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Split Bound index into Canonical and Bound
See [#t-types/trait-system-refactor > perf `async-closures/post-mono-higher-ranked-hang.rs`](https://rust-lang.zulipchat.com/#narrow/channel/364551-t-types.2Ftrait-system-refactor/topic/perf.20.60async-closures.2Fpost-mono-higher-ranked-hang.2Ers.60/with/541535613) for context
Things compile and tests pass, but not sure if this actually solves the perf issue (edit: it does). Opening up this to do a perf (and maybe crater) run.
r? lcnr
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Allow specifying multiple bounds for same associated item, except in trait objects
Supersedes https://github.com/rust-lang/rust/pull/143146, fixes https://github.com/rust-lang/rust/issues/143143.
This PR proposes to stop enforcing E0719 in all contexts other than trait object types.
E0719 forbids constraining the same associated item twice within the same angle-bracket delimited associated item bound list (the `…` inside `T: Trait<…>`). For example, the following are forbidden:
| Forbidden | Working alternative |
|--------------------------------------------|--------------------------------------------------------------------|
| `T: Trait<Gat<u32> = u32, Gat<u64> = u64>` | `T: Trait<Gat<u32> = u32> + Trait<Gat<u64> = u64>` |
| `T: Iterator<Item = u32, Item = i32>` | `T: Iterator<Item = u32> + Iterator<Item = i32>` (trivially false) |
| `T: Iterator<Item = u32, Item = u32>` | `T: Iterator<Item = u32>` |
| `T: Iterator<Item: Send, Item: Sync>` | `T: Iterator<Item: Send + Sync>` |
| `T: Trait<ASSOC = 3, ASSOC = 4>` | `T: Trait<ASSOC = 3> + Trait<ASSOC = 4>` (trivially false) |
| `T: Trait<ASSOC = 3, ASSOC = 3>` | `T: Trait<ASSOC = 3>` |
With this PR, all those previously forbidden examples would start working, as well as their APIT and RPIT equivalents.
Types like `dyn Iterator<Item = u32, Item = u32>` will continue to be rejected, however. See https://github.com/rust-lang/rust/pull/143146#issuecomment-3274421752 for the reason why.
```@rustbot``` label T-lang T-types needs-fcp
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cmse: fix 'region variables should not be hashed'
tracking issue: https://github.com/rust-lang/rust/issues/81391
fixes https://github.com/rust-lang/rust/issues/131639
Some background: the `cmse-nonsecure-call` calling convention is used for a call from "secure" to "non-secure" code. To make sure that "non-secure" cannot read any secrets, restrictions are put on the signatures of functions with this calling convention: they can only use 4 arguments for passing arguments, and one register for passing a result. No arguments are passed via the stack, and all other registers are cleared before the call.
We check during `hir_ty_lowering` that the signature follows these rules. We do that by determining and then inspecting the layout of the type. That works well overall, but can run into asserts when the type itself is ill-formed. This PR fixes one such case.
I believe that the fix here, just erasing the regions, is the right shape, but there may be some nuance that I'm missing.
r? types
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Much of the compiler calls functions on Align projected from AbiAlign.
AbiAlign impls Deref to its inner Align, so we can simplify these away.
Also, it will minimize disruption when AbiAlign is removed.
For now, preserve usages that might resolve to PartialOrd or PartialEq,
as those have odd inference.
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Add an attribute to check the number of lanes in a SIMD vector after monomorphization
Allows std::simd to drop the `LaneCount<N>: SupportedLaneCount` trait and maintain good error messages.
Also, extends rust-lang/rust#145967 by including spans in layout errors for all ADTs.
r? ``@RalfJung``
cc ``@workingjubilee`` ``@programmerjake``
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monomorphization
Unify zero-length and oversized SIMD errors
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fix issue with `cmse-nonsecure-entry` ABI being both async and c-variadic
tracking issue: https://github.com/rust-lang/rust/issues/75835
fixes https://github.com/rust-lang/rust/issues/132142
An `extern "cmse-nonsecure-entry"` function cannot be c-variadic (or, in any case, clang/LLVM does not support it, see https://godbolt.org/z/MaPjzGcE1). So just stop looking at the type if we know it'll be invalid anyway.
I'm not entirely sure how to test this. The ICE is only possible on the `thumbv8m.main-none-eabi` and some related targets. I think using `minicore` is the most convenient, but use of `async` requires quite a long list of lang items to be present. Maybe we want that anyway though? On the other hand, it's extra `minicore` surface that might go out of date.
An alternative is `run-make`, that should work, but is much less convenient. See also [#t-compiler/help > `async fn` and `minicore`](https://rust-lang.zulipchat.com/#narrow/channel/182449-t-compiler.2Fhelp/topic/.60async.20fn.60.20and.20.60minicore.60/with/539427262).
r? `@ghost`
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Remove dead code stemming from an old effects desugaring
CC https://github.com/rust-lang/rust/pull/132374, https://github.com/rust-lang/rust/pull/133443.
r? fee1-dead
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Reject relaxed bounds inside associated type bounds (ATB)
**Reject** relaxed bounds — most notably `?Sized` — inside associated type bounds `TraitRef<AssocTy: …>`.
This was previously accepted without warning despite being incorrect: ATBs are *not* a place where we perform *sized elaboration*, meaning `TraitRef<AssocTy: …>` does *not* elaborate to `TraitRef<AssocTy: Sized + …>` if `…` doesn't contain `?Sized`. Therefore `?Sized` is meaningless. In no other (stable) place do we (intentionally) allow relaxed bounds where we don't also perform sized elab, this is highly inconsistent and confusing! Another point of comparison: For the desugared `$SelfTy: TraitRef, $SelfTy::AssocTy: …` we don't do sized elab either (and thus also don't allow relaxed bounds).
Moreover — as I've alluded to back in https://github.com/rust-lang/rust/pull/135841#pullrequestreview-2619462717 — some later validation steps only happen during sized elaboration during HIR ty lowering[^1]. Namely, rejecting duplicates (e.g., `?Trait + ?Trait`) and ensuring that `Trait` in `?Trait` is equal to `Sized`[^2]. As you can probably guess, on stable/master we don't run these checks for ATBs (so we allow even more nonsensical bounds like `Iterator<Item: ?Copy>` despite T-types's ruling established in the FCP'ed rust-lang/rust#135841).
This PR rectifies all of this. I cratered this back in 2025-01-10 with (allegedly) no regressions found ([report](https://github.com/rust-lang/rust/pull/135331#issuecomment-2585330783), [its analysis](https://github.com/rust-lang/rust/pull/135331#issuecomment-2585356422)). [However a contributor manually found two occurrences](https://github.com/rust-lang/rust/issues/135229#issuecomment-2581832852) of `TraitRef<AssocTy: ?Sized>` in small hobby projects (presumably via GH code search). I immediately sent downstream PRs: https://github.com/Gui-Yom/turbo-metrics/pull/14, https://github.com/ireina7/summon/pull/1 (however, the owners have showed no reaction so far).
I'm leaning towards banning these forms **without a FCW** because a FCW isn't worth the maintenance cost[^3]. Note that associated type bounds were stabilized in 1.79.0 (released 2024-06-13 which is 13 months ago), so the proliferation of ATBs shouldn't be that high yet. If you think we should do another crater run since the last one was 6 months ago, I'm fine with that.
Fixes rust-lang/rust#135229.
[^1]: I consider this a flaw in the implementation and [I've already added a huge FIXME](https://github.com/rust-lang/rust/blob/82a02aefe07092c737c852daccebf49ca25507e3/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs#L195-L207).
[^2]: To be more precise, if the internal flag `-Zexperimental-default-bounds` is provided other "default traits" (needs internal feature `lang_items`) are permitted as well (cc closely related internal feature: `more_maybe_bounds`).
[^3]: Having to track this and adding an entire lint whose remnants would remain in the code base forever (we never *fully* remove lints).
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Reduce indirect assoc parent queries
Simplify some code that uses multiple queries to get the parent of an associated item.
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`TyCtxt::short_string` ensures that user visible type paths aren't overwhelming on the terminal output, and properly saves the long name to disk as a side-channel. We already use these throughout the compiler and have been using them as needed when users find cases where the output is verbose. This is a proactive search of some cases to use `short_string`.
We add support for shortening the path of "trait path only".
Every manual use of `short_string` is a bright marker that that error should be using structured diagnostics instead (as they have proper handling of long types without the maintainer having to think abou tthem).
When we don't actually print out a shortened type we don't need the "use `--verbose`" note.
On E0599 show type identity to avoid expanding the receiver's generic parameters.
Unify wording on `long_ty_path` everywhere.
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Distinguish prepending and replacing self ty in predicates
There are two kinds of functions called `with_self_ty`:
1. Prepends the `Self` type onto an `ExistentialPredicate` which lacks it in its internal representation.
2. Replaces the `Self` type of an existing predicate, either for diagnostics purposes or in the new trait solver when normalizing that self type.
This PR distinguishes these two because I often want to only grep for one of them. Namely, let's call it `with_replaced_self_ty` when all we're doing is replacing the self type.
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Improve bound const handling
A few changes to make const handling more similar to type handling.
r? `@compiler-errors` -errors
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There are identical definitions in `rustc_type_ir` and `rustc_ast`. This
commit removes them and places a single definition in `rustc_ast_ir`.
This requires adding `rust_span` as a dependency of `rustc_ast_ir`, but
means a bunch of silly conversion functions can be removed.
The one annoying wrinkle is that the old version had differences in
their `Debug` impls, e.g. one printed `u32` while the other printed
`U32`. Some compiler error messages rely on the former (yuk), and some
clippy output depends on the latter. So the commit also changes clippy
to not rely on `Debug` and just implement what it needs itself.
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Currently there is `Ty` and `BoundTy`, and `Region` and `BoundRegion`,
and `Const` and... `BoundVar`. An annoying inconsistency.
This commit repurposes the existing `BoundConst`, which was barely used,
so it's the partner to `Const`. Unlike `BoundTy`/`BoundRegion` it lacks
a `kind` field but it's still nice to have because it makes the const
code more similar to the ty/region code everywhere.
The commit also removes `impl From<BoundVar> for BoundTy`, which has a
single use and doesn't seem worth it.
These changes fix the "FIXME: We really should have a separate
`BoundConst` for consts".
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Add implicit sized bound to trait ascription types
r? ```@fmease``` or reassign
Thanks for catching this :)
Fixes rust-lang/rust#144135
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Rollup of 10 pull requests
Successful merges:
- rust-lang/rust#141076 (fix Zip unsoundness (again))
- rust-lang/rust#142444 (adding run-make test to autodiff)
- rust-lang/rust#143704 (Be a bit more careful around exotic cycles in in the inliner)
- rust-lang/rust#144073 (Don't test panic=unwind in panic_main.rs on Fuchsia)
- rust-lang/rust#144083 (miri sleep tests: increase slack)
- rust-lang/rust#144092 (bootstrap: Detect musl hosts)
- rust-lang/rust#144098 (Do not lint private-in-public for RPITIT)
- rust-lang/rust#144103 (Rename `emit_unless` to `emit_unless_delay`)
- rust-lang/rust#144108 (Ignore tests/run-make/link-eh-frame-terminator/rmake.rs when cross-compiling)
- rust-lang/rust#144115 (fix outdated comment)
r? `@ghost`
`@rustbot` modify labels: rollup
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Signed-off-by: xizheyin <xizheyin@smail.nju.edu.cn>
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Having multiple relaxed bounds like `?Sized + ?Iterator` is actually *fine*.
We actually want to reject *duplicate* relaxed bounds like `?Sized + ?Sized`
because these most certainly represent a user error.
Note that this doesn't mean that we accept more code because a bound like
`?Iterator` is still invalid as it's not relaxing a *default* trait and
the only way to define / use more default bounds is under the experimental
and internal feature `more_maybe_bounds` plus `lang_items` plus unstable
flag `-Zexperimental-default-bounds` (historical context: for the longest
time, bounds like `?Iterator` were actually allowed and lead to a hard
warning).
Ultimately, this simply *reframes* the diagnostic. The scope of
`more_maybe_bounds` / `-Zexperimental-default-bounds` remains unchanged
as well.
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* The phrasing "only does something for" made sense back when this
diagnostic was a (hard) warning. Now however, it's simply a hard
error and thus completely rules out "doing something".
* The primary message was way too long
* The new wording more closely mirrors the wording we use for applying
other bound modifiers (like `const` and `async`) to incompatible
traits.
* "all other traits are not bound by default" is no longer accurate
under Sized Hierarchy. E.g., traits and assoc tys are (currently)
bounded by `MetaSized` by default but can't be relaxed using
`?MetaSized` (instead, you relax it by adding `PointeeSized`).
* I've decided against adding any diagnositic notes or suggestions
for now like "trait `Trait` can't be relaxed as it's not bound by
default" which would be incorrect for `MetaSized` and assoc tys
as mentioned above) or "consider changing `?MetaSized` to
`PointeeSized`" as the Sized Hierarchy impl is still WIP)
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Only relevant to the internal feature `more_maybe_bounds`.
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Fix some comments and related types and locals where it is obvious, e.g.
- bare_fn -> fn_ptr
- LifetimeBinderKind::BareFnType -> LifetimeBinderKind::FnPtrType
Co-authored-by: León Orell Valerian Liehr <me@fmease.dev>
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