Add support for `cfg(overflow_checks)`
This PR adds support for detecting if overflow checks are enabled in similar fashion as `debug_assertions` are detected. Possible use-case of this, for example, if we want to use checked integer casts in builds with overflow checks, e.g.
```rust
pub fn cast(val: usize)->u16 {
if cfg!(overflow_checks) {
val.try_into().unwrap()
}
else{
vas as _
}
}
```
Resolves#91130.
Require impl Trait in associated types to appear in method signatures
This implements the limited version of TAIT that was proposed in https://github.com/rust-lang/rust/issues/107645#issuecomment-1477899536
Similar to `impl Trait` in return types, `impl Trait` in associated types may only be used within the impl block which it is a part of. To make everything simpler and forward compatible to getting desugared to a plain type alias impl trait in the future, we're requiring that any associated functions or constants that want to register hidden types must be using the associated type in their signature (type of the constant or argument/return type of the associated method. Where bounds mentioning the associated type are ignored).
We have preexisting tests checking that this works transitively across multiple associated types in situations like
```rust
impl Foo for Bar {
type A = impl Trait;
type B = impl Iterator<Item = Self::A>;
fn foo() -> Self::B { ...... }
}
```
Reduce BitSet size used in `Borrows` dataflow analysis
It looks like it is not needed to multiply the number of borrows by 2. Bits greater than `self.borrow_set.len()` are never set in this bitset. This should decrease the memory usage by an epsilon.
Uplift `clippy::{drop,forget}_{ref,copy}` lints
This PR aims at uplifting the `clippy::drop_ref`, `clippy::drop_copy`, `clippy::forget_ref` and `clippy::forget_copy` lints.
Those lints are/were declared in the correctness category of clippy because they lint on useless and most probably is not what the developer wanted.
## `drop_ref` and `forget_ref`
The `drop_ref` and `forget_ref` lint checks for calls to `std::mem::drop` or `std::mem::forget` with a reference instead of an owned value.
### Example
```rust
let mut lock_guard = mutex.lock();
std::mem::drop(&lock_guard) // Should have been drop(lock_guard), mutex
// still locked
operation_that_requires_mutex_to_be_unlocked();
```
### Explanation
Calling `drop` or `forget` on a reference will only drop the reference itself, which is a no-op. It will not call the `drop` or `forget` method on the underlying referenced value, which is likely what was intended.
## `drop_copy` and `forget_copy`
The `drop_copy` and `forget_copy` lint checks for calls to `std::mem::forget` or `std::mem::drop` with a value that derives the Copy trait.
### Example
```rust
let x: i32 = 42; // i32 implements Copy
std::mem::forget(x) // A copy of x is passed to the function, leaving the
// original unaffected
```
### Explanation
Calling `std::mem::forget` [does nothing for types that implement Copy](https://doc.rust-lang.org/std/mem/fn.drop.html) since the value will be copied and moved into the function on invocation.
-----
Followed the instructions for uplift a clippy describe here: https://github.com/rust-lang/rust/pull/99696#pullrequestreview-1134072751
cc `@m-ou-se` (as T-libs-api leader because the uplifting was discussed in a recent meeting)
use by ref TokenTree iterator to avoid a few clones
Just a handful of swaps from the by-value cursor to by-ref cursor so as to avoid some unnecessary clones.
I've been doing some analysis on internal cleanup opportunities within rustfmt and as part of that yak-shave I found myself perusing broader token stream and tree usage (which we use within rustfmt). As reflected in some inline comments on the cursor structs (not part of this diff), there's probably many other such cases throughout the code, but figured I'd start small with these while I had the time. May take a look at the other sites in the future
Don't ICE in layout computation for placeholder types
We use `layout_of` for the built-in `PointerLike` trait to check if a type can be coerced to a `dyn*`.
Since the new solver canonicalizes parameter types to placeholders, that code needs to be able to treat placeholders like params, and for the most part it does, **except** for a call to `is_trivially_sized`. This PR fixes that.
Verify copies of mutable pointers in 2 stages in ReferencePropagation
Fixes#111422
In the first stage, we mark the copies as reborrows, to be checked later.
In the second stage, we walk the reborrow chains to verify that all stages are fully replacable.
The replacement itself mirrors the check, and iterates through the reborrow chain.
r? ``````@RalfJung``````
cc ``````@JakobDegen``````
bump windows crate 0.46 -> 0.48
This drops duped version of crate(0.46), reduces `rustc_driver.dll` ~800kb and reduces exported functions number from 26k to 22k.
Also while here, added `tidy-alphabetical` sorting to lists in tidy allowed lists.
CFI: Fix SIGILL reached via trait objects
Fix#106547 by transforming the concrete self into a reference to a trait object before emitting type metadata identifiers for trait methods.
use implied bounds when checking opaque types
During opaque type inference, we check for the well-formedness of the hidden type in the opaque type's own environment, not the one of the defining site, which are different in the case of TAIT.
However in the case of associated-type-impl-trait, we don't use implied bounds from the impl header. This caused us to reject the following:
```rust
trait Service<Req> {
type Output;
fn call(req: Req) -> Self::Output;
}
impl<'a, Req> Service<&'a Req> for u8 {
type Output= impl Sized; // we can't prove WF of hidden type `WF(&'a Req)` although it's implied by the impl
//~^ ERROR type parameter Req doesn't live long enough
fn call(req: &'a Req) -> Self::Output {
req
}
}
```
although adding an explicit bound would make it pass:
```diff
- impl<'a, Req> Service<&'a Req> for u8 {
+ impl<'a, Req> Service<&'a Req> for u8 where Req: 'a, {
```
I believe it should pass as we already allow the concrete type to be used:
```diff
impl<'a, Req> Service<&'a Req> for u8 {
- type Output= impl Sized;
+ type Output= &'a Req;
```
Fixes#95922
Builds on #105982
cc ``@lcnr`` (because implied bounds)
r? ``@oli-obk``
This PR adds support for detecting if overflow checks are enabled in similar fashion as debug_assertions are detected.
Possible use-case of this, for example, if we want to use checked integer casts in builds with overflow checks, e.g.
```rust
pub fn cast(val: usize)->u16 {
if cfg!(overflow_checks) {
val.try_into().unwrap()
}
else{
vas as _
}
}
```
Resolves#91130.
Tracking issue: #111466.
Shrink `SelectionError` a lot
`SelectionError` used to be 80 bytes (on 64 bit). That's quite big. Especially because the selection cache contained `Result<_, SelectionError>. The Ok type is only 32 bytes, so the 80 bytes significantly inflate the size of the cache.
Most variants of the `SelectionError` seem to be hard errors, only `Unimplemented` shows up in practice (for cranelift-codegen, it occupies 23.4% of all cache entries). We can just box away the biggest variant, `OutputTypeParameterMismatch`, to get the size down to 16 bytes, well within the size of the Ok type inside the cache.
Isolate coverage FFI type layouts from their underlying LLVM C++ types
I noticed that several of the types used to send coverage information through FFI are not properly isolated from the layout of their corresponding C++ types in the LLVM API.
This PR adds more explicitly-defined FFI struct/enum types in `CoverageMappingWrapper.cpp`, so that Rust source files in `rustc_codegen_ssa` and `rustc_codegen_llvm` aren't directly exposed to LLVM C++ types.
Fix mishandled `--check-cfg` arguments order
This PR fixes a bug in `--check-cfg` where the order of `--check-cfg=names(a)` and `--check-cfg=values(a,…)` would trip the compiler.
Fixes https://github.com/rust-lang/rust/issues/111291
cc `@taiki-e` `@petrochenkov`
Prevent ICE with broken borrow in closure
r? `@Nilstrieb`
Fixes#108683
This solution isn't ideal, I'm hoping to find a way to continue compilation without ICEing.
Optimize dataflow-const-prop place-tracking infra
Optimization opportunities found while investigating https://github.com/rust-lang/rust/pull/110719
Computing places breadth-first ensures that we create short projections before deep projections, since the former are more likely to be propagated.
The most relevant is the pre-computation of flooded places. Callgrind showed `flood_*` methods and especially `preorder_preinvoke` were especially hot. This PR attempts to pre-compute the set of `ValueIndex` that `preorder_invoke` would visit.
Using this information, we make some `PlaceIndex` inaccessible when they contain no `ValueIndex`, allowing to skip computations for those places.
cc `@jachris` as original author
Switch to `EarlyBinder` for `thir_abstract_const` query
Part of the work to finish https://github.com/rust-lang/rust/issues/105779.
This PR adds `EarlyBinder` to the return type of the `thir_abstract_const` query and removes `bound_abstract_const`.
r? `@compiler-errors`
Encode types in SMIR
The first commit makes sure we can actually store a Ty<'tcx> (with the lifetime) in the thread local and get it back out. The second commit then introduces types.
r? `@spastorino`
Make alias bounds sound in the new solver (take 2)
Make alias bounds sound in the new solver (in a way that does not require coinduction) by only considering them for projection types whose corresponding trait refs come from a param-env candidate.
That is, given `<T as Trait>::Assoc: Bound`, we only *really* need to consider the alias bound if `T: Trait` is satisfied via a param-env candidate. If it's instead satisfied, e.g., via an user provided impl candidate or a , then that impl should have a concrete type to which we could otherwise normalize `<T as Trait>::Assoc`, and that concrete type is then responsible to prove the `Bound` on it.
Similar consideration is given to opaque types, since we only need to consider alias bounds if we're *not* in reveal-all mode, since similarly we'd be able to reveal the opaque types and prove any bounds that way.
This does not remove that hacky "eager projection replacement" logic from object bounds, which are somewhat like alias bounds. But removing this eager normalization behavior (added in #108333) would require full coinduction to be enabled. Compare to #110628, which does remove this object-bound custom logic but requires coinduction to be sound.
r? `@lcnr`
Support linking to rust dylib with --crate-type staticlib
This allows for example dynamically linking libstd, while statically linking the user crate into an executable or C dynamic library. For this two unstable flags (`-Z staticlib-allow-rdylib-deps` and `-Z staticlib-prefer-dynamic`) are introduced. Without the former you get an error. The latter is the equivalent to `-C prefer-dynamic` for the staticlib crate type to indicate that dynamically linking is preferred when both options are available, like for libstd. Care must be taken to ensure that no crate ends up being merged into two distinct staticlibs that are linked together. Doing so will cause a linker error at best and undefined behavior at worst. In addition two distinct staticlibs compiled by different rustc may not be combined under any circumstances due to some rustc private symbols not being mangled.
To successfully link a staticlib, `--print native-static-libs` can be used while compiling to ask rustc for the linker flags necessary when linking the staticlib. This is an existing flag which previously only listed native libraries. It has been extended to list rust dylibs too. Trying to locate libstd yourself to link against it is not supported and may break if for example the libstd of multiple rustc versions are put in the same directory.
For an example on how to use this see the `src/test/run-make-fulldeps/staticlib-dylib-linkage/` test.
Implement SSA-based reference propagation
Rust has a tendency to create a lot of short-lived borrows, in particular for method calls. This PR aims to remove those short-lived borrows with a const-propagation dedicated to pointers to local places.
This pass aims to transform the following pattern:
```
_1 = &raw? mut? PLACE;
_3 = *_1;
_4 = &raw? mut? *_1;
```
Into
```
_1 = &raw? mut? PLACE;
_3 = PLACE;
_4 = &raw? mut? PLACE;
```
where `PLACE` is a direct or an indirect place expression.
By removing indirection, this pass should help both dest-prop and const-prop to handle more cases.
This optimization is distinct from const-prop and dataflow const-prop since the borrow-reborrow patterns needs to preserve borrowck invariants, especially the uniqueness property of mutable references.
The pointed-to places are computed using a SSA analysis. We suppose that removable borrows are typically temporaries from autoref, so they are by construction assigned only once, and a SSA analysis is enough to catch them. For each local, we store both where and how it is used, in order to efficiently compute the all-or-nothing property. Thanks to `Derefer`, we only have to track locals, not places in general.
---
There are 3 properties that need to be upheld for this transformation to be legal:
- place constness: `PLACE` must refer to the same memory wherever it appears;
- pointer liveness: we must not introduce dereferences of dangling pointers;
- `&mut` borrow uniqueness.
## Constness
If `PLACE` is an indirect projection, if its of the form `(*LOCAL).PROJECTIONS` where:
- `LOCAL` is SSA;
- all projections in `PROJECTIONS` are constant (no dereference and no indexing).
If `PLACE` is a direct projection of a local, we consider it as constant if:
- the local is always live, or it has a single `StorageLive` that dominates all uses;
- all projections are constant.
# Liveness
When performing a substitution, we must take care not to introduce uses of dangling locals.
Using a dangling borrow is UB. Therefore, we assume that for any use of `*x`, where `x` is a borrow, the pointed-to memory is live.
Limitations:
- occurrences of `*x` in an `&raw mut? *x` are accepted;
- raw pointers are allowed to be dangling.
In those 2 case, we do not substitute anything, to be on the safe side.
**Open question:** we do not differentiate borrows of ZST and non-ZST. The UB rules may be
different depending on the layout. Having a different treatment would effectively prevent this
pass from running on polymorphic MIR, which defeats the purpose of MIR opts.
## Uniqueness
For `&mut` borrows, we also need to preserve the uniqueness property:
we must avoid creating a state where we interleave uses of `*_1` and `_2`.
To do it, we only perform full substitution of mutable borrows:
we replace either all or none of the occurrences of `*_1`.
Some care has to be taken when `_1` is copied in other locals.
```
_1 = &raw? mut? _2;
_3 = *_1;
_4 = _1
_5 = *_4
```
In such cases, fully substituting `_1` means fully substituting all of the copies.
For immutable borrows, we do not need to preserve such uniqueness property,
so we perform all the possible substitutions without removing the `_1 = &_2` statement.
Various changes to name resolution of anon consts
Sorry this PR is kind of all over the place ^^'
Fixes#111012
- Rewrites anon const nameres to all go through `fn resolve_anon_const` explicitly instead of `visit_anon_const` to ensure that we do not accidentally resolve anon consts as if they are allowed to use generics when they aren't. Also means that we dont have bits of code for resolving anon consts that will get out of sync (i.e. legacy const generics and resolving path consts that were parsed as type arguments)
- Renames two of the `LifetimeRibKind`, `AnonConst -> ConcreteAnonConst` and `ConstGeneric -> ConstParamTy`
- Noticed while doing this that under `generic_const_exprs` all lifetimes currently get resolved to errors without any error being emitted which was causing a bunch of tests to pass without their bugs having been fixed, incidentally fixed that in this PR and marked those tests as `// known-bug:`. I'm fine to break those since `generic_const_exprs` is a very unstable incomplete feature and this PR _does_ make generic_const_exprs "less broken" as a whole, also I can't be assed to figure out what the underlying causes of all of them are. This PR reopens#77357#83993
- Changed `generics_of` to stop providing generics and predicates to enum variant discriminant anon consts since those are not allowed to use generic parameters
- Updated the error for non 'static lifetime in const arguments and the error for non 'static lifetime in const param tys to use `derive(Diagnostic)`
I have a vague idea why const-arg-in-const-arg.rs, in-closure.rs and simple.rs have started failing which is unfortunate since these were deliberately made to work, I think lifetime resolution being broken just means this regressed at some point and nobody noticed because the tests were not testing anything :( I'm fine breaking these too for the same reason as the tests for #77357#83993. I couldn't get `// known-bug` to work for these ICEs and just kept getting different stderr between CI and local `--bless` so I just removed them and will create an issue to track re-adding (and fixing) the bugs if this PR lands.
r? `@cjgillot` cc `@compiler-errors`
Revert "Populate effective visibilities in `rustc_privacy`"
This reverts commit cff85f22f5, cc #110907. It needs to be fixed, but there are too many issues being reported that I wanted to put up a revert until a proper fix can be committed.
Fixes a ton of issues where private but still reachable impls were missing during codegen:
Fixes#111320Fixes#111321Fixes#111334Fixes#111357Fixes#111368Fixes#111373Fixes#111377Fixes#111386Fixes#111387
`@bors` p=1
r? `@petrochenkov`
This trait ref is derived from the self type and then equated to the
trait ref from the obligation.
For example, for `fn(): Fn(u32)`, `self_ty_trait_ref` is `Fn()`, which
is then equated to `Fn(u32)` (which will fail, causing the obligation to
fail).
`SelectionError` used to be 80 bytes (on 64 bit). That's quite big.
Especially because the selection cache contained `Result<_,
SelectionError>. The Ok type is only 32 bytes, so the 80 bytes
significantly inflate the size of the cache.
Most variants of the `SelectionError` seem to be hard errors, only
`Unimplemented` shows up in practice (for cranelift-codegen, it occupies
23.4% of all cache entries). We can just box away the biggest variant,
`OutputTypeParameterMismatch`, to get the size down to 16 bytes, well
within the size of the Ok type inside the cache.
Min specialization improvements
- Don't allow specialization impls with no items, such implementations are probably not correct and only occur as mistakes in the compiler and standard library
- Fix a missing normalization call
- Adds spans for lifetime errors from overly general specializations
Closes#79457Closes#109815
Implement builtin # syntax and use it for offset_of!(...)
Add `builtin #` syntax to the parser, as well as a generic infrastructure to support both item and expression position builtin syntaxes. The PR also uses this infrastructure for the implementation of the `offset_of!` macro, added by #106934.
cc `@petrochenkov` `@DrMeepster`
cc #110680 `builtin #` tracking issue
cc #106655 `offset_of!` tracking issue
tweak "make mut" spans when assigning to locals
Work towards fixing #106857
This PR just cleans up a lot of spans which is helpful before properly fixing the issues. Best reviewed commit-by-commit.
r? `@estebank`
Tweak borrow suggestion span
Avoids a `span_to_snippet` call when we don't need to surround the expression in parentheses. The fact that the suggestion was using the whole span of the expression rather than just appending a `&` was prevented me from using `// run-rustfix` in another PR (https://github.com/rust-lang/rust/pull/110432#discussion_r1170500484).
Also some drive-by renames of functions that have been annoying me for a bit.
Add GNU Property Note
Fix#103001
Generates the missing property note:
```
Displaying notes found in: .note.gnu.property
Owner Data size Description
GNU 0x00000010 NT_GNU_PROPERTY_TYPE_0 Properties: x86 feature: IBT
```
Rollup of 6 pull requests
Successful merges:
- #104070 (Prevent aborting guard from aborting the process in a forced unwind)
- #109410 (Introduce `AliasKind::Inherent` for inherent associated types)
- #111004 (Migrate `mir_transform` to translatable diagnostics)
- #111118 (Suggest struct when we get colon in fileds in enum)
- #111170 (Diagnostic args are still args if they're documented)
- #111354 (Fix miscompilation when calling default methods on `Future`)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Disable nrvo mir opt
See #111005 and #110902 . The ICE can definitely be hit on stable, the miscompilation I'm not sure about. The pass makes some pretty sketchy assumptions though, and we should not have it on while that's the case.
I'm not going to work on actually fixing this, it's probably not excessively difficult though.
r? rust-lang/mir-opt
Fix miscompilation when calling default methods on `Future`
In https://github.com/rust-lang/rust/issues/111264 I discovered a lingering miscompilation when calling a default method on `Future` (none currently exist). https://github.com/rust-lang/rust/pull/111279 added a debug assertion, which sadly doesn't help much since to my knowledge stage0 is not built with them enabled, and it still doesn't make default methods work like they should.
This PR fixes `resolve_instance` to resolve default methods on `Future` correctly, allowing library contributors to add `Future` combinators without running into ICEs or miscompilations. I've tested this as part of https://github.com/rust-lang/rust/pull/111347, but no test is included here (assuming that future methods include their own tests that would cover this sufficiently).
r? `@compiler-errors`
Introduce `AliasKind::Inherent` for inherent associated types
Allows us to check (possibly generic) inherent associated types for well-formedness.
Type inference now also works properly.
Follow-up to #105961. Supersedes #108430.
Fixes#106722.
Fixes#108957.
Fixes#109768.
Fixes#109789.
Fixes#109790.
~Not to be merged before #108860 (`AliasKind::Weak`).~
CC `@jackh726`
r? `@compiler-errors`
`@rustbot` label T-types F-inherent_associated_types
ConstProp into PlaceElem::Index.
Noticed this while looking at keccak output MIR.
This pass aims to replace `ProjectionElem::Index` with `ProjectionElem::ConstantIndex` during ConstProp.
r? `@ghost`
Mark s390x condition code register as clobbered in inline assembly
Various s390x instructions (arithmetic operations, logical operations, comparisons, etc. see also "Condition Codes" section in [z/Architecture Reference Summary](https://www.ibm.com/support/pages/zarchitecture-reference-summary)) modify condition code register `cc`, but AFAIK there is currently no way to mark it as clobbered in `asm!`.
`cc` register definition in LLVM:
https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/SystemZ/SystemZRegisterInfo.td#L320
This PR also updates asm_experimental_arch docs in the unstable-book to mention s390x registers.
cc `@uweigand`
r? `@Amanieu`
Don't compute trait super bounds unless they're positive
Fixes#111207
The comment is modified to explain the rationale for why we even have this recursive call to supertraits in the first place, which doesn't apply to negative bounds since they don't elaborate at all.
STD support for PSVita
This PR adds std support for `armv7-sony-vita-newlibeabihf` target.
The work here is fairly similar to #95897, just for a different target platform.
This depends on the following pull requests:
rust-lang/backtrace-rs#523rust-lang/libc#3209
Update max_atomic_width of armv7r and armv7_sony_vita targets to 64.
All armv7a and armv7r implementations support `ldrexd`/`strexd`, only armv7m does not.
Rollup of 7 pull requests
Successful merges:
- #110297 (Make `(try_)subst_and_normalize_erasing_regions` take `EarlyBinder`)
- #110827 (Fix lifetime suggestion for type aliases with objects in them)
- #111022 (Use smaller ints for bitflags)
- #111056 (Fix some suggestions where a `Box<T>` is expected.)
- #111262 (Further normalize msvc-non-utf8-ouput)
- #111265 (Make generics_of has_self on RPITITs delegate to the opaque)
- #111323 (Give a more helpful error when running the rustc shim directly)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Make generics_of has_self on RPITITs delegate to the opaque
r? `@compiler-errors`
I couldn't come up with a test case and none of the ones in the `tests` folder is impacted by this change, but I still think is the right thing to do.
Michael, let me know if you have ideas on how to add a test that's affected by this change.
Fix some suggestions where a `Box<T>` is expected.
This fixes#111011, and also adds a suggestion for boxing a unit type when a `Box<T>` was expected and an empty block was found.
Fix lifetime suggestion for type aliases with objects in them
Fixes an issue identified in https://github.com/rust-lang/rust/issues/110761#issuecomment-1520678479
This suggestion, like many other borrowck suggestions, are very fragile and there are other ways to trigger strange behavior even after this PR, so this is just a small improvement and not a total rework 💀
Make `(try_)subst_and_normalize_erasing_regions` take `EarlyBinder`
Changes `subst_and_normalize_erasing_regions` and `try_subst_and_normalize_erasing_regions` to take `EarlyBinder<T>` instead of `T`.
(related to #105779)
This was suggested by `@BoxyUwU` in https://github.com/rust-lang/rust/pull/107753#discussion_r1105828139. After changing `type_of` to return `EarlyBinder`, there were several places where the binder was immediately skipped to call `tcx.subst_and_normalize_erasing_regions`, only for the binder to be reconstructed inside of that method.
r? `@BoxyUwU`
enable `rust_2018_idioms` lint group for doctests
With this change, `rust_2018_idioms` lint group will be enabled for compiler/libstd doctests.
Resolves#106086Resolves#99144
Signed-off-by: ozkanonur <work@onurozkan.dev>
We really shouldn't be naming functions `fn check_*` unless they're
doing *typechecking*. It's especially misleading when we're doing this
inside of HIR typeck.
Rename InstCombine to InstSimplify
```
╭ ➜ ben@archlinux:~/rust
╰ ➤ rg -i instcombine
src/doc/rustc-dev-guide/src/mir/optimizations.md
134:may have been misapplied. Examples of this are `InstCombine` and `ConstantPropagation`.
src/ci/docker/host-x86_64/disabled/dist-x86_64-haiku/llvm-config.sh
38: instcombine instrumentation interpreter ipo irreader lanai \
tests/codegen/slice_as_from_ptr_range.rs
4:// min-llvm-version: 15.0 (because this is a relatively new instcombine)
```
r? `@scottmcm`
Support return-type bounds on associated methods from supertraits
Support `T: Trait<method(): Bound>` when `method` comes from a supertrait, aligning it with the behavior of associated type bounds (both equality and trait bounds).
The only wrinkle is that I have to extend `super_predicates_that_define_assoc_type` to look for *all* items, not just `AssocKind::Ty`. This will also be needed to support `feature(associated_const_equality)` as well, which is subtly broken when it comes to supertraits, though this PR does not fix those yet. There's a slight chance there's a perf regression here, in which case I guess I could split it out into a separate query.
