Output correct type responsible for structural match violation
Previously we included the outermost type that caused a structural match violation in the error message and stated that that type must be annotated with `#[derive(Eq, PartialEq)]` even if it already had that annotation. This PR outputs the correct type in the error message.
Fixes https://github.com/rust-lang/rust/issues/97278
Do writeback of Closure params before visiting the parent expression
This means that given the expression:
```
let x = |a: Vec<_>| {};
```
We will visit the HIR node for `a` before `x`, and report the ambiguity on the former instead of the latter. This also moves writeback for struct field ids and const blocks before, but the ordering of this and walking the expr doesn't seem to matter.
This is a >= condition, so we need a maximum size of 7 to not
create a stack protector in basic mode.
The reason this still worked is that the alloca type was converted
into an integer (rather than an array). The way these heuristics
are implemented in LLVM is rather questionable and not resilient
to optimization.
This was relying on the presence of a bitcast to avoid using the
constant global initializer for a load using a different type.
With opaque pointers, we need to check this explicitly.
Extend ptr::null and null_mut to all thin (including extern) types
Fixes https://github.com/rust-lang/rust/issues/93959
This change was accepted in https://rust-lang.github.io/rfcs/2580-ptr-meta.html
Note that this changes the signature of **stable** functions. The change should be backward-compatible, but it is **insta-stable** since it cannot (easily, at all?) be made available only through a `#![feature(…)]` opt-in.
The RFC also proposed the same change for `NonNull::dangling`, which makes sense it terms of its signature but not in terms of its implementation. `dangling` uses `align_of()` as an address. But what `align_of()` should be for extern types or whether it should be allowed at all remains an open question.
This commit depends on https://github.com/rust-lang/rust/pull/93977, which is not yet part of the bootstrap compiler. So `#[cfg]` is used to only apply the change in stage 1+. As far a I know bounds cannot be made conditional with `#[cfg]`, so the entire functions are duplicated. This is unfortunate but temporary.
Since this duplication makes it less obvious in the diff, the new definitions differ in:
* More permissive bounds (`Thin` instead of implied `Sized`)
* Different implementation
* Having `rustc_allow_const_fn_unstable(const_fn_trait_bound)`
* Having `rustc_allow_const_fn_unstable(ptr_metadata)`
Minor improvement on else-no-if diagnostic
Don't suggest wrapping in block since it's highly likely to be a missing `if` after `else`. Also rework message a bit (open to further suggestions).
cc: https://github.com/rust-lang/rust/pull/97298#discussion_r880933431
r? `@estebank`
[RFC 2011] Library code
CC https://github.com/rust-lang/rust/pull/96496
Based on https://github.com/dtolnay/case-studies/tree/master/autoref-specialization.
Basically creates two traits with the same method name. One trait is generic over any `T` and the other is specialized to any `T: Printable`.
The compiler will then call the corresponding trait method through auto reference.
```rust
fn main() {
let mut a = Capture::new();
let mut b = Capture::new();
(&Wrapper(&1i32)).try_capture(&mut a); // `try_capture` from `TryCapturePrintable`
(&Wrapper(&vec![1i32])).try_capture(&mut b); // `try_capture` from `TryCaptureGeneric`
assert_eq!(format!("{:?}", a), "1");
assert_eq!(format!("{:?}", b), "N/A");
}
```
r? `@scottmcm`
RFC3239: Implement `cfg(target)` - Part 2
This pull-request implements the compact `cfg(target(..))` part of [RFC 3239](https://github.com/rust-lang/rust/issues/96901).
I recommend reviewing this PR on a per commit basics, because of some moving parts.
cc `@GuillaumeGomez`
r? `@petrochenkov`
Modify MIR building to drop repeat expressions with length zero
Closes#74836 .
Previously, when a user wrote `[foo; 0]` we used to simply leak `foo`. The goal is to fix that. This PR changes MIR building to make `[foo; 0]` equivalent to `{ drop(foo); [] }` in all cases. Of course, this is a breaking change (see below). A crater run did not indicate any regressions though, and given that the previous behavior was almost definitely not what any user wanted, it seems unlikely that anyone was relying on this.
Note that const generics are in general unaffected by this. Inserting the extra `drop` is only meaningful/necessary when `foo` is of a non-`Copy` type, and array repeat expressions with const generic repetition count must always be `Copy`.
Besides the obvious change to behavior associated with the additional drop, there are three categories of examples where this also changes observable behavior. In all of these cases, the new behavior is consistent with what you would get by replacing `[foo; 0]` with `{ drop(foo); [] }`. As such, none of these give the user new powers to express more things.
**No longer allowed in const (breaking)**:
```rust
const _: [String; 0] = [String::new(); 0];
```
This compiles on stable today. Because we now introduce the drop of `String`, this no longer compiles as `String` may not be dropped in a const context.
**Reduced dataflow (non-breaking)**:
```rust
let mut x: i32 = 0;
let r = &x;
let a = [r; 0];
x = 5;
let _b = a;
```
Borrowck rejects this code on stable because it believes there is dataflow between `a` and `r`, and so the lifetime of `r` has to extend to the last statement. This change removes the dataflow and the above code is allowed to compile.
**More const promotion (non-breaking)**:
```rust
let _v: &'static [String; 0] = &[String::new(); 0];
```
This does not compile today because `String` having drop glue keeps it from being const promoted (despite that drop glue never being executed). After this change, this is allowed to compile.
### Alternatives
A previous attempt at this tried to reduce breakage by various tricks. This is still a possibility, but given that crater showed no regressions it seems unclear why we would want to introduce this complexity.
Disallowing `[foo; 0]` completely is also an option, but obviously this is more of a breaking change. I do not know how often this is actually used though.
r? `@oli-obk`
add a deep fast_reject routine
continues the work on #97136.
r? `@nnethercote`
Actually agree with you on the match structure 😆 let's see how that impacted perf 😅
Rollup of 5 pull requests
Successful merges:
- #93604 (Make llvm-libunwind a per-target option)
- #97026 (Change orderings of `Debug` for the Atomic types to `Relaxed`.)
- #97105 (Add tests for lint on type dependent on consts)
- #97323 (Introduce stricter checks for might_permit_raw_init under a debug flag )
- #97379 (Add aliases for `current_dir`)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
`match_impl` has two call sites. For one of them (within `rematch_impl`)
the fast reject test isn't necessary, because any rejection would
represent a compiler bug.
This commit moves the fast reject test to the other `match_impl` call
site, in `assemble_candidates_from_impls`. This lets us move the fast
reject test outside the `probe` call in that function. This avoids the
taking of useless snapshots when the fast reject test succeeds, which
gives a performance win when compiling the `bitmaps` and `nalgebra`
crates.
Co-authored-by: name <n.nethercote@gmail.com>
Add aliases for `current_dir`
Aliases were added for the equivalent C/C++ APIs for POSIX and Windows. Also, I added one for `pwd` which users may be more familiar with, from the command line.
Introduce stricter checks for might_permit_raw_init under a debug flag
This is intended to be a version of the strict checks tried out in #79296, but also checking number validity (under the assumption that `let _ = std::mem::uninitialized::<u32>()` is UB, which seems to be what https://github.com/rust-lang/unsafe-code-guidelines/issues/71 is leaning towards.)
Change orderings of `Debug` for the Atomic types to `Relaxed`.
This reduces synchronization between threads when debugging the atomic types. Reducing the synchronization means that executions with and without the debug calls will be more consistent, making it easier to debug.
We discussed this on the Rust Community Discord with `@ibraheemdev` before.
Make `Lazy*<T>` types in `rustc_metadata` not care about lifetimes until decode
This allows us to remove the `'tcx` lifetime from `CrateRoot`. This is necessary because of #97287, which makes the `'tcx` lifetime on `Ty` invariant instead of covariant, so [this hack](0a437b2ca0/compiler/rustc_metadata/src/rmeta/decoder.rs (L89-92)) no longer holds under that PR.
Introduces a trait called `ParameterizedOverTcx` which has a generic associated type that allows a type to be parameterized over that lifetime. This means we can decode, for example, `Lazy<Ty<'static>>` into any `Ty<'tcx>` depending on the `TyCtxt<'tcx>` we pass into the decode function.
