uses, and makes it impossible to fail
to check for these exceptional cases.
Note: the `FIXME` comment in `is_unwrap_or_empty_symbol` is removed. It
actually should have been removed in #138482, the precursor to this PR.
That PR changed the lowering of wild patterns to `_` symbols instead of
empty symbols, which made the mentioned underscore check load-bearing.
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`LoweringContext::new_named_lifetime` lowers the `ident` passed in. Both
of its call sites *also* lower `ident` *before* passing it in. I.e. both
call sites cause the ident to be lowered twice. This commit removes the
lowering at the two call sites, so the ident is only lowered once.
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It has a single call site.
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Currently (PatKind::Wild` (i.e. `_`) gets turned by
`lower_fn_params_to_names` into an empty identifier, which means it is
printed incorrectly by HIR pretty printing.
And likewise for `lower_fn_params_to_names`, which affects some error
messages.
This commit fixes them. This requires a slight tweak in a couple of
places to continue using parameter numbers in some error messages. And
it improves the output of `tests/ui/typeck/cyclic_type_ice.rs`:
`/* _ */` is a better suggestion than `/* */`.
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Rollup of 7 pull requests
Successful merges:
- #137314 (change definitely unproductive cycles to error)
- #137701 (Convert `ShardedHashMap` to use `hashbrown::HashTable`)
- #138269 (uefi: fs: Implement FileType, FilePermissions and FileAttr)
- #138331 (Use `RUSTC_LINT_FLAGS` more)
- #138345 (Some autodiff cleanups)
- #138387 (intrinsics: remove unnecessary leading underscore from argument names)
- #138390 (fix incorrect tracing log)
r? `@ghost`
`@rustbot` modify labels: rollup
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r=onur-ozkan,jieyouxu
Use `RUSTC_LINT_FLAGS` more
An alternative to the failed #138084.
Fixes #138106.
r? ````@jieyouxu````
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Remove `NtItem` and `NtStmt`
Another piece of #124141.
r? `@petrochenkov`
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Add `#[define_opaques]` attribute and require it for all type-alias-impl-trait sites that register a hidden type
Instead of relying on the signature of items to decide whether they are constraining an opaque type, the opaque types that the item constrains must be explicitly listed.
A previous version of this PR used an actual attribute, but had to keep the resolved `DefId`s in a side table.
Now we just lower to fields in the AST that have no surface syntax, instead a builtin attribute macro fills in those fields where applicable.
Note that for convenience referencing opaque types in associated types from associated methods on the same impl will not require an attribute. If that causes problems `#[defines()]` can be used to overwrite the default of searching for opaques in the signature.
One wart of this design is that closures and static items do not have generics. So since I stored the opaques in the generics of functions, consts and methods, I would need to add a custom field to closures and statics to track this information. During a T-types discussion we decided to just not do this for now.
fixes #131298
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It's no longer necessary now that `-Wunreachable_pub` is being passed.
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Revert <https://github.com/rust-lang/rust/pull/138084> to buy time to
consider options that avoids breaking downstream usages of cargo on
distributed `rustc-src` artifacts, where such cargo invocations fail due
to inability to inherit `lints` from workspace root manifest's
`workspace.lints` (this is only valid for the source rust-lang/rust
workspace, but not really the distributed `rustc-src` artifacts).
This breakage was reported in
<https://github.com/rust-lang/rust/issues/138304>.
This reverts commit 48caf81484b50dca5a5cebb614899a3df81ca898, reversing
changes made to c6662879b27f5161e95f39395e3c9513a7b97028.
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Use workspace lints for crates in `compiler/`
This is nicer and hopefully less error prone than specifying lints via bootstrap.
r? ``@jieyouxu``
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(Except for `rustc_codegen_cranelift`.)
It's no longer necessary now that `unreachable_pub` is in the workspace
lints.
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It's clearer than using `kw::Empty` to mean `None`.
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This is temporarily needed for `x doc compiler` to work. They can be
removed once the `Nonterminal` is removed (#124141).
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Provide more context on resolve error caused from incorrect RTN
When encountering a resolve E0575 error for an associated method (when a type was expected), see if it could have been an intended return type notation bound.
```
error[E0575]: expected associated type, found associated function `Trait::method`
--> $DIR/bad-inputs-and-output.rs:31:36
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LL | fn foo_qualified<T: Trait>() where <T as Trait>::method(i32): Send {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^ not a associated type
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help: you might have meant to use the return type notation syntax
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LL - fn foo_qualified<T: Trait>() where <T as Trait>::method(i32): Send {}
LL + fn foo_qualified<T: Trait>() where T::method(..): Send {}
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```
Built on top of #137824, only second commit is relevant for review.
r? ````````@compiler-errors````````
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When `#![feature(min_generic_const_args)]` is enabled, we now lower all
const paths in generic arg position to `hir::ConstArgKind::Path`. We
then lower assoc const paths to `ty::ConstKind::Unevaluated` since we
can no longer use the anon const expression lowering machinery. In the
process of implementing this, I factored out `hir_ty_lowering` code that
is now shared between lowering assoc types and assoc consts.
This PR also introduces a `#[type_const]` attribute for trait assoc
consts that are allowed as const args. However, we still need to
implement code to check that assoc const definitions satisfy
`#[type_const]` if present (basically is it a const path or a
monomorphic anon const).
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When encountering a resolve E0575 error for an associated method (when a type was expected), see if it could have been an intended return type notation bound.
```
error[E0575]: expected associated type, found associated function `Trait::method`
--> $DIR/bad-inputs-and-output.rs:31:36
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LL | fn foo_qualified<T: Trait>() where <T as Trait>::method(i32): Send {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^ not a associated type
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help: you might have meant to use the return type notation syntax
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LL - fn foo_qualified<T: Trait>() where <T as Trait>::method(i32): Send {}
LL + fn foo_qualified<T: Trait>() where T::method(..): Send {}
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```
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Make suggestions verbose.
When encountering `method(type)` bound, suggest `method(..)` instead of `method()`.
```
error: argument types not allowed with return type notation
--> $DIR/bad-inputs-and-output.rs:9:23
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LL | fn foo<T: Trait<method(i32): Send>>() {}
| ^^^^^
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help: remove the input types
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LL - fn foo<T: Trait<method(i32): Send>>() {}
LL + fn foo<T: Trait<method(..): Send>>() {}
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```
When encountering both return type and arg list that isn't `..`, suggest replacing both.
```
error: return type not allowed with return type notation
--> $DIR/bad-inputs-and-output.rs:12:25
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LL | fn bar<T: Trait<method() -> (): Send>>() {}
| ^^^^^^
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help: use the right argument notation and remove the return type
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LL - fn bar<T: Trait<method() -> (): Send>>() {}
LL + fn bar<T: Trait<method(..): Send>>() {}
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```
When encountering a return type, suggest removing it including the leading whitespace.
```
error: return type not allowed with return type notation
--> $DIR/bad-inputs-and-output.rs:24:45
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LL | fn bay_path<T: Trait>() where T::method(..) -> (): Send {}
| ^^^^^
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help: remove the return type
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LL - fn bay_path<T: Trait>() where T::method(..) -> (): Send {}
LL + fn bay_path<T: Trait>() where T::method(..): Send {}
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```
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regressions
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note: compiler compiles but librustdoc and clippy don't
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fixup docs in parser
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The end goal is to eliminate `Map` altogether.
I added a `hir_` prefix to all of them, that seemed simplest. The
exceptions are `module_items` which became `hir_module_free_items` because
there was already a `hir_module_items`, and `items` which became
`hir_free_items` for consistency with `hir_module_free_items`.
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Rollup of 11 pull requests
Successful merges:
- #136606 (Fix long lines which rustfmt fails to format)
- #136663 (Stabilize `NonZero::count_ones`)
- #136672 (library: doc: core::alloc::Allocator: trivial typo fix)
- #136704 (Improve examples for file locking)
- #136721 (cg_llvm: Reduce visibility of some items outside the `llvm` module)
- #136813 (rustc_target: Add the fp16 target feature for AArch32)
- #136830 (fix i686-unknown-hurd-gnu x87 footnote)
- #136832 (Fix platform support table for i686-unknown-uefi)
- #136835 (Stop using span hack for contracts feature gating)
- #136837 (Overhaul how contracts are lowered on fn-like bodies)
- #136839 (fix ensure_monomorphic_enough)
r? `@ghost`
`@rustbot` modify labels: rollup
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