s390x: Fix a regression related to backchain feature
In #127506, we introduced a new IBM Z-specific target feature, `backchain`.
This particular `target-feature` was available as a function-level attribute in LLVM 17 and below, so some hacks were used to avoid blowing up LLVM when querying the supported LLVM features.
This led to an unfortunate regression where `cfg!(target-feature = "backchain")` will always return true.
This pull request aims to fix this issue, and a test has been introduced to ensure it will never happen again.
Fixes#129927.
r? `@RalfJung`
Add Suggestions for Misspelled Keywords
Fixes#97793
This PR detects misspelled keywords using two heuristics:
1. Lowercasing the unexpected identifier.
2. Using edit distance to find a keyword similar to the unexpected identifier.
However, it does not detect each and every misspelled keyword to
minimize false positives and ambiguities. More details about the
implementation can be found in the comments.
Do not request sanitizers for naked functions
Naked functions can only contain inline asm, so any instrumentation inserted by sanitizers is illegal. Don't request it.
Fixes https://github.com/rust-lang/rust/issues/129224.
This PR detects misspelled keywords using two heuristics:
1. Lowercasing the unexpected identifier.
2. Using edit distance to find a keyword similar to the unexpected identifier.
However, it does not detect each and every misspelled keyword to
minimize false positives and ambiguities. More details about the
implementation can be found in the comments.
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.
Because constants are currently emitted *before* the prologue, leaving the
debug location on the IRBuilder spills onto other instructions in the prologue
and messes up both line numbers as well as the point LLVM chooses to be the
prologue end.
Example LLVM IR (irrelevant IR elided):
Before:
define internal { i64, i64 } @_ZN3tmp3Foo18var_return_opt_try17he02116165b0fc08cE(ptr align 8 %self) !dbg !347 {
start:
%self.dbg.spill = alloca [8 x i8], align 8
%_0 = alloca [16 x i8], align 8
%residual.dbg.spill = alloca [0 x i8], align 1
#dbg_declare(ptr %residual.dbg.spill, !353, !DIExpression(), !357)
store ptr %self, ptr %self.dbg.spill, align 8, !dbg !357
#dbg_declare(ptr %self.dbg.spill, !350, !DIExpression(), !358)
After:
define internal { i64, i64 } @_ZN3tmp3Foo18var_return_opt_try17h00b17d08874ddd90E(ptr align 8 %self) !dbg !347 {
start:
%self.dbg.spill = alloca [8 x i8], align 8
%_0 = alloca [16 x i8], align 8
%residual.dbg.spill = alloca [0 x i8], align 1
#dbg_declare(ptr %residual.dbg.spill, !353, !DIExpression(), !357)
store ptr %self, ptr %self.dbg.spill, align 8
#dbg_declare(ptr %self.dbg.spill, !350, !DIExpression(), !358)
Note in particular how !357 from %residual.dbg.spill's dbg_declare no longer
falls through onto the store to %self.dbg.spill. This fixes argument values
at entry when the constant is a ZST (e.g. <Option as Try>::Residual). This
fixes#130003 (but note that it does *not* fix issues with argument values and
non-ZST constants, which emit their own stores that have debug info on them,
like #128945).
This commit changes the way we treat the stability of attributes in the
`#[diagnostic]` namespace. Instead of relaying on ad-hoc checks to
ensure at call side that a certain attribute is really usable at that
location it centralises the logic to one place. For diagnostic
attributes comming from other crates it just skips serializing
attributes that are not stable and that do not have the corresponding
feature enabled. For attributes from the current crate we can just use
the feature information provided by `TyCtx`.
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+).
coverage: Count await when the Future is immediately ready
Currently `await` is only counted towards coverage if the containing
function is suspended and resumed at least once. This is because it
expands to code which contains a branch on the discriminant of `Poll`.
By treating it like a branching macro (e.g. `assert!`), these
implementation details will be hidden from the coverage results.
I added a test to ensure the fix works in simple cases, but the heuristic of picking only the first await-related covspan might be unreliable. I plan on testing more thoroughly with a real codebase over the next couple of weeks.
closes#98712
Make `Ty::boxed_ty` return an `Option`
Looks like a good place to use Rust's type system.
---
Most of 4ac7bcbaad/compiler/rustc_middle/src/ty/sty.rs (L971-L1963) looks like it could be moved to `TyKind` (then I guess `Ty` should be made to deref to `TyKind`).
Check WF of source type's signature on fn pointer cast
This PR patches the implied bounds holes slightly for #129005, #25860.
Like most implied bounds related unsoundness fixes, this isn't complete w.r.t. higher-ranked function signatures, but I believe it implements a pretty good heuristic for now.
### What does this do?
This PR makes a partial patch for a soundness hole in a `FnDef` -> `FnPtr` "reifying" pointer cast where we were never checking that the signature we are casting *from* is actually well-formed. Because of this, and because `FnDef` doesn't require its signature to be well-formed (just its predicates must hold), we are essentially allowed to "cast away" implied bounds that are assumed within the body of the `FnDef`:
```
fn foo<'a, 'b, T>(_: &'a &'b (), v: &'b T) -> &'a T { v }
fn bad<'short, T>(x: &'short T) -> &'static T {
let f: fn(_, &'short T) -> &'static T = foo;
f(&&(), x)
}
```
In this example, subtyping ends up casting the `_` type (which should be `&'static &'short ()`) to some other type that no longer serves as a "witness" to the lifetime relationship `'short: 'static` which would otherwise be required for this call to be WF. This happens regardless of if `foo`'s lifetimes are early- or late-bound.
This PR implements two checks:
1. We check that the signature of the `FnDef` is well-formed *before* casting it. This ensures that there is at least one point in the MIR where we ensure that the `FnDef`'s implied bounds are actually satisfied by the caller.
2. Implements a special case where if we're casting from a higher-ranked `FnDef` to a non-higher-ranked, we instantiate the binder of the `FnDef` with *infer vars* and ensure that it is a supertype of the target of the cast.
The (2.) is necessary to validate that these pointer casts are valid for higher-ranked `FnDef`. Otherwise, the example above would still pass even if `help`'s `'a` lifetime were late-bound.
### Further work
The WF checks for function calls are scattered all over the MIR. We check the WF of args in call terminators, we check the WF of `FnDef` when we create a `const` operand referencing it, and we check the WF of the return type in #115538, to name a few.
One way to make this a bit cleaner is to simply extend #115538 to always check that the signature is WF for `FnDef` types. I may do this as a follow-up, but I wanted to keep this simple since this leads to some pretty bad NLL diagnostics regressions, and AFAICT this solution is *complete enough*.
### Crater triage
Done here: https://github.com/rust-lang/rust/pull/129021#issuecomment-2297702647
r? lcnr
Currently `await` is only counted towards coverage if the containing
function is suspended and resumed at least once. This is because it
expands to code which contains a branch on the discriminant of `Poll`.
By treating it like a branching macro (e.g. `assert!`), these
implementation details will be hidden from the coverage results.
Don't emit `expect`/`assume` in opt-level=0
LLVM does not make use of expect/assume calls in `opt-level=0`, so we can simplify IR by not emitting them in this case.
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. :)
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``
Rename dump of coroutine by-move-body to be more consistent, fix ICE in dump_mir
First, we add a missing match for `DefKind::SyntheticCoroutineBody` in `dump_mir`. Fixes#129703. The second commit (directly below) serves as a test.
Second, we reorder the `dump_mir` in `coroutine_by_move_body_def_id` to be *after* we adjust the body source, and change the disambiguator so it reads more like any other MIR body. This also serves as a test for the ICE, since we're dumping the MIR of a body with `DefKind::SyntheticCoroutineBody`.
Third, we change the parenting of the synthetic MIR body to have the *coroutine-closure* (i.e. async closure) as its parent, so we don't have long strings of `{closure#0}-{closure#0}-{closure#0}`.
try-job: test-various
`impl_trait_overcaptures`: Don't worry about uncaptured contravariant lifetimes if they outlive a captured lifetime
**NOTE:** Review only the first commit carefully. The second one is just moving stuff around, so you can turn whitespace off for that one.
This PR relaxes the `impl_trait_overcaptures` lint to not fire in cases like:
```rust
struct Ctxt<'tcx>(&'tcx ());
impl<'tcx> Ctxt<'tcx> {
fn compute(&self) -> impl Sized + '_ { }
}
```
Specifically, the lint will not fire if **all** overcaptured regions (i.e. those which will be captured in edition 2024, which are not captured today) **satisfy**:
* The region is contravariant (or bivariant) in the function signature
* The region outlives some other region which is captured by the opaque
### The idea behind this
Why is this OK? My reasoning is that since the region is contravariant in the function signature, we know that it can be shortened arbitrarily at the call site. And specifically, we know it can be shortened to be equal to one of the regions that it outlives -- that's why we need to prove that it outlives some other region that *is* captured.
We could technically relax this further, but there would be (IMO somewhat easy) cases to make this a false negative in real code. For example, if the region is invariant, then we can hit issues like:
```rust
struct Ctxt<'tcx>(&'tcx mut &'tcx mut ());
impl<'tcx> Ctxt<'tcx> {
fn compute(&self) -> impl Sized + use<'_, 'tcx> { }
// We use `use<'_, 'tcx>` to show what happens in edition 2024
}
fn test<'a, 'b>(x: &'a Ctxt<'b>, y: &'a Ctxt<'a>) {
let results = [x.compute(), y.compute()];
//~^ ERROR lifetime may not live long enough
// Since both opaques now capture `'tcx`, this enforces that `'a == 'b`.
}
```
### Is this actually totally fine?
There's one case where users might still hit issues, and it's if we turbofish lifetimes directly:
```rust
struct Ctxt<'tcx>(&'tcx ());
impl<'tcx> Ctxt<'tcx> {
fn compute(&self) -> impl Sized + use<'_, 'tcx> { }
}
fn test<'a, 'b>(x: &'a Ctxt<'b>, y: &'a Ctxt<'a>) {
let results = [Ctxt::<'b>::compute(x), Ctxt::<'a>::compute(y)];
//~^ ERROR lifetime may not live long enough
// Since both opaques now capture `'tcx`, this enforces that `'a == 'b`.
// Note that we don't shorten `'b` to `'a` since we turbofished it.
}
```
### Well... we should still warn?
I kinda don't care about this case, though I guess we could possibly downgrade the lint to something like `IMPL_TRAIT_OVERCAPTURES_STRICT` instead of suppressing it altogether. Thoughts? If we were to do this, then I'd probably also opt to include the invariant case in `IMPL_TRAIT_OVERCAPTURES_STRICT` and move it out of `IMPL_TRAIT_OVERCAPTURES`.
- Merge minimum OS version list into one function (makes it easier to
see the logic in it).
- Parse patch deployment target versions.
- Consistently specify deployment target in LLVM target (previously
omitted on `aarch64-apple-watchos`).
Update docs of `missing_abi` lint
The lint docs still said that function ABIs other than "C" have not been added yet.
`@rustbot` labels: +A-docs +A-lint
Arbitrary self types v2: pointers feature gate.
The main `arbitrary_self_types` feature gate will shortly be reused for a new version of arbitrary self types which we are amending per [this RFC](https://github.com/rust-lang/rfcs/blob/master/text/3519-arbitrary-self-types-v2.md). The main amendments are:
* _do_ support `self` types which can't safely implement `Deref`
* do _not_ support generic `self` types
* do _not_ support raw pointers as `self` types.
This PR relates to the last of those bullet points: this strips pointer support from the current `arbitrary_self_types` feature. We expect this to cause some amount of breakage for crates using this unstable feature to allow raw pointer self types. If that's the case, we want to know about it, and we want crate authors to know of the upcoming changes.
For now, this can be resolved by adding the new
`arbitrary_self_types_pointers` feature to such crates. If we determine that use of raw pointers as self types is common, then we may maintain that as an unstable feature even if we come to stabilize the rest of the `arbitrary_self_types` support in future. If we don't hear that this PR is causing breakage, then perhaps we don't need it at all, even behind an unstable feature gate.
[Tracking issue](https://github.com/rust-lang/rust/issues/44874)
This is [step 4 of the plan outlined here](https://github.com/rust-lang/rust/issues/44874#issuecomment-2122179688)
Add target support for RTEMS Arm
# `armv7-rtems-eabihf`
This PR adds a new target for the RTEMS RTOS. To get things started it focuses on Xilinx/AMD Zynq-based targets, but in theory it should also support other armv7-based board support packages in the future.
Given that RTEMS has support for many POSIX functions it is mostly enabling corresponding unix features for the new target.
I also previously started a PR in libc (https://github.com/rust-lang/libc/pull/3561) to add the needed OS specific C-bindings and was told that a PR in this repo is needed first. I will update the PR to the newest version after approval here.
I will probably also need to change one line in the backtrace repo.
Current status is that I could compile rustc for the new target locally (with the updated libc and backtrace) and could compile binaries, link, and execute a simple "Hello World" RTEMS application for the target hardware.
> A proposed target or target-specific patch that substantially changes code shared with other targets (not just target-specific code) must be reviewed and approved by the appropriate team for that shared code before acceptance.
There should be no breaking changes for existing targets. Main changes are adding corresponding `cfg` switches for the RTEMS OS and adding the C binding in libc.
# Tier 3 target policy
> - A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)
I will do the maintenance (for now) further members of the RTEMS community will most likely join once the first steps have been done.
> - Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.
> - Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.
> - If possible, use only letters, numbers, dashes and underscores for the name. Periods (`.`) are known to cause issues in Cargo.
The proposed triple is `armv7-rtems-eabihf`
> - Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users.
> - The target must not introduce license incompatibilities.
> - Anything added to the Rust repository must be under the standard Rust license (`MIT OR Apache-2.0`).
> - The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the `tidy` tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to be subject to any new license requirements.
> - Compiling, linking, and emitting functional binaries, libraries, or other code for the target (whether hosted on the target itself or cross-compiling from another target) must not depend on proprietary (non-FOSS) libraries. Host tools built for the target itself may depend on the ordinary runtime libraries supplied by the platform and commonly used by other applications built for the target, but those libraries must not be required for code generation for the target; cross-compilation to the target must not require such libraries at all. For instance, `rustc` built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3.
> - "onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are _not_ limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users.
The tools consists of the cross-compiler toolchain (gcc-based). The RTEMS kernel (BSD license) and parts of the driver stack of FreeBSD (BSD license). All tools are FOSS and publicly available here: https://gitlab.rtems.org/rtems
There are also no new features or dependencies introduced to the Rust code.
> - Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions.
N/A to me. I am not a reviewer nor Rust team member.
> - Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (`core` for most targets, `alloc` for targets that can support dynamic memory allocation, `std` for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions.
`core` and `std` compile. Some advanced features of the `std` lib might not work yet. However, the goal of this tier 3 target it to make it easier for other people to build and run test applications to better identify the unsupported features and work towards enabling them.
> - The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running binaries, or running tests (even if they do not pass), the documentation must explain how to run such binaries or tests for the target, using emulation if possible or dedicated hardware if necessary.
Building is described in platform support doc. Running simple unit tests works. Running the test suite of the stdlib is currently not that easy. Trying to work towards that after the this target has been added to the nightly.
> - Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via ````@`)``` to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.
Understood.
> - Backlinks such as those generated by the issue/PR tracker when linking to an issue or PR are not considered a violation of this policy, within reason. However, such messages (even on a separate repository) must not generate notifications to anyone involved with a PR who has not requested such notifications.
Ok
> - Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target.
> - In particular, this may come up when working on closely related targets, such as variations of the same architecture with different features. Avoid introducing unconditional uses of features that another variation of the target may not have; use conditional compilation or runtime detection, as appropriate, to let each target run code supported by that target.
I think, I didn't add any breaking changes for any existing targets (see the comment regarding features above).
> - Tier 3 targets must be able to produce assembly using at least one of rustc's supported backends from any host target.
Can produce assembly code via the llvm backend (tested on Linux).
>
> If a tier 3 target stops meeting these requirements, or the target maintainers no longer have interest or time, or the target shows no signs of activity and has not built for some time, or removing the target would improve the quality of the Rust codebase, we may post a PR to remove it; any such PR will be CCed to the target maintainers (and potentially other people who have previously worked on the target), to check potential interest in improving the situation.GIAt this tier, the Rust project provides no official support for a target, so we place minimal requirements on the introduction of targets.
Understood.
r? compiler-team
enable -Zrandomize-layout in debug CI builds
This builds rustc/libs/tools with `-Zrandomize-layout` on *-debug CI runners.
Only a handful of tests and asserts break with that enabled, which is promising. One test was fixable, the rest is dealt with by disabling them through new cargo features or compiletest directives.
The config.toml flag `rust.randomize-layout` defaults to false, so it has to be explicitly enabled for now.
rustc_driver_impl: remove some old dead logic
This got added in 5013952e4a, before `cfg(target_feature)` was stable. It should not be needed any more ever since `cfg(target_feature)` is stable.
Move `SanityCheck` and `MirPass`
They are currently in `rustc_middle`. This PR moves them to `rustc_mir_transform`, which makes more sense.
r? ``@cjgillot``
do not attempt to prove unknowable goals
In case a goal is unknowable, we previously still checked all other possible ways to prove this goal, even though its final result is already guaranteed to be ambiguous. By ignoring all other candidates in that case we can avoid a lot of unnecessary work, fixing the performance regression in typenum found in #121848.
This is already the behavior in the old solver. This could in theory cause future-compatability issues as considering fewer goals unknowable may end up causing performance regressions/hangs. I am quite confident that this will not be an issue.
r? ``@compiler-errors``
update comment regarding TargetOptions.features
The claim that `-Ctarget-features` cannot disable these features set in the target spec is definitely wrong -- I tried it for `x86_64-pc-windows-gnu`, which enables SSE3 that way. Building with `-Ctarget-feature=-sse3` works fine, and `cfg!(target_feature = "sse3")` is `false` in that build.
There are also some indications that these are actually intended to be overwritten:
3b14526cea/compiler/rustc_target/src/spec/targets/i686_unknown_uefi.rs (L22-L23)84ac80f192/compiler/rustc_target/src/spec/targets/x86_64h_apple_darwin.rs (L18-L23)
So... let's update the comment to match reality, I guess?
The claim that they overwrite `-Ctarget-cpu` is based on
- for `native`, the comment in the apple target spec quoted above
- for other CPU strings, the assumption that `LLVMRustCreateTargetMachine` will apply these features after doing whatever the base CPU model does. I am not sure how to check that, I hope some LLVM backend people can chime in. :)
Non-exhaustive structs may be empty
This is a follow-up to a discrepancy noticed in https://github.com/rust-lang/rust/pull/122792: today, the following struct is considered inhabited (non-empty) outside its defining crate:
```rust
#[non_exhaustive]
pub struct UninhabitedStruct {
pub never: !,
// other fields
}
```
`#[non_exhaustive]` on a struct should mean that adding fields to it isn't a breaking change. There is no way that adding fields to this struct could make it non-empty since the `never` field must stay and is inconstructible. I suspect this was implemented this way due to confusion with `#[non_exhaustive]` enums, which indeed should be considered non-empty outside their defining crate.
I propose that we consider such a struct uninhabited (empty), just like it would be without the `#[non_exhaustive]` annotation.
Code that doesn't pass today and will pass after this:
```rust
// In a different crate
fn empty_match_on_empty_struct<T>(x: UninhabitedStruct) -> T {
match x {}
}
```
This is not a breaking change.
r? ``@compiler-errors``
Don't Suggest Labeling `const` and `unsafe` Blocks
Fixes#128604
Previously, both anonymous constant blocks (E.g. The labeled block
inside `['_'; 'block: { break 'block 1 + 2; }]`) and inline const
blocks (E.g. `const { ... }`) were considered to be the same
kind of blocks. This caused the compiler to incorrectly suggest
labeling both the blocks when only anonymous constant blocks can be
labeled.
This PR adds an other enum variant to `Context` so that both the
blocks can be handled appropriately.
Also, adds some doc comments and removes unnecessary `&mut` in a
couple of places.
Suggest `impl Trait` for References to Bare Trait in Function Header
Fixes#125139
This PR suggests `impl Trait` when `&Trait` is found as a function parameter type or return type. This makes use of existing diagnostics by adding `peel_refs()` when checking for type equality.
Additionaly, it makes a few other improvements:
1. Checks if functions inside impl blocks have bare trait in their headers.
2. Introduces a trait `NextLifetimeParamName` similar to the existing `NextTypeParamName` for suggesting a lifetime name. Also, abstracts out the common logic between the two trait impls.
### Related Issues
I ran into a bunch of related diagnostic issues but couldn't fix them within the scope of this PR. So, I have created the following issues:
1. [Misleading Suggestion when Returning a Reference to a Bare Trait from a Function](https://github.com/rust-lang/rust/issues/127689)
2. [Verbose Error When a Function Takes a Bare Trait as Parameter](https://github.com/rust-lang/rust/issues/127690)
3. [Incorrect Suggestion when Returning a Bare Trait from a Function](https://github.com/rust-lang/rust/issues/127691)
r? ```@estebank``` since you implemented #119148
Because that's now the only crate that uses it.
Moving stuff out of `rustc_middle` is always welcome.
I chose to use `impl crate::MirPass`/`impl crate::MirLint` (with
explicit `crate::`) everywhere because that's the only mention of
`MirPass`/`MirLint` used in all of these files. (Prior to this change,
`MirPass` was mostly imported via `use rustc_middle::mir::*` items.)
The actual implementation remains in `rustc_mir_dataflow`, but this
commit moves the `MirPass` impl to `rustc_mir_transform` and changes it
to a `MirLint` (fixing a `FIXME` comment).
(I originally tried moving the full implementation from
`rustc_mir_dataflow` but I had some trait problems with `HasMoveData`
and `RustcPeekAt` and `MaybeLiveLocals`. This commit was much smaller
and simpler, but still will allow some follow-up cleanups.)
Make decoding non-optional `LazyArray` panic if not set
Tables may be [defined](9649706ead/compiler/rustc_metadata/src/rmeta/mod.rs (L377)) as `optional:` or `defaulted:`. If optional, if we try to read a value from a key that was never encoded, we should panic. This has high value in ensuring correctness over a defaulted table, so the tradeoff is worth considering, since it signals the compiler has a buggy encode impl, rather than just defaulting to a value.
HOWEVER, `optional:` arrays were side-stepping this. So this PR fixes that, and makes `optional:` tables of `LazyArray` act like `LazyValue`, and panic if it's not assigned a value during encoding.
During this PR, I found that `deduced_param_attrs` has buggy (?? i think??) implementation where it will refuse to encode cross-crate `deduced_param_attrs` unless we're codegening, we're optimizing the library, and incremental is disabled. This seems incredibly wrong, but I don't want to fix it in this PR.
9649706ead/compiler/rustc_metadata/src/rmeta/encoder.rs (L1733-L1747)
This shrinks `compiler/rustc_codegen_gcc/Cargo.lock` quite a bit. The
only remaining dependencies in `compiler/rustc_codegen_gcc/Cargo.lock`
are `gccjit`, `lang_tester`, and `boml`, all of which aren't used in any
other compiler crates.
The commit also reorders and adds comments to the `extern crate` items
so they match those in miri.
Replace walk with visit so we dont skip outermost expr kind in def collector
This affects async closures with macros as their body expr. Fixes#129855.
r? ``@cjgillot`` or anyone else
Fix LLVM ABI NAME for riscv64imac-unknown-nuttx-elf
This patch fix https://github.com/rust-lang/rust/issues/129825
For the riscv64imac target, the LLVM ABI NAME should be "lp64", which is the default ABI if not specified for the riscv64imac target.
Deny imports of `rustc_type_ir::inherent` outside of type ir + new trait solver
We shouldn't encourage using `rustc_type_ir::inherent` outside of the new solver[^1], though this can happen by accident due to rust-analyzer, for example. See https://github.com/rust-lang/rust/pull/127537#discussion_r1733813842 for an example in practice.
r? fmease
[^1]: Unless we go the fully radical approach of always using these inherent methods everywhere in favor of inherent methods, which would be a major overhaul of the compiler, IMO. I don't really want to consider that possibility right now, tho.
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
This patch fix https://github.com/rust-lang/rust/issues/129825
For the riscv64imac target, the LLVM ABI NAME should be "lp64",
which is the default ABI if not specified for the riscv64imac target.
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
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
make the const-unstable-in-stable error more clear
The default should be to add `rustc_const_unstable`, not `rustc_allow_const_fn_unstable`.
Also I discovered our check for missing const stability attributes on stable functions -- but strangely that check only kicks in for "reachable" functions. `check_missing_stability` checks for reachability since all reachable functions must have a stability attribute, but I would say if a function has `#[stable]` it should also have const-stability attributes regardless of reachability.
Update the `wasm-component-ld` binary dependency
This keeps it up-to-date by moving from 0.5.6 to 0.5.7. While here I've additionally updated some other wasm-related dependencies in the workspace to keep them up-to-date and try to avoid duplicate versions as well.
Enable Miri to pass pointers through FFI
Following https://github.com/rust-lang/rust/pull/126787, the purpose of this PR is to now enable Miri to execute native calls that make use of pointers.
> <details>
>
> <summary> Simple example </summary>
>
> ```rust
> extern "C" {
> fn ptr_printer(ptr: *mut i32);
> }
>
> fn main() {
> let ptr = &mut 42 as *mut i32;
> unsafe {
> ptr_printer(ptr);
> }
> }
> ```
> ```c
> void ptr_printer(int *ptr) {
> printf("printing pointer dereference from C: %d\n", *ptr);
> }
> ```
> should now show `printing pointer dereference from C: 42`.
>
> </details>
Note that this PR does not yet implement any logic involved in updating Miri's "analysis" state (byte initialization, provenance) upon such a native call.
r? ``@RalfJung``
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```
llvm-wrapper: adapt for LLVM API changes
No functional changes intended.
Updates the wrapper for 21eddfac3d.
````@rustbot```` label: +llvm-main
r? ````@nikic````
Expand NLL MIR dumps
This PR is a first step to clean up and expand NLL MIR dumps:
- by restoring the "mir-include-spans" comments which are useful for `-Zdump-mir=nll`
- by adding the list of borrows to NLL MIR dumps, where they are introduced in the CFG and in which region
Comments in MIR dumps were turned off in #112346, but as shown in #114652 they were still useful for us working with NLL MIR dumps. So this PR pulls `-Z mir-include-spans` into its own options struct, so that passes dumping MIR can override them if need be. The rest of the compiler is not affected, only the "nll" pass dumps have these comments enabled again. The CLI still has priority when specifying the flag, so that we can explicitly turn them off in the `mir-opt` tests to keep blessed dumps easier to work with (which was one of the points of #112346).
Then, as part of a couple steps to improve NLL/polonius MIR dumps and `.dot` visualizations, I've also added the list of borrows and where they're introduced. I'm doing all this to help debug some polonius scope issues in my prototype location-sensitive analysis :3. I'll probably add member constraints soon.
const fn stability checking: also check declared language features
Fixes https://github.com/rust-lang/rust/issues/129656
`@oli-obk` I assume it is just an oversight that this didn't use `features().declared()`? Or is there a deep reason that this must only check `declared_lib_features`?
interpret/visitor: make memory order iteration slightly more efficient
Finally I know enough about RPIT to write this iterator signature correctly. :D
This means memory-order iteration now needs an allocation, but it avoids quadratic complexity (where it has to do a linear scan n times to find the n-th field in memory order), so that seems like a win overall. The changed code only affects Miri; the rustc changes are NOPs.
Stop using `ty::GenericPredicates` for non-predicates_of queries
`GenericPredicates` is a struct of several parts: A list of of an item's own predicates, and a parent def id (and some effects related stuff, but ignore that since it's kinda irrelevant). When instantiating these generic predicates, it calls `predicates_of` on the parent and instantiates its predicates, and appends the item's own instantiated predicates too:
acb4e8b625/compiler/rustc_middle/src/ty/generics.rs (L407-L413)
Notice how this should result in a recursive set of calls to `predicates_of`... However, `GenericPredicates` is *also* misused by a bunch of *other* queries as a convenient way of passing around a list of predicates. For these queries, we don't ever set the parent def id of the `GenericPredicates`, but if we did, then this would be very easy to mistakenly call `predicates_of` instead of some other intended parent query.
Given that footgun, and the fact that we don't ever even *use* the parent def id in the `GenericPredicates` returned from queries like `explicit_super_predicates_of`, It really has no benefit over just returning `&'tcx [(Clause<'tcx>, Span)]`.
This PR additionally opts to wrap the results of `EarlyBinder`, as we've tended to use that in the return type of these kinds of queries to properly convey that the user has params to deal with, and it also gives a convenient way of iterating over a slice of things after instantiating.
Remove `Option<!>` return types.
Several compiler functions have `Option<!>` for their return type. That's odd. The only valid return value is `None`, so why is this type used?
Because it lets you write certain patterns slightly more concisely. E.g. if you have these common patterns:
```
let Some(a) = f() else { return };
let Ok(b) = g() else { return };
```
you can shorten them to these:
```
let a = f()?;
let b = g().ok()?;
```
Huh.
An `Option` return type typically designates success/failure. How should I interpret the type signature of a function that always returns (i.e. doesn't panic), does useful work (modifying `&mut` arguments), and yet only ever fails? This idiom subverts the type system for a cute syntactic trick.
Furthermore, returning `Option<!>` from a function F makes things syntactically more convenient within F, but makes things worse at F's callsites. The callsites can themselves use `?` with F but should not, because they will get an unconditional early return, which is almost certainly not desirable. Instead the return value should be ignored. (Note that some of callsites of `process_operand`, `process_immedate`, `process_assign` actually do use `?`, though the early return doesn't matter in these cases because nothing of significance comes after those calls. Ugh.)
When I first saw this pattern I had no idea how to interpret it, and it took me several minutes of close reading to understand everything I've written above. I even started a Zulip thread about it to make sure I understood it properly. "Save a few characters by introducing types so weird that compiler devs have to discuss it on Zulip" feels like a bad trade-off to me. This commit replaces all the `Option<!>` return values and uses `else`/`return` (or something similar) to replace the relevant `?` uses. The result is slightly more verbose but much easier to understand.
r? ``````@cjgillot``````
Simplify some extern providers
Simplifies some extern crate providers:
1. Generalize the `ProcessQueryValue` identity impl to work on non-`Option` types.
2. Allow `ProcessQueryValue` to wrap its output in an `EarlyBinder`, to simplify `explicit_item_bounds`/`explicit_item_super_predicates`.
3. Use `{ table }` and friends more when possible.
Deny `wasm_c_abi` lint to nudge the last 25%
This shouldn't affect projects indirectly depending on wasm-bindgen because cargo passes `--cap-lints=allow` when building dependencies.
The motivation is that the ecosystem has mostly taken up the versions of wasm-bindgen that are compatible in general, but ~25% or so of recent downloads remain on lower versions. However, this change might still be unnecessarily disruptive. I mostly propose it as a discussion point.
linker: Synchronize native library search in rustc and linker
Also search for static libraries with alternative naming (`libname.a`) on MSVC when producing executables or dynamic libraries, and not just rlibs.
This unblocks https://github.com/rust-lang/rust/pull/123436.
try-job: x86_64-msvc
Don't make statement nonterminals match pattern nonterminals
Right now, the heuristic we use to check if a token may begin a pattern nonterminal falls back to `may_be_ident`:
ef71f1047e/compiler/rustc_parse/src/parser/nonterminal.rs (L21-L37)
This has the unfortunate side effect that a `stmt` nonterminal eagerly matches against a `pat` nonterminal, leading to a parse error:
```rust
macro_rules! m {
($pat:pat) => {};
($stmt:stmt) => {};
}
macro_rules! m2 {
($stmt:stmt) => {
m! { $stmt }
};
}
m2! { let x = 1 }
```
This PR fixes it by more accurately reflecting the set of nonterminals that may begin a pattern nonterminal.
As a side-effect, I modified `Token::can_begin_pattern` to work correctly and used that in `Parser::nonterminal_may_begin_with`.
We want to allow setting this on the CLI, override it only in MIR
passes, and disable it altogether in mir-opt tests.
The default value is "only for NLL MIR dumps", which is considered off
for all intents and purposes, except for `rustc_borrowck` when an NLL
MIR dump is requested.
Several compiler functions have `Option<!>` for their return type.
That's odd. The only valid return value is `None`, so why is this type
used?
Because it lets you write certain patterns slightly more concisely. E.g.
if you have these common patterns:
```
let Some(a) = f() else { return };
let Ok(b) = g() else { return };
```
you can shorten them to these:
```
let a = f()?;
let b = g().ok()?;
```
Huh.
An `Option` return type typically designates success/failure. How should
I interpret the type signature of a function that always returns (i.e.
doesn't panic), does useful work (modifying `&mut` arguments), and yet
only ever fails? This idiom subverts the type system for a cute
syntactic trick.
Furthermore, returning `Option<!>` from a function F makes things
syntactically more convenient within F, but makes things worse at F's
callsites. The callsites can themselves use `?` with F but should not,
because they will get an unconditional early return, which is almost
certainly not desirable. Instead the return value should be ignored.
(Note that some of callsites of `process_operand`, `process_immedate`,
`process_assign` actually do use `?`, though the early return doesn't
matter in these cases because nothing of significance comes after those
calls. Ugh.)
When I first saw this pattern I had no idea how to interpret it, and it
took me several minutes of close reading to understand everything I've
written above. I even started a Zulip thread about it to make sure I
understood it properly. "Save a few characters by introducing types so
weird that compiler devs have to discuss it on Zulip" feels like a bad
trade-off to me. This commit replaces all the `Option<!>` return values
and uses `else`/`return` (or something similar) to replace the relevant
`?` uses. The result is slightly more verbose but much easier to
understand.
This keeps it up-to-date by moving from 0.5.6 to 0.5.7. While here I've
additionally updated some other wasm-related dependencies in the
workspace to keep them up-to-date and try to avoid duplicate versions as
well.
Use a reduced recursion limit in the MIR inliner's cycle breaker
This probably papers over https://github.com/rust-lang/rust/issues/128887, but primarily I'm opening this PR because multiple compiler people have thought about making this change which probably means it's a good idea.
r? compiler-errors
debug-fmt-detail option
I'd like to propose a new option that makes `#[derive(Debug)]` generate no-op implementations that don't print anything, and makes `{:?}` in format strings a no-op.
There are a couple of motivations for this:
1. A more thorough stripping of debug symbols. Binaries stripped of debug symbols still retain some of them through `Debug` implementations. It's hard to avoid that without compiler's help, because debug formatting can be used in many places, including dependencies, and their loggers, asserts, panics, etc.
* In my testing it gives about 2% binary size reduction on top of all other binary-minimizing best practices (including `panic_immediate_abort`). There are targets like Web WASM or embedded where users pay attention to binary sizes.
* Users distributing closed-source binaries may not want to "leak" any symbol names as a matter of principle.
2. Adds ability to test whether code depends on specifics of the `Debug` format implementation in unwise ways (e.g. trying to get data unavailable via public interface, or using it as a serialization format). Because current Rust's debug implementation doesn't change, there's a risk of it becoming a fragile de-facto API that [won't be possible to change in the future](https://www.hyrumslaw.com/). An option that "breaks" it can act as a [grease](https://www.rfc-editor.org/rfc/rfc8701.html).
This implementation is a `-Z fmt-debug=opt` flag that takes:
* `full` — the default, current state.
* `none` — makes derived `Debug` and `{:?}` no-ops. Explicit `impl Debug for T` implementations are left unharmed, but `{:?}` format won't use them, so they may get dead-code eliminated if they aren't invoked directly.
* `shallow` — makes derived `Debug` print only the type's name, without recursing into fields. Fieldless enums print their variant names. `{:?}` works.
The `shallow` option is a compromise between minimizing the `Debug` code, and compatibility. There are popular proc-macro crates that use `Debug::fmt` as a way to convert enum values into their Rust source code.
There's a corresponding `cfg` flag: `#[cfg(fmt_debug = "none")]` that can be used in user code to react to this setting to minimize custom `Debug` implementations or remove unnecessary formatting helper functions.
By making it own the index maps, instead of holding references to them.
This requires moving the free function `find_candidate` into
`Candidate::reset_and_find`. It lets the `'alloc` lifetime be removed
everywhere that still has it.
Correct trusty targets to be tier 3
The Trusty targets were added in https://github.com/rust-lang/rust/pull/129490, but in that PR I accidentally marked them as tier 2. This PR corrects the target metadata to mark them as tier 3.
Move `'tcx` lifetime off of impl and onto methods for `CrateMetadataRef`
Unconstrained type and const variables are not allowed, but unconstrained lifetimes are. This is not very good style, though, and it leads to unnecessary captures of a lifetime in edition 2024 (not that it matters, but it does trigger the edition migration lint).
derive(SmartPointer): assume pointee from the single generic and better error messages
Fix#129465
Actually RFC says that `#[pointee]` can be inferred when there is no ambiguity, or there is only one generic type parameter so to say.
cc ```@Darksonn```
r? ```@compiler-errors```
Emit specific message for time<=0.3.35
```
error[E0282]: type annotations needed for `Box<_>`
--> /home/gh-estebank/.cargo/registry/src/index.crates.io-6f17d22bba15001f/time-0.3.34/src/format_description/parse/mod.rs:83:9
|
83 | let items = format_items
| ^^^^^
...
86 | Ok(items.into())
| ---- type must be known at this point
|
= note: this is an inference error on `time` caused by a change in Rust 1.80.0; update `time` to version `>=0.3.36`
```
Partially mitigate the fallout from https://github.com/rust-lang/rust/issues/127343. Although the biggest benefit of this would have been if we had had this in 1.80 before it became stable, the long-tail of that change will be felt for a *long* time, so better late than never.
We can also emit an even more targeted error instead of this inference failure.
Add an ability to convert between `Span` and `visit::Location`
AFAIK, there is no way to create a `Location` from a `Span` because its only field is private. This makes it impossible to use visitor methods like `visit_statement` or `visit_terminator`.
This PR adds an implementation for`From<Span>` for `Location` to fix this.
r? ```@celinval```
rustc_target: Add various aarch64 features
Add various aarch64 features already supported by LLVM and Linux.
Additionally include some comment fixes to ensure consistency of feature names with the Arm ARM.
Compiler support for features added to stdarch by https://github.com/rust-lang/stdarch/pull/1614.
Tracking issue for unstable aarch64 features is https://github.com/rust-lang/rust/issues/127764.
List of added features:
- FEAT_CSSC
- FEAT_ECV
- FEAT_FAMINMAX
- FEAT_FLAGM2
- FEAT_FP8
- FEAT_FP8DOT2
- FEAT_FP8DOT4
- FEAT_FP8FMA
- FEAT_HBC
- FEAT_LSE128
- FEAT_LSE2
- FEAT_LUT
- FEAT_MOPS
- FEAT_LRCPC3
- FEAT_SVE_B16B16
- FEAT_SVE2p1
- FEAT_WFxT
- FEAT_SME
- FEAT_SME_F16F16
- FEAT_SME_F64F64
- FEAT_SME_F8F16
- FEAT_SME_F8F32
- FEAT_SME_FA64
- FEAT_SME_I16I64
- FEAT_SME_LUTv2
- FEAT_SME2
- FEAT_SME2p1
- FEAT_SSVE_FP8DOT2
- FEAT_SSVE_FP8DOT4
- FEAT_SSVE_FP8FMA
FEAT_FPMR is added in the first commit and then removed in a separate one to highlight it being removed from upstream LLVM 19. The intention is for it to be detectable at runtime through stdarch but not have a corresponding Rust compile-time feature.
Implement a first version of RFC 3525: struct target features
This PR is an attempt at implementing https://github.com/rust-lang/rfcs/pull/3525, behind a feature gate `struct_target_features`.
There's obviously a few tasks that ought to be done before this is merged; in no particular order:
- add proper error messages
- add tests
- create a tracking issue for the RFC
- properly serialize/deserialize the new target_features field in `rmeta` (assuming I even understood that correctly :-))
That said, as I am definitely not a `rustc` expert, I'd like to get some early feedback on the overall approach before fixing those things (and perhaps some pointers for `rmeta`...), hence this early PR :-)
Here's an example piece of code that I have been using for testing - with the new code, the calls to intrinsics get correctly inlined:
```rust
#![feature(struct_target_features)]
use std::arch::x86_64::*;
/*
// fails to compile
#[target_feature(enable = "avx")]
struct Invalid(u32);
*/
#[target_feature(enable = "avx")]
struct Avx {}
#[target_feature(enable = "sse")]
struct Sse();
/*
// fails to compile
extern "C" fn bad_fun(_: Avx) {}
*/
/*
// fails to compile
#[inline(always)]
fn inline_fun(_: Avx) {}
*/
trait Simd {
fn do_something(&self);
}
impl Simd for Avx {
fn do_something(&self) {
unsafe {
println!("{:?}", _mm256_setzero_ps());
}
}
}
impl Simd for Sse {
fn do_something(&self) {
unsafe {
println!("{:?}", _mm_setzero_ps());
}
}
}
struct WithAvx {
#[allow(dead_code)]
avx: Avx,
}
impl Simd for WithAvx {
fn do_something(&self) {
unsafe {
println!("{:?}", _mm256_setzero_ps());
}
}
}
#[inline(never)]
fn dosomething<S: Simd>(simd: &S) {
simd.do_something();
}
fn main() {
/*
// fails to compile
Avx {};
*/
if is_x86_feature_detected!("avx") {
let avx = unsafe { Avx {} };
dosomething(&avx);
dosomething(&WithAvx { avx });
}
if is_x86_feature_detected!("sse") {
dosomething(&unsafe { Sse {} })
}
}
```
Tracking:
- https://github.com/rust-lang/rust/issues/129107
```
error[E0282]: type annotations needed for `Box<_>`
--> ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/time-0.3.34/src/format_description/parse/mod.rs:83:9
|
83 | let items = format_items
| ^^^^^
...
86 | Ok(items.into())
| ---- type must be known at this point
|
= note: this is an inference error on crate `time` caused by a change in Rust 1.80.0; update `time` to version `>=0.3.35`
```
Partially address #127343.
coverage: Rename `CodeRegion` to `SourceRegion`
LLVM uses the word "code" to refer to a particular kind of coverage mapping. This unrelated usage of the word is confusing, and makes it harder to introduce types whose names correspond to the LLVM classification of coverage kinds.
No functional changes.
Rename `BikeshedIntrinsicFrom` to `TransmuteFrom`
As our implementation of MCP411 nears completion and we begin to solicit testing, it's no longer reasonable to expect testers to type or remember `BikeshedIntrinsicFrom`. The name degrades the ease-of-reading of documentation, and the overall experience of using compiler safe transmute.
Tentatively, we'll instead adopt `TransmuteFrom`.
This name seems to be the one most likely to be stabilized, after discussion on Zulip [1]. We may want to revisit the ordering of `Src` and `Dst` before stabilization, at which point we'd likely consider `TransmuteInto` or `Transmute`.
[1] https://rust-lang.zulipchat.com/#narrow/stream/216762-project-safe-transmute/topic/What.20should.20.60BikeshedIntrinsicFrom.60.20be.20named.3F
Tracking Issue: https://github.com/rust-lang/rust/issues/99571
r? `@compiler-errors`
interpret: do not make const-eval query result depend on tcx.sess
The check against calling functions with missing target features uses `tcx.sess` to determine which target features are available. However, this can differ between different crates in a crate graph, so the same const-eval query can come to different conclusions about whether a constant evaluates successfully or not -- which is bad, we should consistently get the same result everywhere.
const-eval: do not make UbChecks behavior depend on current crate's flags
Fixes https://github.com/rust-lang/rust/issues/129552
Let's see if we can get away with just always enabling these checks.
add repr to the allowlist for naked functions
Fixes#129412 (combining unstable features #90957 (`#![feature(naked_functions)]`) and #82232 (`#![feature(fn_align)]`)
LLVM uses the word "code" to refer to a particular kind of coverage mapping.
This unrelated usage of the word is confusing, and makes it harder to introduce
types whose names correspond to the LLVM classification of coverage kinds.
Get rid of `predicates_defined_on`
This is the uncontroversial part of #129532. This simply inlines the `predicates_defined_on` into into `predicates_of`. Nothing should change here logically.
Stop storing a special inner body for the coroutine by-move body for async closures
...and instead, just synthesize an item which is treated mostly normally by the MIR pipeline.
This PR does a few things:
* We synthesize a new `DefId` for the by-move body of a closure, which has its `mir_built` fed with the output of the `ByMoveBody` MIR transformation, and some other relevant queries.
* This has the `DefKind::ByMoveBody`, which we use to distinguish it from "real" bodies (that come from HIR) which need to be borrowck'd. Introduce `TyCtxt::is_synthetic_mir` to skip over `mir_borrowck` which is called by `mir_promoted`; borrowck isn't really possible to make work ATM since it heavily relies being called on a body generated from HIR, and is redundant by the construction of the by-move-body.
* Remove the special `PassManager` hacks for handling the inner `by_move_body` stored within the coroutine's mir body. Instead, this body is fed like a regular MIR body, so it's goes through all of the `tcx.*_mir` stages normally (build -> promoted -> ...etc... -> optimized) ✨.
* Remove the `InstanceKind::ByMoveBody` shim, since now we have a "regular" def id, we can just use `InstanceKind::Item`. This also allows us to remove the corresponding hacks from codegen, such as in `fn_sig_for_fn_abi` ✨.
Notable remarks:
* ~~I know it's kind of weird to be using `DefKind::Closure` here, since it's not a distinct closure but just a new MIR body. I don't believe it really matters, but I could also use a different `DefKind`... maybe one that we could use for synthetic MIR bodies in general?~~ edit: We're doing this now.
The main `arbitrary_self_types` feature gate will shortly be reused for
a new version of arbitrary self types which we are amending per [this
RFC](https://github.com/rust-lang/rfcs/blob/master/text/3519-arbitrary-self-types-v2.md).
The main amendments are:
* _do_ support `self` types which can't safely implement `Deref`
* do _not_ support generic `self` types
* do _not_ support raw pointers as `self` types.
This PR relates to the last of those bullet points: this strips pointer
support from the current `arbitrary_self_types` feature.
We expect this to cause some amount of breakage for crates using this
unstable feature to allow raw pointer self types. If that's the case, we
want to know about it, and we want crate authors to know of the upcoming
changes.
For now, this can be resolved by adding the new
`arbitrary_self_types_pointers` feature to such crates. If we determine
that use of raw pointers as self types is common, then we may maintain
that as an unstable feature even if we come to stabilize the rest of the
`arbitrary_self_types` support in future. If we don't hear that this PR
is causing breakage, then perhaps we don't need it at all, even behind
an unstable feature gate.
[Tracking issue](https://github.com/rust-lang/rust/issues/44874)
This is [step 4 of the plan outlined here](https://github.com/rust-lang/rust/issues/44874#issuecomment-2122179688)
make it possible to enable const_precise_live_drops per-function
This makes const_precise_live_drops work with rustc_allow_const_fn_unstable so that we can stabilize individual functions that rely on const_precise_live_drops.
The goal is that we can use that to stabilize some of https://github.com/rust-lang/rust/issues/67441 without having to stabilize const_precise_live_drops.
As our implementation of MCP411 nears completion and we begin to
solicit testing, it's no longer reasonable to expect testers to
type or remember `BikeshedIntrinsicFrom`. The name degrades the
ease-of-reading of documentation, and the overall experience of
using compiler safe transmute.
Tentatively, we'll instead adopt `TransmuteFrom`.
This name seems to be the one most likely to be stabilized, after
discussion on Zulip [1]. We may want to revisit the ordering of
`Src` and `Dst` before stabilization, at which point we'd likely
consider `TransmuteInto` or `Transmute`.
[1] https://rust-lang.zulipchat.com/#narrow/stream/216762-project-safe-transmute/topic/What.20should.20.60BikeshedIntrinsicFrom.60.20be.20named.3F
Convert to_llvm_features to return Option<LLVMFeature> so that it can
return None if the requested feature is not available for the current
LLVM version.
Add match rules to filter out aarch64 features not available in LLVM 17.
FEAT_FPMR has been removed from upstream LLVM as of LLVM 19.
Remove the feature from the target features list and temporarily hack
the LLVM codegen to always enable it until the minimum LLVM version is
bumped to 19.
Add SME aarch64 features already supported by LLVM and Linux.
This commit adds compiler support for the following features:
- FEAT_SME
- FEAT_SME_F16F16
- FEAT_SME_F64F64
- FEAT_SME_F8F16
- FEAT_SME_F8F32
- FEAT_SME_FA64
- FEAT_SME_I16I64
- FEAT_SME_LUTv2
- FEAT_SME2
- FEAT_SME2p1
- FEAT_SSVE_FP8DOT2
- FEAT_SSVE_FP8DOT4
- FEAT_SSVE_FP8FMA
Add various aarch64 features already supported by LLVM and Linux.
The features are marked as unstable using a newly added symbol, i.e.
aarch64_unstable_target_feature.
Additionally include some comment fixes to ensure consistency of
feature names with the Arm ARM and support for architecture version
target features up to v9.5a.
This commit adds compiler support for the following features:
- FEAT_CSSC
- FEAT_ECV
- FEAT_FAMINMAX
- FEAT_FLAGM2
- FEAT_FP8
- FEAT_FP8DOT2
- FEAT_FP8DOT4
- FEAT_FP8FMA
- FEAT_FPMR
- FEAT_HBC
- FEAT_LSE128
- FEAT_LSE2
- FEAT_LUT
- FEAT_MOPS
- FEAT_LRCPC3
- FEAT_SVE_B16B16
- FEAT_SVE2p1
- FEAT_WFxT
Add `f16` and `f128` inline ASM support for `aarch64`
Adds `f16` and `f128` inline ASM support for `aarch64`. SIMD vector types are taken from [the ARM intrinsics list](https://developer.arm.com/architectures/instruction-sets/intrinsics/#f:`@navigationhierarchiesreturnbasetype=[float]&f:@navigationhierarchieselementbitsize=[16]&f:@navigationhierarchiesarchitectures=[A64]).` Based on the work of `@lengrongfu` in #127043.
Relevant issue: #125398
Tracking issue: #116909
`@rustbot` label +F-f16_and_f128
try-job: aarch64-gnu
try-job: aarch64-apple
Add Trusty OS as tier 3 target
This PR adds support for the [Trusty secure operating system](https://source.android.com/docs/security/features/trusty) as a Tier 3 supported target. This upstreams [the patch that we have been using](https://cs.android.com/android/platform/superproject/+/master:external/rust/crates/libc/patches/trusty.patch;l=1;drc=122e586e93a534160230dc10ae3474cf31dd8f7f) internally. This also revives https://github.com/rust-lang/rust/pull/103895 which was closed due to inactivity, and is being resumed now that time allows.
And MCP has already been done for adding this platform: rust-lang/compiler-team/issues/568
# Target Tier Policy Acknowledgements
> A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)
- Nicole LeGare (``@randomPoison)``
- Stephen Crane (``@rinon)``
- As a fallback trusty-dev-team@google.com can be contacted
> Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.
The two new Trusty targets, `aarch64-unknown-trusty` and `armv7-unknown-trusty` both follow the existing naming convention for similar targets.
> Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.
👍
> Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users.
There are no known legal issues or license incompatibilities.
> Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions.
👍
> Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (core for most targets, alloc for targets that can support dynamic memory allocation, std for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions.
This PR only adds the targets for the platform. `std` support will be added once platform support is added to the libc crate, which depends on the language targets being added to rustc.
> The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running binaries, or running tests (even if they do not pass), the documentation must explain how to run such binaries or tests for the target, using emulation if possible or dedicated hardware if necessary.
👍
> Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via ``@)`` to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.
👍
> Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target.
👍
> Tier 3 targets must be able to produce assembly using at least one of rustc's supported backends from any host target. (Having support in a fork of the backend is not sufficient, it must be upstream.)
👍
rustc: Simplify getting sysroot library directory
It was very non-obvious that `sess.target_tlib_path`, `make_target_lib_path(...)`, and `sess.target_filesearch(...).search_paths()` result in the same sysroot library directory paths.
They are however, indeed the same, because `sess.target_tlib_path` is initialized to `make_target_lib_path(...)` on `Session` creation, and they are used interchangeably.
There are still some redundant calls to `make_target_lib_path` and other inconsistent ways to obtain sysroot directories, but fixing that requires some behavior changes, while this PR is a pure refactoring.
Some places in the compiler even disagree on the number of sysroots - 1 (explicit `--sysroot` *or* default sysroot), 2 (explicit `--sysroot` *and* default sysroot), or an unclear number of `sysroot_candidates` every of which is considered.
The logic currently using `sess.target_tlib_path` or equivalents assumes one sysroot.
miri weak memory emulation: put previous value into initial store buffer
Fixes https://github.com/rust-lang/miri/issues/2164 by doing a read before each atomic write so that we can initialize the store buffer. The read suppresses memory access hooks and UB exceptions, to avoid otherwise influencing the program behavior. If the read fails, we store that as `None` in the store buffer, so that when an atomic read races with the first atomic write to some memory and previously the memory was uninitialized, we can report UB due to reading uninit memory.
``@cbeuw`` this changes a bit the way we initialize the store buffers. Not sure if you still remember all this code, but if you could have a look to make sure this still makes sense, that would be great. :)
r? ``@saethlin``
simd_shuffle intrinsic: allow argument to be passed as vector
See https://github.com/rust-lang/rust/issues/128738 for context.
I'd like to get rid of [this hack](6c0b89dfac/compiler/rustc_codegen_ssa/src/mir/block.rs (L922-L935)). https://github.com/rust-lang/rust/pull/128537 almost lets us do that since constant SIMD vectors will then be passed as immediate arguments. However, simd_shuffle for some reason actually takes an *array* as argument, not a vector, so the hack is still required to ensure that the array becomes an immediate (which then later stages of codegen convert into a vector, as that's what LLVM needs).
This PR prepares simd_shuffle to also support a vector as the `idx` argument. Once this lands, stdarch can hopefully be updated to pass `idx` as a vector, and then support for arrays can be removed, which finally lets us get rid of that hack.
Remove `ParamMode::ExplicitNamed`
This was introduced as a hack to improve a diagnostics suggestion in #61679. It was subsequently broken, but also it was an incomplete hack that I don't believe we need to support, so let's just remove it.
Remove Duplicate E0381 Label
Aims to resolve https://github.com/rust-lang/rust/issues/129274, and adds a test for the case.
Essentially, we are duplicating this span for some reason. For now, I'm just using a set to collect the spans rather than the vec. I imagine there's probably no real reason to inspect duplicates in this area, but if I'm wrong I can adjust to collect "seen spans" in just the point where this label is applied.
I'm not sure why it's producing duplicate spans. Looks like this has been this way for a while? I think it gives the duplicate label on 1.75.0 for example.
Do not ICE on non-ADT rcvr type when looking for crate version collision
When looking for multiple versions of the same crate, do not blindly construct the receiver type.
Follow up to #128786.
Fixes#129205Fixes#129216
Document & implement the transmutation modeled by `BikeshedIntrinsicFrom`
Documents that `BikeshedIntrinsicFrom` models transmute-via-union, which is slightly more expressive than the transmute-via-cast implemented by `transmute_copy`. Additionally, we provide an implementation of transmute-via-union as a method on the `BikeshedIntrinsicFrom` trait with additional documentation on the boundary between trait invariants and caller obligations.
Whether or not transmute-via-union is the right kind of transmute to model remains up for discussion [1]. Regardless, it seems wise to document the present behavior.
[1] https://rust-lang.zulipchat.com/#narrow/stream/216762-project-safe-transmute/topic/What.20'kind'.20of.20transmute.20to.20model.3F/near/426331967
Tracking Issue: https://github.com/rust-lang/rust/issues/99571
r? `@compiler-errors`
cc `@scottmcm,` `@Lokathor`
Add `#[warn(unreachable_pub)]` to a bunch of compiler crates
By default `unreachable_pub` identifies things that need not be `pub` and tells you to make them `pub(crate)`. But sometimes those things don't need any kind of visibility. So they way I did these was to remove the visibility entirely for each thing the lint identifies, and then add `pub(crate)` back in everywhere the compiler said it was necessary. (Or occasionally `pub(super)` when context suggested that was appropriate.) Tedious, but results in more `pub` removal.
There are plenty more crates to do but this seems like enough for a first PR.
r? `@compiler-errors`
Tie `impl_trait_overcaptures` lint to Rust 2024
The `impl_trait_overcaptures` lint is part of the migration to Rust 2024 and the Lifetime Capture Rules 2024. Now that we've stabilized precise capturing (RFC 3617), let's tie this lint to the `rust_2024_compatibility` lint group.
Tracking:
- https://github.com/rust-lang/rust/issues/117587
r? `@compiler-errors`
mv `build_reduced_graph_for_external_crate_res` into Resolver
`build_reduced_graph_for_external_crate_res` is only related to `Resolver`, so move it there.
r? `@petrochenkov`
const checking: properly compute the set of transient locals
For const-checking the MIR of a const/static initializer, we have to know the set of "transient" locals. The reason for this is that creating a mutable (or interior mutable) reference to a transient local is "safe" in the sense that this reference cannot possibly end up in the final value of the const -- even if it is turned into a raw pointer and stored in a union, we will see that pointer during interning and reliably reject it as dangling.
So far, we determined the set of transient locals as "locals that have a `StorageDead` somewhere". But that's not quite right -- if we had MIR like
```rust
StorageLive(_5);
StorageDead(_5);
StorageLive(_5);
// no further storage annotations for _5
```
Then we'd consider `_5` to be "transient", but it is not actually transient.
We do not currently generate such MIR, but I feel uneasy relying on subtle invariants like this. So this PR implements a proper analysis for computing the set of "transient" locals: a local is "transient" if it is guaranteed dead at all `Return` terminators.
Cc `@cjgillot`
The `impl_trait_overcaptures` lint is part of the migration to Rust
2024 and the Lifetime Capture Rules 2024. Now that we've stabilized
precise capturing (RFC 3617), let's tie this lint to the
`rust_2024_compatibility` lint group.
add back test for stable-const-can-only-call-stable-const
This got accidentally removed in https://github.com/rust-lang/rust/pull/128596 (file `tests/ui/internal/internal-unstable-const.rs`). The test has little to do with "allow internal unstable" though, so add it in a file that already tests various const stability things.
Also tweak the help that suggests to add `rustc_allow_const_fn_unstable` to make it clear that this needs team approval, since it is a fairly big gun.
Use `FxHasher` on new solver unconditionally
r? lqd
This should actually fix the inference problem in ad855fe6db, since `HashSet::default` was not inferring the hasher when `HashSet` was coming from the stdlib due to the way that defaulted types/inference vars work. You could cherry-pick this on top of your PR alternatively.
rustdoc: clean up tuple <-> primitive conversion docs
This adds a minor missing feature to `fake_variadic`, so that it can render `impl From<(T,)> for [T; 1]` correctly.
Remove redundant flags from `lower_ty_common` that can be inferred from the HIR
...and then get rid of `lower_ty_common`.
r? ``@fmease`` or re-roll if you're busy!
Use subtyping for `UnsafeFnPointer` coercion, too
I overlooked this in #129059, which changed MIR typechecking to use subtyping for other fn pointer coercions.
Fixes#129285
Make `rustc_type_ir` build on stable
This PR fixes a handful of issues that appear in `rustc_type_ir` when trying to build the new solver on stable.
r? ```@compiler-errors```
```@bors``` rollup
library: Move unstable API of new_uninit to new features
- `new_zeroed` variants move to `new_zeroed_alloc`
- the `write` fn moves to `box_uninit_write`
The remainder will be stabilized in upcoming patches, as it was decided to only stabilize `uninit*` and `assume_init`.
Print the generic parameter along with the variance in dumps.
This allows to make sure we are testing what we think we are testing.
While the tests are correct, I discovered that opaque duplicated args are in the reverse declaration order.
Add a special case for `CStr`/`CString` in the `improper_ctypes` lint
Revives #120176. Just needed to bless a test and fix an argument, but seemed reasonable to me otherwise.
Instead of saying to "consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct", we now tell users to "Use `*const ffi::c_char` instead, and pass the value from `CStr::as_ptr()`" when the type involved is a `CStr` or a `CString`.
The suggestion is not made for `&mut CString` or `*mut CString`.
r? ``````@cjgillot`````` (since you were the reviewer of the original PR #120176, but feel free to reroll)
Detect `*` operator on `!Sized` expression
The suggestion is new:
```
error[E0277]: the size for values of type `str` cannot be known at compilation time
--> $DIR/unsized-str-in-return-expr-arg-and-local.rs:15:9
|
LL | let x = *"";
| ^ doesn't have a size known at compile-time
|
= help: the trait `Sized` is not implemented for `str`
= note: all local variables must have a statically known size
= help: unsized locals are gated as an unstable feature
help: references to `!Sized` types like `&str` are `Sized`; consider not dereferencing the expression
|
LL - let x = *"";
LL + let x = "";
|
```
Fix#128199.
Retroactively feature gate `ConstArgKind::Path`
This puts the lowering introduced by #125915 under a feature gate until we fix the regressions introduced by it. Alternative to whole sale reverting the PR since it didn't seem like a very clean revert and I think this is generally a step in the right direction and don't want to get stuck landing and reverting the PR over and over :)
cc #129137 ``@camelid,`` tests taken from there. beta is branching soon so I think it makes sense to not try and rush that fix through since it wont have much time to bake and if it has issues we can't simply revert it on beta.
Fixes#128016
make writes_through_immutable_pointer a hard error
This turns the lint added in https://github.com/rust-lang/rust/pull/118324 into a hard error. This has been reported in cargo's future-compat reports since Rust 1.76 (released in February). Given that const_mut_refs is still unstable, it should be impossible to even hit this error on stable: we did accidentally stabilize some functions that can cause this error, but that got reverted in https://github.com/rust-lang/rust/pull/117905. Still, let's do a crater run just to be sure.
Given that this should only affect unstable code, I don't think it needs an FCP, but let's Cc ``@rust-lang/lang`` anyway -- any objection to making this unambiguous UB into a hard error during const-eval? This can be viewed as part of https://github.com/rust-lang/rust/pull/129195 which is already nominated for discussion.
- `new_zeroed` variants move to `new_zeroed_alloc`
- the `write` fn moves to `box_uninit_write`
The remainder will be stabilized in upcoming patches, as
it was decided to only stabilize `uninit*` and `assume_init`.
By keeping track of attributes that have been previously processed.
This fixes the `macro-rules-derive-cfg.stdout` test, and is necessary
for #124141 which removes nonterminals.
Also shrink the `SmallVec` inline size used in `IntervalSet`. 2 gives
slightly better perf than 4 now that there's an `IntervalSet` in
`Parser`, which is cloned reasonably often.
Documents that `BikeshedIntrinsicFrom` models transmute-via-union,
which is slightly more expressive than the transmute-via-cast
implemented by `transmute_copy`. Additionally, we provide an
implementation of transmute-via-union as a method on the
`BikeshedIntrinsicFrom` trait with additional documentation on
the boundary between trait invariants and caller obligations.
Whether or not transmute-via-union is the right kind of transmute
to model remains up for discussion [1]. Regardless, it seems wise
to document the present behavior.
[1] https://rust-lang.zulipchat.com/#narrow/stream/216762-project-safe-transmute/topic/What.20'kind'.20of.20transmute.20to.20model.3F/near/426331967
Rollup of 9 pull requests
Successful merges:
- #128511 (Document WebAssembly target feature expectations)
- #129243 (do not build `cargo-miri` by default on stable channel)
- #129263 (Add a missing compatibility note in the 1.80.0 release notes)
- #129276 (Stabilize feature `char_indices_offset`)
- #129350 (adapt integer comparison tests for LLVM 20 IR changes)
- #129408 (Fix handling of macro arguments within the `dropping_copy_types` lint)
- #129426 (rustdoc-search: use tighter json for names and parents)
- #129437 (Fix typo in a help diagnostic)
- #129457 (kobzol vacation)
r? `@ghost`
`@rustbot` modify labels: rollup
Fix handling of macro arguments within the `dropping_copy_types` lint
This PR fixes the handling of spans with different context (aka macro arguments) than the primary expression within the different `{drop,forget}ing_copy_types` and `{drop,forget}ing_references` lints.
<details>
<summary>Before</summary>
```
warning: calls to `std::mem::drop` with a value that implements `Copy` does nothing
--> drop_writeln.rs:5:5
|
5 | drop(writeln!(&mut msg, "test"));
| ^^^^^--------------------------^
| |
| argument has type `Result<(), std::fmt::Error>`
|
= note: `#[warn(dropping_copy_types)]` on by default
help: use `let _ = ...` to ignore the expression or result
--> /home/[..]/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/macros/mod.rs:688:9
|
68| let _ =
| ~~~~~~~
```
</details>
<details>
<summary>With this PR</summary>
```
warning: calls to `std::mem::drop` with a value that implements `Copy` does nothing
--> drop_writeln.rs:5:5
|
5 | drop(writeln!(&mut msg, "test"));
| ^^^^^--------------------------^
| |
| argument has type `Result<(), std::fmt::Error>`
|
= note: `#[warn(dropping_copy_types)]` on by default
help: use `let _ = ...` to ignore the expression or result
|
5 - drop(writeln!(&mut msg, "test"));
5 + let _ = writeln!(&mut msg, "test");
|
```
</details>
``````@rustbot`````` label +L-dropping_copy_types
In a case like this:
```
mod a {
mod b {
#[cfg_attr(unix, inline)]
fn f() {
#[cfg_attr(linux, inline)]
fn g1() {}
#[cfg_attr(linux, inline)]
fn g2() {}
}
}
}
```
We currently end up with the following replacement ranges.
- The lazy tokens for `f` has replacement ranges for `g1` and `g2`.
- The lazy tokens for `a` has replacement ranges for `f`, `g1`, and
`g2`.
I.e. the replacement ranges for `g1` and `g2` are duplicated. In
general, replacement ranges for inner AST nodes are duplicated up the
chain for each nested `collect_tokens` call. And the code that processes
the replacements is careful about the ordering in which the replacements
are applied, to ensure that inner replacements are applied before outer
replacements.
But all of this is unnecessary. If you apply an inner replacement and
then an outer replacement, the outer replacement completely overwrites
the inner replacement.
This commit avoids the duplication by removing replacements from
`self.capture_state.parser_replacements` when they are used. (The effect
on the example above is that the lazy tokesn for `a` no longer include
replacement ranges for `g1` and `g2`.) This eliminates the possibility
of nested replacements on individual AST nodes, which avoids the need
for careful ordering of replacements.
This example triggers an assertion failure:
```
fn f() -> u32 {
#[cfg_eval] #[cfg(not(FALSE))] 0
}
```
The sequence of events:
- `configure_annotatable` calls `parse_expr_force_collect`, which calls
`collect_tokens`.
- Within that, we end up in `parse_expr_dot_or_call`, which again calls
`collect_tokens`.
- The return value of the `f` call is the expression `0`.
- This inner call collects tokens for `0` (parser range 10..11) and
creates a replacement covering `#[cfg(not(FALSE))] 0` (parser range
0..11).
- We return to the outer `collect_tokens` call. The return value of the
`f` call is *again* the expression `0`, again with the range 10..11,
but the replacement from earlier covers the range 0..11. The code
mistakenly assumes that any attributes from an inner `collect_tokens`
call fit entirely within the body of the result of an outer
`collect_tokens` call. So it adjusts the replacement parser range
0..11 to a node range by subtracting 10, resulting in -10..1. This is
an invalid range and triggers an assertion failure.
It's tricky to follow, but basically things get complicated when an AST
node is returned from an inner `collect_tokens` call and then returned
again from an outer `collect_token` node without being wrapped in any
kind of additional layer.
This commit changes `collect_tokens` to return early in some extra cases,
avoiding the construction of lazy tokens. In the example above, the
outer `collect_tokens` returns earlier because the `0` token already has
tokens and `self.capture_state.capturing` is `Capturing::No`. This early
return avoids the creation of the invalid range and the assertion
failure.
Fixes#129166. Note: these invalid ranges have been happening for a long
time. #128725 looks like it's at fault only because it introduced the
assertion that catches the invalid ranges.
Allow rust staticlib to work with MSVC's /WHOLEARCHIVE
This fixes#129020 by renaming the `__NULL_IMPORT_DESCRIPTOR` to prevent conflicts.
try-job: dist-i686-msvc
Rollup of 8 pull requests
Successful merges:
- #128432 (WASI: forbid `unsafe_op_in_unsafe_fn` for `std::{os, sys}`)
- #129373 (Add missing module flags for CFI and KCFI sanitizers)
- #129374 (Use `assert_unsafe_precondition!` in `AsciiChar::digit_unchecked`)
- #129376 (Change `assert_unsafe_precondition` docs to refer to `check_language_ub`)
- #129382 (Add `const_cell_into_inner` to `OnceCell`)
- #129387 (Advise against removing the remaining Python scripts from `tests/run-make`)
- #129388 (Do not rely on names to find lifetimes.)
- #129395 (Pretty-print own args of existential projections (dyn-Trait w/ GAT constraints))
r? `@ghost`
`@rustbot` modify labels: rollup
Pretty-print own args of existential projections (dyn-Trait w/ GAT constraints)
Previously we would just drop them. This bug isn't that significant as it can only be triggered by user code that constrains GATs inside trait object types which is currently gated under the interim feature `generic_associated_types_extended` (whose future is questionable) or on stable if the GATs are 'disabled' in dyn-Trait via `where Self: Sized` (in which case the assoc type bindings get ignored anyway (and trigger the warn-by-default lint `unused_associated_type_bounds`)), so yeah.
Affects diagnostic output and output of `std::any::type_name{_of_val}`.
Do not rely on names to find lifetimes.
For some reason, we were trying to find the lifetime parameter from its name, instead of using the def_id we have.
This PR uses it instead. This changes some ui tests, I think to be more sensible.
Add missing module flags for CFI and KCFI sanitizers
Set the cfi-normalize-integers and kcfi-offset module flags when Control-Flow Integrity sanitizers are used, so functions generated by the LLVM backend use the same CFI/KCFI options as rustc.
cfi-normalize-integers tells LLVM to also use integer normalization for generated functions when -Zsanitizer-cfi-normalize-integers is used.
kcfi-offset specifies the number of prefix nops between the KCFI type hash and the function entry when -Z patchable-function-entry is used. Note that LLVM assumes all indirectly callable functions use the same number of prefix NOPs with -Zsanitizer=kcfi.
Set the cfi-normalize-integers and kcfi-offset module flags when
Control-Flow Integrity sanitizers are used, so functions generated by
the LLVM backend use the same CFI/KCFI options as rustc.
cfi-normalize-integers tells LLVM to also use integer normalization
for generated functions when -Zsanitizer-cfi-normalize-integers is
used.
kcfi-offset specifies the number of prefix nops between the KCFI
type hash and the function entry when -Z patchable-function-entry is
used. Note that LLVM assumes all indirectly callable functions use the
same number of prefix NOPs with -Zsanitizer=kcfi.
llvm-wrapper: adapt for LLVM 20 API changes
No functional changes intended.
Adapts llvm-wrapper for the LLVM commits 0f22d47a7a and d6d8243dcd.
`@rustbot` label: +llvm-main
r? `@nikic`
bump conflicting_repr_hints lint to be shown in dependencies
This has been a future compatibility lint for years, let's bump it up to be shown in dependencies (so that hopefully we can then make it a hard error fairly soon).
Cc https://github.com/rust-lang/rust/issues/68585
Point at explicit `'static` obligations on a trait
Given `trait Any: 'static` and a `struct` with a `Box<dyn Any + 'a>` field, point at the `'static` bound in `Any` to explain why `'a: 'static`.
```
error[E0478]: lifetime bound not satisfied
--> f202.rs:2:12
|
2 | value: Box<dyn std::any::Any + 'a>,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: lifetime parameter instantiated with the lifetime `'a` as defined here
--> f202.rs:1:14
|
1 | struct Hello<'a> {
| ^^
note: but lifetime parameter must outlive the static lifetime
--> /home/gh-estebank/rust/library/core/src/any.rs:113:16
|
113 | pub trait Any: 'static {
| ^^^^^^^
```
Partially address #33652.
Improve diagnostic-related lints: `untranslatable_diagnostic` & `diagnostic_outside_of_impl`
Summary:
- Made `untranslatable_diagnostic` point to problematic arguments instead of the function call
(I found this misleading while working on some `A-translation` PRs: my first impression was that
the methods themselves were not translation-aware and needed to be changed,
while in reality the problem was with the hardcoded strings passed as arguments).
- Made the shared pass of `untranslatable_diagnostic` & `diagnostic_outside_of_impl` more efficient.
`@rustbot` label D-imprecise-spans A-translation
use old ctx if has same expand environment during decode span
Fixes#112680
The root reason why #112680 failed with incremental compilation on the second attempt is the difference in `opaque` between the span of the field [`ident`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_hir_typeck/src/expr.rs#L2348) and the span in the incremental cache at `tcx.def_ident_span(field.did)`.
- Let's call the span of `ident` as `span_a`, which is generated by [`apply_mark_internal`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_span/src/hygiene.rs#L553-L554). Its content is similar to:
```rs
span_a_ctx -> SyntaxContextData {
opaque: span_a_ctx,
opaque_and_semitransparent: span_a_ctx,
// ....
}
```
- And call the span of `tcx.def_ident_span` as `span_b`, which is generated by [`decode_syntax_context`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_span/src/hygiene.rs#L1390). Its content is:
```rs
span_b_ctx -> SyntaxContextData {
opaque: span_b_ctx,
// note `span_b_ctx` is not same as `span_a_ctx`
opaque_and_semitransparent: span_b_ctx,
// ....
}
```
Although they have the same `parent` (both refer to the root) and `outer_expn`, I cannot find the specific connection between them. Therefore, I chose a solution that may not be the best: give up the incremental compile cache to ensure we can use `span_a` in this case.
r? `@petrochenkov` Do you have any advice on this? Or perhaps this solution is acceptable?
Given `trait Any: 'static` and a `struct` with a `Box<dyn Any + 'a>` field, point at the `'static` bound in `Any` to explain why `'a: 'static`.
```
error[E0478]: lifetime bound not satisfied
--> f202.rs:2:12
|
2 | value: Box<dyn std::any::Any + 'a>,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: lifetime parameter instantiated with the lifetime `'a` as defined here
--> f202.rs:1:14
|
1 | struct Hello<'a> {
| ^^
note: but lifetime parameter must outlive the static lifetime
--> /home/gh-estebank/rust/library/core/src/any.rs:113:16
|
113 | pub trait Any: 'static {
| ^^^^^^^
```
Partially address #33652.
Use shorthand field initialization syntax more aggressively in the compiler
Caught these when cleaning up #129344 and decided to run clippy to find the rest
Use `bool` in favor of `Option<()>` for diagnostics
We originally only supported `Option<()>` for optional notes/labels, but we now support `bool`. Let's use that, since it usually leads to more readable code.
I'm not removing the support from the derive macro, though I guess we could error on it... 🤔
Make `ArgAbi::make_indirect_force` more specific
As the method is only needed for making ignored ZSTs indirect on some ABIs, rename and add a doc-comment and `self.mode` check to make it harder to accidentally misuse. Addresses review feedback from https://github.com/rust-lang/rust/pull/125854#discussion_r1721047899.
r? ``@RalfJung``
Avoid extra `cast()`s after `CStr::as_ptr()`
These used to be `&str` literals that did need a pointer cast, but that
became a no-op after switching to `c""` literals in #118566.
CFI: Erase regions when projecting ADT to its transparent non-1zst field
The output from `FieldDef::ty` (or `TyCtxt::type_of`) may have free regions (well, `'static`) -- erase it.
Fixes#129169Fixes#123685
Minor Refactor: Remove a Redundant Conditional Check
The existing code checks `where_bounds.is_empty()` twice when
it can be combined into one. Now, after combining, the refactored code reads
better and feels straightforward.
The diff doesn't make it clear. So, the current code looks like this:
``` rust
if !where_bounds.is_empty() {
err.help(format!(
"consider introducing a new type parameter `T` and adding `where` constraints:\
\n where\n T: {qself_str},\n{}",
where_bounds.join(",\n"),
));
}
let reported = err.emit();
if !where_bounds.is_empty() {
return Err(reported);
}
```
The proposed changes:
``` rust
if !where_bounds.is_empty() {
err.help(format!(
"consider introducing a new type parameter `T` and adding `where` constraints:\
\n where\n T: {qself_str},\n{}",
where_bounds.join(",\n"),
));
let reported = err.emit();
return Err(reported);
}
err.emit();
```
Special case DUMMY_SP to emit line 0/column 0 locations on DWARF platforms.
Line 0 has a special meaning in DWARF. From the version 5 spec:
The compiler may emit the value 0 in cases
where an instruction cannot be attributed to any
source line.
DUMMY_SP spans cannot be attributed to any line. However, because rustc internally stores line numbers starting at zero, lookup_debug_loc() adjusts every line number by one. Special casing DUMMY_SP to actually emit line 0 ensures rustc communicates to the debugger that there's no meaningful source code for this instruction, rather than telling the debugger to jump to line 1 randomly.
fix a broken link in `mir/mod.rs`
I discovered that the internal link in mir/mod.rs is broken, so I will fix it. The AddCallGuards is now located under rustc_mir_transform.
The PR at that time is as follows.
c5fc2609f0
ctfe: make CompileTimeInterpCx type alias public
`CompileTimeMachine` is already public so there is no good reason to not also make this public.
Also add comment explaining why `CompileTimeMachine` is public.
Don't consider locals to shadow inner items' generics
We don't want to consider the bindings from a `RibKind::Module` itself, because for an inner item that module will contain the local bindings from the function body or wherever else the inner item is being defined.
Fixes#129265
r? petrochenkov
skip updating when external binding is existed
Fixes#128813
For following code:
```rs
extern crate core;
fn f() {
use ::core;
}
macro_rules! m {
() => {
extern crate std as core;
};
}
m!();
fn main() {}
```
- In the first loop, we define `extern crate core` and `use ::core` will be referred to `core` (yes, it does not consider if there are some macros that are not expanded. Ideally, this should be delayed if there are some unexpanded macros in the root, but I didn't change it like that because it seems like a huge change).
- Then `m` is expanded, which makes `extern_prelude('core')` return `std` rather than `core`, causing the inconsistency.
r? `@petrochenkov`
Don't generate functions with the `rustc_intrinsic_must_be_overridden` attribute
Functions with the attribute `rustc_intrinsic_must_be_overridden` never be called.
r? compiler
Stabilize opaque type precise capturing (RFC 3617)
This PR partially stabilizes opaque type *precise capturing*, which was specified in [RFC 3617](https://github.com/rust-lang/rfcs/pull/3617), and whose syntax was amended by FCP in [#125836](https://github.com/rust-lang/rust/issues/125836).
This feature, as stabilized here, gives us a way to explicitly specify the generic lifetime parameters that an RPIT-like opaque type captures. This solves the problem of overcapturing, for lifetime parameters in these opaque types, and will allow the Lifetime Capture Rules 2024 ([RFC 3498](https://github.com/rust-lang/rfcs/pull/3498)) to be fully stabilized for RPIT in Rust 2024.
### What are we stabilizing?
This PR stabilizes the use of a `use<'a, T>` bound in return-position impl Trait opaque types. Such a bound fully specifies the set of generic parameters captured by the RPIT opaque type, entirely overriding the implicit default behavior. E.g.:
```rust
fn does_not_capture<'a, 'b>() -> impl Sized + use<'a> {}
// ~~~~~~~~~~~~~~~~~~~~
// This RPIT opaque type does not capture `'b`.
```
The way we would suggest thinking of `impl Trait` types *without* an explicit `use<..>` bound is that the `use<..>` bound has been *elided*, and that the bound is filled in automatically by the compiler according to the edition-specific capture rules.
All non-`'static` lifetime parameters, named (i.e. non-APIT) type parameters, and const parameters in scope are valid to name, including an elided lifetime if such a lifetime would also be valid in an outlives bound, e.g.:
```rust
fn elided(x: &u8) -> impl Sized + use<'_> { x }
```
Lifetimes must be listed before type and const parameters, but otherwise the ordering is not relevant to the `use<..>` bound. Captured parameters may not be duplicated. For now, only one `use<..>` bound may appear in a bounds list. It may appear anywhere within the bounds list.
### How does this differ from the RFC?
This stabilization differs from the RFC in one respect: the RFC originally specified `use<'a, T>` as syntactically part of the RPIT type itself, e.g.:
```rust
fn capture<'a>() -> impl use<'a> Sized {}
```
However, settling on the final syntax was left as an open question. T-lang later decided via FCP in [#125836](https://github.com/rust-lang/rust/issues/125836) to treat `use<..>` as a syntactic bound instead, e.g.:
```rust
fn capture<'a>() -> impl Sized + use<'a> {}
```
### What aren't we stabilizing?
The key goal of this PR is to stabilize the parts of *precise capturing* that are needed to enable the migration to Rust 2024.
There are some capabilities of *precise capturing* that the RFC specifies but that we're not stabilizing here, as these require further work on the type system. We hope to lift these limitations later.
The limitations that are part of this PR were specified in the [RFC's stabilization strategy](https://rust-lang.github.io/rfcs/3617-precise-capturing.html#stabilization-strategy).
#### Not capturing type or const parameters
The RFC addresses the overcapturing of type and const parameters; that is, it allows for them to not be captured in opaque types. We're not stabilizing that in this PR. Since all in scope generic type and const parameters are implicitly captured in all editions, this is not needed for the migration to Rust 2024.
For now, when using `use<..>`, all in scope type and const parameters must be nameable (i.e., APIT cannot be used) and included as arguments. For example, this is an error because `T` is in scope and not included as an argument:
```rust
fn test<T>() -> impl Sized + use<> {}
//~^ ERROR `impl Trait` must mention all type parameters in scope in `use<...>`
```
This is due to certain current limitations in the type system related to how generic parameters are represented as captured (i.e. bivariance) and how inference operates.
We hope to relax this in the future, and this stabilization is forward compatible with doing so.
#### Precise capturing for return-position impl Trait **in trait** (RPITIT)
The RFC specifies precise capturing for RPITIT. We're not stabilizing that in this PR. Since RPITIT already adheres to the Lifetime Capture Rules 2024, this isn't needed for the migration to Rust 2024.
The effect of this is that the anonymous associated types created by RPITITs must continue to capture all of the lifetime parameters in scope, e.g.:
```rust
trait Foo<'a> {
fn test() -> impl Sized + use<Self>;
//~^ ERROR `use<...>` precise capturing syntax is currently not allowed in return-position `impl Trait` in traits
}
```
To allow this involves a meaningful amount of type system work related to adding variance to GATs or reworking how generics are represented in RPITITs. We plan to do this work separately from the stabilization. See:
- https://github.com/rust-lang/rust/pull/124029
Supporting precise capturing for RPITIT will also require us to implement a new algorithm for detecting refining capture behavior. This may involve looking through type parameters to detect cases where the impl Trait type in an implementation captures fewer lifetimes than the corresponding RPITIT in the trait definition, e.g.:
```rust
trait Foo {
fn rpit() -> impl Sized + use<Self>;
}
impl<'a> Foo for &'a () {
// This is "refining" due to not capturing `'a` which
// is implied by the trait's `use<Self>`.
fn rpit() -> impl Sized + use<>;
// This is not "refining".
fn rpit() -> impl Sized + use<'a>;
}
```
This stabilization is forward compatible with adding support for this later.
### The technical details
This bound is purely syntactical and does not lower to a [`Clause`](https://doc.rust-lang.org/1.79.0/nightly-rustc/rustc_middle/ty/type.ClauseKind.html) in the type system. For the purposes of the type system (and for the types team's curiosity regarding this stabilization), we have no current need to represent this as a `ClauseKind`.
Since opaques already capture a variable set of lifetimes depending on edition and their syntactical position (e.g. RPIT vs RPITIT), a `use<..>` bound is just a way to explicitly rather than implicitly specify that set of lifetimes, and this only affects opaque type lowering from AST to HIR.
### FCP plan
While there's much discussion of the type system here, the feature in this PR is implemented internally as a transformation that happens before lowering to the type system layer. We already support impl Trait types partially capturing the in scope lifetimes; we just currently only expose that implicitly.
So, in my (errs's) view as a types team member, there's nothing for types to weigh in on here with respect to the implementation being stabilized, and I'd suggest a lang-only proposed FCP (though we'll of course CC the team below).
### Authorship and acknowledgments
This stabilization report was coauthored by compiler-errors and TC.
TC would like to acknowledge the outstanding and speedy work that compiler-errors has done to make this feature happen.
compiler-errors thanks TC for authoring the RFC, for all of his involvement in this feature's development, and pushing the Rust 2024 edition forward.
### Open items
We're doing some things in parallel here. In signaling the intention to stabilize, we want to uncover any latent issues so we can be sure they get addressed. We want to give the maximum time for discussion here to happen by starting it while other remaining miscellaneous work proceeds. That work includes:
- [x] Look into `syn` support.
- https://github.com/dtolnay/syn/issues/1677
- https://github.com/dtolnay/syn/pull/1707
- [x] Look into `rustfmt` support.
- https://github.com/rust-lang/rust/pull/126754
- [x] Look into `rust-analyzer` support.
- https://github.com/rust-lang/rust-analyzer/issues/17598
- https://github.com/rust-lang/rust-analyzer/pull/17676
- [x] Look into `rustdoc` support.
- https://github.com/rust-lang/rust/issues/127228
- https://github.com/rust-lang/rust/pull/127632
- https://github.com/rust-lang/rust/pull/127658
- [x] Suggest this feature to RfL (a known nightly user).
- [x] Add a chapter to the edition guide.
- https://github.com/rust-lang/edition-guide/pull/316
- [x] Update the Reference.
- https://github.com/rust-lang/reference/pull/1577
### (Selected) implementation history
* https://github.com/rust-lang/rfcs/pull/3498
* https://github.com/rust-lang/rfcs/pull/3617
* https://github.com/rust-lang/rust/pull/123468
* https://github.com/rust-lang/rust/issues/125836
* https://github.com/rust-lang/rust/pull/126049
* https://github.com/rust-lang/rust/pull/126753Closes#123432.
cc `@rust-lang/lang` `@rust-lang/types`
`@rustbot` labels +T-lang +I-lang-nominated +A-impl-trait +F-precise_capturing
Tracking:
- https://github.com/rust-lang/rust/issues/123432
----
For the compiler reviewer, I'll leave some inline comments about diagnostics fallout :^)
r? compiler
Added "copy" to Debug fmt for copy operands
In MIR's debug mode (--emit mir) the printing for Operands is slightly inconsistent.
The RValues - values on the right side of an Assign - are usually printed with their Operand when they are Places.
Example:
_2 = move _3
But for arguments, the operand is omitted.
_2 = _1
I propose a change be made, to display the place with the operand.
_2 = copy _1
Move and copy have different semantics, meaning this difference is important and helpful to the user. It also adds consistency to the pretty printing.
-- EDIT --
Consider this example Rust program and its MIR output with the **updated pretty printer.**
This was generated with the arguments --emit mir --crate-type lib -Zmir-opt-level=0 (Otherwise, it's optimised away since it's a junk program).
```rust
fn main(foo: i32) {
let v = 10;
if v == 20 {
foo;
}
else {
v;
}
}
```
```MIR
// WARNING: This output format is intended for human consumers only
// and is subject to change without notice. Knock yourself out.
fn main(_1: i32) -> () {
debug foo => _1;
let mut _0: ();
let _2: i32;
let mut _3: bool;
let mut _4: i32;
let _5: i32;
let _6: i32;
scope 1 {
debug v => _2;
}
bb0: {
StorageLive(_2);
_2 = const 10_i32;
StorageLive(_3);
StorageLive(_4);
_4 = copy _2;
_3 = Eq(move _4, const 20_i32);
switchInt(move _3) -> [0: bb2, otherwise: bb1];
}
bb1: {
StorageDead(_4);
StorageLive(_5);
_5 = copy _1;
StorageDead(_5);
_0 = const ();
goto -> bb3;
}
bb2: {
StorageDead(_4);
StorageLive(_6);
_6 = copy _2;
StorageDead(_6);
_0 = const ();
goto -> bb3;
}
bb3: {
StorageDead(_3);
StorageDead(_2);
return;
}
}
```
In this example program, we can see that when we move a place, it is preceded by "move". e.g. ``` _3 = Eq(move _4, const 20_i32);```. However, when we copy a place such as ```_5 = _1;```, it is not preceded by the operand in the original printout. I propose to change the print to include the copy ```_5 = copy _1``` as in this example.
Regarding the arguments part. When I originally submitted this PR, I was under the impression this only affected the print for arguments to a function, but actually, it affects anything that uses a copy. This is preferable anyway with regard to consistency. The PR is about making ```copy``` explicit.
