Implement raw lifetimes and labels (`'r#ident`)
This PR does two things:
1. Reserve lifetime prefixes, e.g. `'prefix#lt` in edition 2021.
2. Implements raw lifetimes, e.g. `'r#async` in edition 2021.
This PR additionally extends the `keyword_idents_2024` lint to also check lifetimes.
cc `@traviscross`
r? parser
bypass linker configuration and cross target check for specific commands
Avoids configuring the linker and checking cross-target-specific tools unless necessary.
Resolves#128180
cc `@ChrisDenton`
Apple: Refactor deployment target version parsing
Refactor deployment target parsing to make it easier to do https://github.com/rust-lang/rust/pull/129342 (I wanted to make sure of all the places that `std::env::var` is called).
Specifically, my goal was to minimize the amount of target-specific configuration, so to that end I renamed the `opts` function that generates the `TargetOptions` to `base`, and made it return the LLVM target and `target_arch` too. In the future, I would like to move even more out of the target files and into `spec::apple`, as it makes it easier for me to maintain.
For example, this fixed a bug in `aarch64-apple-watchos`, which wasn't passing the deployment target as part of the LLVM triple. This (probably) fixes https://github.com/rust-lang/rust/issues/123582 and fixes https://github.com/rust-lang/rust/issues/107630.
We also now parse the patch version of deployment targets, allowing the user to specify e.g. `MACOSX_DEPLOYMENT_TARGET=10.12.6`.
Finally, this fixes the LLVM target name for visionOS, it should be `*-apple-xros` and not `*-apple-visionos`.
Since I have changed all the Apple targets here, I smoke-tested my changes by running the following:
```console
# Build each target
./x build library --target="aarch64-apple-darwin,aarch64-apple-ios,aarch64-apple-ios-macabi,aarch64-apple-ios-sim,aarch64-apple-tvos,aarch64-apple-tvos-sim,aarch64-apple-visionos,aarch64-apple-visionos-sim,aarch64-apple-watchos,aarch64-apple-watchos-sim,arm64_32-apple-watchos,arm64e-apple-ios,armv7k-apple-watchos,armv7s-apple-ios,i386-apple-ios,x86_64-apple-darwin,x86_64-apple-ios,x86_64-apple-ios-macabi,x86_64-apple-tvos,x86_64-apple-watchos-sim,x86_64h-apple-darwin"
# Test that we can still at least link basic projects
cargo new foobar && cd foobar && cargo +stage1 build --target=aarch64-apple-darwin --target=aarch64-apple-ios --target=aarch64-apple-ios-macabi --target=aarch64-apple-ios-sim --target=aarch64-apple-tvos --target=aarch64-apple-tvos-sim --target=aarch64-apple-visionos --target=aarch64-apple-visionos-sim --target=aarch64-apple-watchos --target=aarch64-apple-watchos-sim --target=arm64_32-apple-watchos --target=armv7s-apple-ios --target=i386-apple-ios --target=x86_64-apple-darwin --target=x86_64-apple-ios --target=x86_64-apple-ios-macabi --target=x86_64-apple-tvos --target=x86_64-apple-watchos-sim --target=x86_64h-apple-darwin
```
I couldn't build for the `arm64e-apple-darwin` target, the `armv7k-apple-watchos` and `arm64e-apple-ios` targets failed to link, and I know that the `i686-apple-darwin` target requires a bit of setup, but all of this is as it was before this PR.
r? thomcc
CC `@BlackHoleFox`
I would recommend using `rollup=never` when merging this, in case we need to bisect this later.
stabilize `-Znext-solver=coherence`
r? `@compiler-errors`
---
This PR stabilizes the use of the next generation trait solver in coherence checking by enabling `-Znext-solver=coherence` by default. More specifically its use in the *implicit negative overlap check*. The tracking issue for this is https://github.com/rust-lang/rust/issues/114862. Closes#114862.
## Background
### The next generation trait solver
The new solver lives in [`rustc_trait_selection::solve`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_trait_selection/src/solve/mod.rs) and is intended to replace the existing *evaluate*, *fulfill*, and *project* implementation. It also has a wider impact on the rest of the type system, for example by changing our approach to handling associated types.
For a more detailed explanation of the new trait solver, see the [rustc-dev-guide](https://rustc-dev-guide.rust-lang.org/solve/trait-solving.html). This does not stabilize the current behavior of the new trait solver, only the behavior impacting the implicit negative overlap check. There are many areas in the new solver which are not yet finalized. We are confident that their final design will not conflict with the user-facing behavior observable via coherence. More on that further down.
Please check out [the chapter](https://rustc-dev-guide.rust-lang.org/solve/significant-changes.html) summarizing the most significant changes between the existing and new implementations.
### Coherence and the implicit negative overlap check
Coherence checking detects any overlapping impls. Overlapping trait impls always error while overlapping inherent impls result in an error if they have methods with the same name. Coherence also results in an error if any other impls could exist, even if they are currently unknown. This affects impls which may get added to upstream crates in a backwards compatible way and impls from downstream crates.
Coherence failing to detect overlap is generally considered to be unsound, even if it is difficult to actually get runtime UB this way. It is quite easy to get ICEs due to bugs in coherence.
It currently consists of two checks:
The [orphan check] validates that impls do not overlap with other impls we do not know about: either because they may be defined in a sibling crate, or because an upstream crate is allowed to add it without being considered a breaking change.
The [overlap check] validates that impls do not overlap with other impls we know about. This is done as follows:
- Instantiate the generic parameters of both impls with inference variables
- Equate the `TraitRef`s of both impls. If it fails there is no overlap.
- [implicit negative]: Check whether any of the instantiated `where`-bounds of one of the impls definitely do not hold when using the constraints from the previous step. If a `where`-bound does not hold, there is no overlap.
- *explicit negative (still unstable, ignored going forward)*: Check whether the any negated `where`-bounds can be proven, e.g. a `&mut u32: Clone` bound definitely does not hold as an explicit `impl<T> !Clone for &mut T` exists.
The overlap check has to *prove that unifying the impls does not succeed*. This means that **incorrectly getting a type error during coherence is unsound** as it would allow impls to overlap: coherence has to be *complete*.
Completeness means that we never incorrectly error. This means that during coherence we must only add inference constraints if they are definitely necessary. During ordinary type checking [this does not hold](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=01d93b592bd9036ac96071cbf1d624a9), so the trait solver has to behave differently, depending on whether we're in coherence or not.
The implicit negative check only considers goals to "definitely not hold" if they could not be implemented downstream, by a sibling, or upstream in a backwards compatible way. If the goal is is "unknowable" as it may get added in another crate, we add an ambiguous candidate: [source](bea5bebf3d/compiler/rustc_trait_selection/src/solve/assembly/mod.rs (L858-L883)).
[orphan check]: fd80c02c16/compiler/rustc_trait_selection/src/traits/coherence.rs (L566-L579)
[overlap check]: fd80c02c16/compiler/rustc_trait_selection/src/traits/coherence.rs (L92-L98)
[implicit negative]: fd80c02c16/compiler/rustc_trait_selection/src/traits/coherence.rs (L223-L281)
## Motivation
Replacing the existing solver in coherence fixes soundness bugs by removing sources of incompleteness in the type system. The new solver separately strengthens coherence, resulting in more impls being disjoint and passing the coherence check. The concrete changes will be elaborated further down. We believe the stabilization to reduce the likelihood of future bugs in coherence as the new implementation is easier to understand and reason about.
It allows us to remove the support for coherence and implicit-negative reasoning in the old solver, allowing us to remove some code and simplifying the old trait solver. We will only remove the old solver support once this stabilization has reached stable to make sure we're able to quickly revert in case any unexpected issues are detected before then.
Stabilizing the use of the next-generation trait solver expresses our confidence that its current behavior is intended and our work towards enabling its use everywhere will not require any breaking changes to the areas used by coherence checking. We are also confident that we will be able to replace the existing solver everywhere, as maintaining two separate systems adds a significant maintainance burden.
## User-facing impact and reasoning
### Breakage due to improved handling of associated types
The new solver fixes multiple issues related to associated types. As these issues caused coherence to consider more types distinct, fixing them results in more overlap errors. This is therefore a breaking change.
#### Structurally relating aliases containing bound vars
Fixes https://github.com/rust-lang/rust/issues/102048. In the existing solver relating ambiguous projections containing bound variables is structural. This is *incomplete* and allows overlapping impls. These was mostly not exploitable as the same issue also caused impls to not apply when trying to use them. The new solver defers alias-relating to a nested goal, fixing this issue:
```rust
// revisions: current next
//[next] compile-flags: -Znext-solver=coherence
trait Trait {}
trait Project {
type Assoc<'a>;
}
impl Project for u32 {
type Assoc<'a> = &'a u32;
}
// Eagerly normalizing `<?infer as Project>::Assoc<'a>` is ambiguous,
// so the old solver ended up structurally relating
//
// (?infer, for<'a> fn(<?infer as Project>::Assoc<'a>))
//
// with
//
// ((u32, fn(&'a u32)))
//
// Equating `&'a u32` with `<u32 as Project>::Assoc<'a>` failed, even
// though these types are equal modulo normalization.
impl<T: Project> Trait for (T, for<'a> fn(<T as Project>::Assoc<'a>)) {}
impl<'a> Trait for (u32, fn(&'a u32)) {}
//[next]~^ ERROR conflicting implementations of trait `Trait` for type `(u32, for<'a> fn(&'a u32))`
```
A crater run did not discover any breakage due to this change.
#### Unknowable candidates for higher ranked trait goals
This avoids an unsoundness by attempting to normalize in `trait_ref_is_knowable`, fixing https://github.com/rust-lang/rust/issues/114061. This is a side-effect of supporting lazy normalization, as that forces us to attempt to normalize when checking whether a `TraitRef` is knowable: [source](47dd709bed/compiler/rustc_trait_selection/src/solve/assembly/mod.rs (L754-L764)).
```rust
// revisions: current next
//[next] compile-flags: -Znext-solver=coherence
trait IsUnit {}
impl IsUnit for () {}
pub trait WithAssoc<'a> {
type Assoc;
}
// We considered `for<'a> <T as WithAssoc<'a>>::Assoc: IsUnit`
// to be knowable, even though the projection is ambiguous.
pub trait Trait {}
impl<T> Trait for T
where
T: 'static,
for<'a> T: WithAssoc<'a>,
for<'a> <T as WithAssoc<'a>>::Assoc: IsUnit,
{
}
impl<T> Trait for Box<T> {}
//[next]~^ ERROR conflicting implementations of trait `Trait`
```
The two impls of `Trait` overlap given the following downstream crate:
```rust
use dep::*;
struct Local;
impl WithAssoc<'_> for Box<Local> {
type Assoc = ();
}
```
There a similar coherence unsoundness caused by our handling of aliases which is fixed separately in https://github.com/rust-lang/rust/pull/117164.
This change breaks the [`derive-visitor`](https://crates.io/crates/derive-visitor) crate. I have opened an issue in that repo: nikis05/derive-visitor#16.
### Evaluating goals to a fixpoint and applying inference constraints
In the old implementation of the implicit-negative check, each obligation is [checked separately without applying its inference constraints](bea5bebf3d/compiler/rustc_trait_selection/src/traits/coherence.rs (L323-L338)). The new solver instead [uses a `FulfillmentCtxt`](bea5bebf3d/compiler/rustc_trait_selection/src/traits/coherence.rs (L315-L321)) for this, which evaluates all obligations in a loop until there's no further inference progress.
This is necessary for backwards compatibility as we do not eagerly normalize with the new solver, resulting in constraints from normalization to only get applied by evaluating a separate obligation. This also allows more code to compile:
```rust
// revisions: current next
//[next] compile-flags: -Znext-solver=coherence
trait Mirror {
type Assoc;
}
impl<T> Mirror for T {
type Assoc = T;
}
trait Foo {}
trait Bar {}
// The self type starts out as `?0` but is constrained to `()`
// due to the where-clause below. Because `(): Bar` is known to
// not hold, we can prove the impls disjoint.
impl<T> Foo for T where (): Mirror<Assoc = T> {}
//[current]~^ ERROR conflicting implementations of trait `Foo` for type `()`
impl<T> Foo for T where T: Bar {}
fn main() {}
```
The old solver does not run nested goals to a fixpoint in evaluation. The new solver does do so, strengthening inference and improving the overlap check:
```rust
// revisions: current next
//[next] compile-flags: -Znext-solver=coherence
trait Foo {}
impl<T> Foo for (u8, T, T) {}
trait NotU8 {}
trait Bar {}
impl<T, U: NotU8> Bar for (T, T, U) {}
trait NeedsFixpoint {}
impl<T: Foo + Bar> NeedsFixpoint for T {}
impl NeedsFixpoint for (u8, u8, u8) {}
trait Overlap {}
impl<T: NeedsFixpoint> Overlap for T {}
impl<T, U: NotU8, V> Overlap for (T, U, V) {}
//[current]~^ ERROR conflicting implementations of trait `Foo`
```
### Breakage due to removal of incomplete candidate preference
Fixes#107887. In the old solver we incompletely prefer the builtin trait object impl over user defined impls. This can break inference guidance, inferring `?x` in `dyn Trait<u32>: Trait<?x>` to `u32`, even if an explicit impl of `Trait<u64>` also exists.
This caused coherence to incorrectly allow overlapping impls, resulting in ICEs and a theoretical unsoundness. See https://github.com/rust-lang/rust/issues/107887#issuecomment-1997261676. This compiles on stable but results in an overlap error with `-Znext-solver=coherence`:
```rust
// revisions: current next
//[next] compile-flags: -Znext-solver=coherence
struct W<T: ?Sized>(*const T);
trait Trait<T: ?Sized> {
type Assoc;
}
// This would trigger the check for overlap between automatic and custom impl.
// They actually don't overlap so an impl like this should remain possible
// forever.
//
// impl Trait<u64> for dyn Trait<u32> {}
trait Indirect {}
impl Indirect for dyn Trait<u32, Assoc = ()> {}
impl<T: Indirect + ?Sized> Trait<u64> for T {
type Assoc = ();
}
// Incomplete impl where `dyn Trait<u32>: Trait<_>` does not hold, but
// `dyn Trait<u32>: Trait<u64>` does.
trait EvaluateHack<U: ?Sized> {}
impl<T: ?Sized, U: ?Sized> EvaluateHack<W<U>> for T
where
T: Trait<U, Assoc = ()>, // incompletely constrains `_` to `u32`
U: IsU64,
T: Trait<U, Assoc = ()>, // incompletely constrains `_` to `u32`
{
}
trait IsU64 {}
impl IsU64 for u64 {}
trait Overlap<U: ?Sized> {
type Assoc: Default;
}
impl<T: ?Sized + EvaluateHack<W<U>>, U: ?Sized> Overlap<U> for T {
type Assoc = Box<u32>;
}
impl<U: ?Sized> Overlap<U> for dyn Trait<u32, Assoc = ()> {
//[next]~^ ERROR conflicting implementations of trait `Overlap<_>`
type Assoc = usize;
}
```
### Considering region outlives bounds in the `leak_check`
For details on the `leak_check`, see the FCP proposal in #119820.[^leak_check]
[^leak_check]: which should get moved to the dev-guide once that PR lands :3
In both coherence and during candidate selection, the `leak_check` relies on the region constraints added in `evaluate`. It therefore currently does not register outlives obligations: [source](ccb1415eac/compiler/rustc_trait_selection/src/traits/select/mod.rs (L792-L810)). This was likely done as a performance optimization without considering its impact on the `leak_check`. This is the case as in the old solver, *evaluatation* and *fulfillment* are split, with evaluation being responsible for candidate selection and fulfillment actually registering all the constraints.
This split does not exist with the new solver. The `leak_check` can therefore eagerly detect errors caused by region outlives obligations. This improves both coherence itself and candidate selection:
```rust
// revisions: current next
//[next] compile-flags: -Znext-solver=coherence
trait LeakErr<'a, 'b> {}
// Using this impl adds an `'b: 'a` bound which results
// in a higher-ranked region error. This bound has been
// previously ignored but is now considered.
impl<'a, 'b: 'a> LeakErr<'a, 'b> for () {}
trait NoOverlapDir<'a> {}
impl<'a, T: for<'b> LeakErr<'a, 'b>> NoOverlapDir<'a> for T {}
impl<'a> NoOverlapDir<'a> for () {}
//[current]~^ ERROR conflicting implementations of trait `NoOverlapDir<'_>`
// --------------------------------------
// necessary to avoid coherence unknowable candidates
struct W<T>(T);
trait GuidesSelection<'a, U> {}
impl<'a, T: for<'b> LeakErr<'a, 'b>> GuidesSelection<'a, W<u32>> for T {}
impl<'a, T> GuidesSelection<'a, W<u8>> for T {}
trait NotImplementedByU8 {}
trait NoOverlapInd<'a, U> {}
impl<'a, T: GuidesSelection<'a, W<U>>, U> NoOverlapInd<'a, U> for T {}
impl<'a, U: NotImplementedByU8> NoOverlapInd<'a, U> for () {}
//[current]~^ conflicting implementations of trait `NoOverlapInd<'_, _>`
```
### Removal of `fn match_fresh_trait_refs`
The old solver tries to [eagerly detect unbounded recursion](b14fd2359f/compiler/rustc_trait_selection/src/traits/select/mod.rs (L1196-L1211)), forcing the affected goals to be ambiguous. This check is only an approximation and has not been added to the new solver.
The check is not necessary in the new solver and it would be problematic for caching. As it depends on all goals currently on the stack, using a global cache entry would have to always make sure that doing so does not circumvent this check.
This changes some goals to error - or succeed - instead of failing with ambiguity. This allows more code to compile:
```rust
// revisions: current next
//[next] compile-flags: -Znext-solver=coherence
// Need to use this local wrapper for the impls to be fully
// knowable as unknowable candidate result in ambiguity.
struct Local<T>(T);
trait Trait<U> {}
// This impl does not hold, but is ambiguous in the old
// solver due to its overflow approximation.
impl<U> Trait<U> for Local<u32> where Local<u16>: Trait<U> {}
// This impl holds.
impl Trait<Local<()>> for Local<u8> {}
// In the old solver, `Local<?t>: Trait<Local<?u>>` is ambiguous,
// resulting in `Local<?u>: NoImpl`, also being ambiguous.
//
// In the new solver the first impl does not apply, constraining
// `?u` to `Local<()>`, causing `Local<()>: NoImpl` to error.
trait Indirect<T> {}
impl<T, U> Indirect<U> for T
where
T: Trait<U>,
U: NoImpl
{}
// Not implemented for `Local<()>`
trait NoImpl {}
impl NoImpl for Local<u8> {}
impl NoImpl for Local<u16> {}
// `Local<?t>: Indirect<Local<?u>>` cannot hold, so
// these impls do not overlap.
trait NoOverlap<U> {}
impl<T: Indirect<U>, U> NoOverlap<U> for T {}
impl<T, U> NoOverlap<Local<U>> for Local<T> {}
//~^ ERROR conflicting implementations of trait `NoOverlap<Local<_>>`
```
### Non-fatal overflow
The old solver immediately emits a fatal error when hitting the recursion limit. The new solver instead returns overflow. This both allows more code to compile and is results in performance and potential future compatability issues.
Non-fatal overflow is generally desirable. With fatal overflow, changing the order in which we evaluate nested goals easily causes breakage if we have goal which errors and one which overflows. It is also required to prevent breakage due to the removal of `fn match_fresh_trait_refs`, e.g. [in `typenum`](https://github.com/rust-lang/trait-system-refactor-initiative/issues/73).
#### Enabling more code to compile
In the below example, the old solver first tried to prove an overflowing goal, resulting in a fatal error. The new solver instead returns ambiguity due to overflow for that goal, causing the implicit negative overlap check to succeed as `Box<u32>: NotImplemented` does not hold.
```rust
// revisions: current next
//[next] compile-flags: -Znext-solver=coherence
//[current] ERROR overflow evaluating the requirement
trait Indirect<T> {}
impl<T: Overflow<()>> Indirect<T> for () {}
trait Overflow<U> {}
impl<T, U> Overflow<U> for Box<T>
where
U: Indirect<Box<Box<T>>>,
{}
trait NotImplemented {}
trait Trait<U> {}
impl<T, U> Trait<U> for T
where
// T: NotImplemented, // causes old solver to succeed
U: Indirect<T>,
T: NotImplemented,
{}
impl Trait<()> for Box<u32> {}
```
#### Avoiding hangs with non-fatal overflow
Simply returning ambiguity when reaching the recursion limit can very easily result in hangs, e.g.
```rust
trait Recur {}
impl<T, U> Recur for ((T, U), (U, T))
where
(T, U): Recur,
(U, T): Recur,
{}
trait NotImplemented {}
impl<T: NotImplemented> Recur for T {}
```
This can happen quite frequently as it's easy to have exponential blowup due to multiple nested goals at each step. As the trait solver is depth-first, this immediately caused a fatal overflow error in the old solver. In the new solver we have to handle the whole proof tree instead, which can very easily hang.
To avoid this we restrict the recursion depth after hitting the recursion limit for the first time. We also **ignore all inference constraints from goals resulting in overflow**. This is mostly backwards compatible as any overflow in the old solver resulted in a fatal error.
### sidenote about normalization
We return ambiguous nested goals of `NormalizesTo` goals to the caller and ignore their impact when computing the `Certainty` of the current goal. See the [normalization chapter](https://rustc-dev-guide.rust-lang.org/solve/normalization.html) for more details.This means we apply constraints resulting from other nested goals and from equating the impl header when normalizing, even if a nested goal results in overflow. This is necessary to avoid breaking the following example:
```rust
trait Trait {
type Assoc;
}
struct W<T: ?Sized>(*mut T);
impl<T: ?Sized> Trait for W<W<T>>
where
W<T>: Trait,
{
type Assoc = ();
}
// `W<?t>: Trait<Assoc = u32>` does not hold as
// `Assoc` gets normalized to `()`. However, proving
// the where-bounds of the impl results in overflow.
//
// For this to continue to compile we must not discard
// constraints from normalizing associated types.
trait NoOverlap {}
impl<T: Trait<Assoc = u32>> NoOverlap for T {}
impl<T: ?Sized> NoOverlap for W<T> {}
```
#### Future compatability concerns
Non-fatal overflow results in some unfortunate future compatability concerns. Changing the approach to avoid more hangs by more strongly penalizing overflow can cause breakage as we either drop constraints or ignore candidates necessary to successfully compile. Weakening the overflow penalities instead allows more code to compile and strengthens inference while potentially causing more code to hang.
While the current approach is not perfect, we believe it to be good enough. We believe it to apply the necessary inference constraints to avoid breakage and expect there to not be any desirable patterns broken by our current penalities. Similarly we believe the current constraints to avoid most accidental hangs. Ignoring constraints of overflowing goals is especially useful, as it may allow major future optimizations to our overflow handling. See [this summary](https://hackmd.io/ATf4hN0NRY-w2LIVgeFsVg) and the linked documents in case you want to know more.
### changes to performance
In general, trait solving during coherence checking is not significant for performance. Enabling the next-generation trait solver in coherence does not impact our compile time benchmarks. We are still unable to compile the benchmark suite when fully enabling the new trait solver.
There are rare cases where the new solver has significantly worse performance due to non-fatal overflow, its reliance on fixpoint algorithms and the removal of the `fn match_fresh_trait_refs` approximation. We encountered such issues in [`typenum`](https://crates.io/crates/typenum) and believe it should be [pretty much as bad as it can get](https://github.com/rust-lang/trait-system-refactor-initiative/issues/73).
Due to an improved structure and far better caching, we believe that there is a lot of room for improvement and that the new solver will outperform the existing implementation in nearly all cases, sometimes significantly. We have not yet spent any time micro-optimizing the implementation and have many unimplemented major improvements, such as fast-paths for trivial goals.
TODO: get some rough results here and put them in a table
### Unstable features
#### Unsupported unstable features
The new solver currently does not support all unstable features, most notably `#![feature(generic_const_exprs)]`, `#![feature(associated_const_equality)]` and `#![feature(adt_const_params)]` are not yet fully supported in the new solver. We are confident that supporting them is possible, but did not consider this to be a priority. This stabilization introduces new ICE when using these features in impl headers.
#### fixes to `#![feature(specialization)]`
- fixes#105782
- fixes#118987
#### fixes to `#![feature(type_alias_impl_trait)]`
- fixes#119272
- https://github.com/rust-lang/rust/issues/105787#issuecomment-1750112388
- fixes#124207
## This does not stabilize the whole solver
While this stabilizes the use of the new solver in coherence checking, there are many parts of the solver which will remain fully unstable. We may still adapt these areas while working towards stabilizing the new solver everywhere. We are confident that we are able to do so without negatively impacting coherence.
### goals with a non-empty `ParamEnv`
Coherence always uses an empty environment. We therefore do not depend on the behavior of `AliasBound` and `ParamEnv` candidates. We only stabilizes the behavior of user-defined and builtin implementations of traits. There are still many open questions there.
### opaque types in the defining scope
The handling of opaque types - `impl Trait` - in both the new and old solver is still not fully figured out. Luckily this can be ignored for now. While opaque types are reachable during coherence checking by using `impl_trait_in_associated_types`, the behavior during coherence is separate and self-contained. The old and new solver fully agree here.
### normalization is hard
This stabilizes that we equate associated types involving bound variables using deferred-alias-equality. We also stop eagerly normalizing in coherence, which should not have any user-facing impact.
We do not stabilize the normalization behavior outside of coherence, e.g. we currently deeply normalize all types during writeback with the new solver. This may change going forward
### how to replace `select` from the old solver
We sometimes depend on getting a single `impl` for a given trait bound, e.g. when resolving a concrete method for codegen/CTFE. We do not depend on this during coherence, so the exact approach here can still be freely changed going forward.
## Acknowledgements
This work would not have been possible without `@compiler-errors.` He implemented large chunks of the solver himself but also and did a lot of testing and experimentation, eagerly discovering multiple issues which had a significant impact on our approach. `@BoxyUwU` has also done some amazing work on the solver. Thank you for the endless hours of discussion resulting in the current approach. Especially the way aliases are handled has gone through multiple revisions to get to its current state.
There were also many contributions from - and discussions with - other members of the community and the rest of `@rust-lang/types.` This solver builds upon previous improvements to the compiler, as well as lessons learned from `chalk` and `a-mir-formality`. Getting to this point would not have been possible without that and I am incredibly thankful to everyone involved. See the [list of relevant PRs](https://github.com/rust-lang/rust/pulls?q=is%3Apr+is%3Amerged+label%3AWG-trait-system-refactor+-label%3Arollup+closed%3A%3C2024-03-22+).
Autodiff Upstreaming - enzyme backend
Tracking issue: https://github.com/rust-lang/rust/issues/124509
Part of https://github.com/rust-lang/rust/pull/129175
This PR should allow building Enzyme from source on Tier 1 targets (when also building LLVM), except MSVC.
It's only a small fraction (~200 lines) of the whole upstream PR, but due to bootstrapping and the number of configurations in which rustc can be build I assume that this will be the hardest to merge, so I'm starting with it.
Happy to hear what changes are required to be able to upstream this code.
**Content:**
It contains a new configure flag `--enable-llvm-enzyme`, and will build the new Enzyme submodule when it is set.
**Discussion:**
Apparently Rust CI isn't able to clone repositories outside the rust-lang org? At least I'm seeing this error in CI:
```
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
```
Does that mean we would need to mirror github.com/EnzymeAD/Enzyme in rust-lang, until LLVM upgrades Enzyme from an Incubator project to something that ships as part of the monorepo?
Tracking:
- https://github.com/rust-lang/rust/issues/124509
forward linker option to lint-docs
This fixes an error found when building the doc for a cross-built toolchain.
```
warning: the code example in lint `unstable_syntax_pre_expansion` in /buildroots/chenx97/rustc-1.80.1-src/compiler/rustc_lint_defs/src/builtin.rs failed to generate the expected output: did not find lint `unstable_syntax_p
re_expansion` in output of example, got:
error: linking with `cc` failed: exit status: 1
...
```
Closes: #129956
copy rustc rustlib artifacts from ci-rustc
We recently (since https://github.com/rust-lang/rust/pull/129311) had an issue because some rustlib files were missing (like: "error[E0463]: can't find crate for rustc_ast") when building tools that rely on rustc. This patch fixes that by copying those files as required.
r? Kobzol
Blocker for https://github.com/rust-lang/rust/pull/122709
explain why Rvalue::Len still exists
I just spent a bit of time trying to remove this until I realized why that's non-trivial. Let's document that for the next person. :)
bootstrap: Try to track down why `initial_libdir` sometimes fails
When I try to run `x` commands from the command-line, I occasionally see a mysterious failure that looks something like this:
```text
thread 'main' panicked at src/lib.rs:341:14:
called `Result::unwrap()` on an `Err` value: StripPrefixError(())
```
It happens often enough to be annoying, but rarely enough that I can't reproduce it at will. The error message points to a particular `unwrap` call, but doesn't include enough context to determine *why* the failure occurs.
Re-running the command almost always works, so I suspect some kind of filesystem race condition (possibly involving VSCode invoking bootstrap at the same time), but there's not much I can do with the information I currently have.
So this PR includes some relevant information in the panic message when the failure occurs, in the hope that doing so will make the cause easier to track down when the failure occurs again.
fix ICE when `asm_const` and `const_refs_to_static` are combined
fixes https://github.com/rust-lang/rust/issues/129462fixes#126896fixes#124164
I think this is a case that was missed in the fix for https://github.com/rust-lang/rust/pull/125558, which inserts a type error in the case of an invalid (that is, non-integer) type being passed to an asm `const` operand.
I'm not 100% sure that `span_mirbug_and_err` is the right macro here, but it is used earlier with `builtin_deref` and seems to do the trick.
r? ``@lcnr``
Add an internal lint that warns when accessing untracked data
Some methods access data that is not tracked by the query system and should be used with caution. As suggested in https://github.com/rust-lang/rust/pull/128815#issuecomment-2275488683, in this PR I propose a lint (modeled on the `potential_query_instability` lint) that warns when using some specially-annotatted functions.
I can't tell myself if this lint would be that useful, compared to renaming `Steal::is_stolen` to `is_stolen_untracked`. This would depend on whether there are other functions we'd want to lint like this. So far it seems they're called `*_untracked`, which may be clear enough.
r? ``@oli-obk``
Update cargo
9 commits in 8f40fc59fb0c8df91c97405785197f3c630304ea..c1fa840a85eca53818895901a53fae34247448b2
2024-08-21 22:37:06 +0000 to 2024-08-29 21:03:53 +0000
- fix(resolve): With `latest` message, differentiate actionable updates (rust-lang/cargo#14461)
- fix(pkgid): Allow open namespaces in PackageIdSpec's (rust-lang/cargo#14467)
- feat(resolve): Report incompatible-with-rustc when MSRV-resolver is disabled (rust-lang/cargo#14459)
- fix(resolve): Report incompatible packages with precise Rust version (rust-lang/cargo#14457)
- fix(resolve): Dont show locking workspace members (rust-lang/cargo#14445)
- Log details of failure if no errors were seen (rust-lang/cargo#14453)
- More helpful missing feature error message (rust-lang/cargo#14436)
- feat: Add matches_prerelease semantic (rust-lang/cargo#14305)
- refactor(update): Prepare for smarter update messages (rust-lang/cargo#14440)
r? ghost
Apply size optimizations to panic machinery and some cold functions
* std dependencies gimli and addr2line are now built with opt-level=s
* various panic-related methods and `#[cold]` methods are now marked `#[optimize(size)]`
Panics should be cold enough that it doesn't make sense to optimize them for speed. The only tradeoff here is if someone does a lot of backtrace captures (without panics) and printing then the opt-level change might impact their perf.
Seems to be the first use of the optimize attribute. Tracking issue #54882
Rewrite lint_expectations in a single pass.
This PR aims at reducing the perf regression from https://github.com/rust-lang/rust/pull/120924#issuecomment-2202486203 with drive-by simplifications.
Basically, instead of using the lint level builder, which is slow, this PR splits `lint_expectations` logic in 2:
- listing the `LintExpectations` is done in `shallow_lint_levels_on`, on a per-owner basis;
- building the unstable->stable expectation id map is done by iterating on attributes.
r? ghost for perf
add `aarch64_unknown_nto_qnx700` target - QNX 7.0 support for aarch64le
This backports the QNX 7.1 aarch64 implementation to 7.0.
* [x] required `-lregex` disabled, see https://github.com/rust-lang/libc/pull/3775 (released in libc 0.2.156)
* [x] uses `libgcc.a` instead of `libgcc_s.so` (7.0 used ancient GCC 5.4 which didn't have gcc_s)
* [x] a fix in `backtrace` crate to support stack traces https://github.com/rust-lang/backtrace-rs/pull/648
This PR bumps libc dependency to 0.2.158
CC: to the folks who did the [initial implementation](https://doc.rust-lang.org/rustc/platform-support/nto-qnx.html): `@flba-eb,` `@gh-tr,` `@jonathanpallant,` `@japaric`
# Compile target
```bash
# Configure qcc build environment
source _path_/_to_/qnx7.0/qnxsdp-env.sh
# Tell rust to use qcc when building QNX 7.0 targets
export build_env='
CC_aarch64-unknown-nto-qnx700=qcc
CFLAGS_aarch64-unknown-nto-qnx700=-Vgcc_ntoaarch64le_cxx
CXX_aarch64-unknown-nto-qnx700=qcc
AR_aarch64_unknown_nto_qnx700=ntoaarch64-ar'
# Build rust compiler, libs, and the remote test server
env $build_env ./x.py build \
--target x86_64-unknown-linux-gnu,aarch64-unknown-nto-qnx700 \
rustc library/core library/alloc library/std src/tools/remote-test-server
rustup toolchain link stage1 build/host/stage1
```
# Compile "hello world"
```bash
source _path_/_to_/qnx7.0/qnxsdp-env.sh
cargo new hello_world
cd hello_world
cargo +stage1 build --release --target aarch64-unknown-nto-qnx700
```
# Configure a remote for testing
Do this from a new shell - we will need to run more commands in the previous one. I ran into these two issues, and found some workarounds.
* Temporary dir might not work properly
* Default `remote-test-server` has issues binding to an address
```
# ./remote-test-server
starting test server
thread 'main' panicked at src/tools/remote-test-server/src/main.rs:175:29:
called `Result::unwrap()` on an `Err` value: Os { code: 249, kind: AddrNotAvailable, message: "Can't assign requested address" }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```
Specifying `--bind` param actually fixes that, and so does setting `TMPDIR` properly.
```bash
# Copy remote-test-server to remote device. You may need to use sftp instead.
# ATTENTION: Note that the path is different from the one in the remote testing documentation for some reason
scp ./build/x86_64-unknown-linux-gnu/stage1-tools-bin/remote-test-server qnxdevice:/path/
# Run ssh with port forwarding - so that rust tester can connect to the local port instead
ssh -L 12345:127.0.0.1:12345 qnxdevice
# on the device, run
rm -rf tmp && mkdir -p tmp && TMPDIR=$PWD/tmp ./remote-test-server --bind 0.0.0.0:12345
```
# Run test suit
Assume all previous environment variables are still set, or re-init them
```bash
export TEST_DEVICE_ADDR="localhost:12345"
# tidy needs to be skipped due to using un-published libc dependency
export exclude_tests='
--exclude src/bootstrap
--exclude src/tools/error_index_generator
--exclude src/tools/linkchecker
--exclude src/tools/tidy
--exclude tests/ui-fulldeps
--exclude rustc
--exclude rustdoc
--exclude tests/run-make-fulldeps'
env $build_env ./x.py test $exclude_tests --stage 1 --target aarch64-unknown-nto-qnx700
```
try-job: dist-x86_64-msvc
Rollup of 8 pull requests
Successful merges:
- #128495 (core: use `compare_bytes` for more slice element types)
- #128641 (refactor: standardize duplicate processes in parser)
- #129207 (Lint that warns when an elided lifetime ends up being a named lifetime)
- #129493 (Create opaque definitions in resolver.)
- #129619 (Update stacker to 0.1.17)
- #129672 (Make option-like-enum.rs UB-free and portable)
- #129780 (add crashtests for several old unfixed ICEs)
- #129832 (Remove stray dot in `std::char::from_u32_unchecked` documentation)
r? `@ghost`
`@rustbot` modify labels: rollup
add crashtests for several old unfixed ICEs
Adds several new crashtests for some older ICEs that did not yet have any.
Tests were added for #128097, #119095, #117460 and #126443.
Update stacker to 0.1.17
The main new feature is support for detecting the current stack size on illumos. (See [my blog post] for the context which led to this.)
[my blog post]: https://sunshowers.io/posts/rustc-segfault-illumos/
try-job: x86_64-mingw
refactor: standardize duplicate processes in parser
## Summary
This PR refactors the `read_number` function to standardize duplicate code, improve readability, and enhance efficiency.
## Changes
- Merged the logic for both `max_digits` cases into a single `read_atomically` closure
- Simplified control flow and reduced code duplication
core: use `compare_bytes` for more slice element types
`bool`, `NonZero<u8>`, `Option<NonZero<u8>>` and `ascii::Char` can be compared the same way as `u8`.
Rollup of 11 pull requests
Successful merges:
- #128523 (Add release notes for 1.81.0)
- #129605 (Add missing `needs-llvm-components` directives for run-make tests that need target-specific codegen)
- #129650 (Clean up `library/profiler_builtins/build.rs`)
- #129651 (skip stage 0 target check if `BOOTSTRAP_SKIP_TARGET_SANITY` is set)
- #129684 (Enable Miri to pass pointers through FFI)
- #129762 (Update the `wasm-component-ld` binary dependency)
- #129782 (couple more crash tests)
- #129816 (tidy: say which feature gate has a stability issue mismatch)
- #129818 (make the const-unstable-in-stable error more clear)
- #129824 (Fix code examples buttons not appearing on click on mobile)
- #129826 (library: Fix typo in `core::mem`)
r? `@ghost`
`@rustbot` modify labels: rollup
Remove `#[macro_use] extern crate tracing` from rustdoc and rustfmt
A follow-up to #129767 and earlier PRs doing this for `rustc_*` crates.
r? ```@GuillaumeGomez```
Remove `#[macro_use] extern crate tracing`, round 4
Because explicit importing of macros via use items is nicer (more standard and readable) than implicit importing via #[macro_use]. Continuing the work from #124511, #124914, and #125434. After this PR no `rustc_*` crates use `#[macro_use] extern crate tracing` except for `rustc_codegen_gcc` which is a special case and I will do separately.
r? ```@jieyouxu```
Make the "detect-old-time" UI test more representative
The test code did have an inference failure, but that would have failed
on Rust 1.79 and earlier too. Now it is rewritten to be specifically
affected by 1.80's `impl FromIterator<_> for Box<str>`.
llvm-wrapper: adapt for LLVM API changes
No functional changes intended.
Updates the wrapper for 21eddfac3d.
````@rustbot```` label: +llvm-main
r? ````@nikic````
Consider field attributes when converting from tuple to named struct and the opposite
Fixes#17983.
I tried to use the `SourceChangeBuilder::make_mut()` API, but it duplicated the attribute...
