```
error[E0499]: cannot borrow `foo` as mutable more than once at a time
--> $DIR/suggest-split-at-mut.rs:13:18
|
LL | let a = &mut foo[..2];
| --- first mutable borrow occurs here
LL | let b = &mut foo[2..];
| ^^^ second mutable borrow occurs here
LL | a[0] = 5;
| ---- first borrow later used here
|
= help: use `.split_at_mut(position)` or similar method to obtain two mutable non-overlapping sub-slices
```
Address most of #58792.
For follow up work, we should emit a structured suggestion for cases where we can identify the exact `let (a, b) = foo.split_at_mut(2);` call that is needed.
Set writable and dead_on_unwind attributes for sret arguments
Set the `writable` and `dead_on_unwind` attributes for `sret` arguments. This allows call slot optimization to remove more memcpy's.
See https://llvm.org/docs/LangRef.html#parameter-attributes for the specification of these attributes. In short, the statement we're making here is that:
* The return slot is writable.
* The return slot will not be read if the function unwinds.
Fixes https://github.com/rust-lang/rust/issues/90595.
Rewrite the `no-input-file.stderr` test in Rust and support diff
Rewrite the `no-input-file.stderr` test from #121876.
Use the `similar` lib to replace the `diff` command.
Provide more context and suggestions in borrowck errors involving closures
Start pointing to where bindings where declared when they are captured in closures:
```
error[E0597]: `x` does not live long enough
--> $DIR/suggest-return-closure.rs:23:9
|
LL | let x = String::new();
| - binding `x` declared here
...
LL | |c| {
| --- value captured here
LL | x.push(c);
| ^ borrowed value does not live long enough
...
LL | }
| -- borrow later used here
| |
| `x` dropped here while still borrowed
```
Suggest cloning in more cases involving closures:
```
error[E0507]: cannot move out of `foo` in pattern guard
--> $DIR/issue-27282-move-ref-mut-into-guard.rs:11:19
|
LL | if { (|| { let mut bar = foo; bar.take() })(); false } => {},
| ^^ --- move occurs because `foo` has type `&mut Option<&i32>`, which does not implement the `Copy` trait
| |
| `foo` is moved here
|
= note: variables bound in patterns cannot be moved from until after the end of the pattern guard
help: consider cloning the value if the performance cost is acceptable
|
LL | if { (|| { let mut bar = foo.clone(); bar.take() })(); false } => {},
| ++++++++
```
Mention when type parameter could be Clone
```
error[E0382]: use of moved value: `t`
--> $DIR/use_of_moved_value_copy_suggestions.rs:7:9
|
LL | fn duplicate_t<T>(t: T) -> (T, T) {
| - move occurs because `t` has type `T`, which does not implement the `Copy` trait
...
LL | (t, t)
| - ^ value used here after move
| |
| value moved here
|
help: if `T` implemented `Clone`, you could clone the value
--> $DIR/use_of_moved_value_copy_suggestions.rs:4:16
|
LL | fn duplicate_t<T>(t: T) -> (T, T) {
| ^ consider constraining this type parameter with `Clone`
...
LL | (t, t)
| - you could clone this value
help: consider restricting type parameter `T`
|
LL | fn duplicate_t<T: Copy>(t: T) -> (T, T) {
| ++++++
```
The `help` is new. On ADTs, we also extend the output with span labels:
```
error[E0507]: cannot move out of static item `FOO`
--> $DIR/issue-17718-static-move.rs:6:14
|
LL | let _a = FOO;
| ^^^ move occurs because `FOO` has type `Foo`, which does not implement the `Copy` trait
|
note: if `Foo` implemented `Clone`, you could clone the value
--> $DIR/issue-17718-static-move.rs:1:1
|
LL | struct Foo;
| ^^^^^^^^^^ consider implementing `Clone` for this type
...
LL | let _a = FOO;
| --- you could clone this value
help: consider borrowing here
|
LL | let _a = &FOO;
| +
```
Suggest cloning captured binding in move closure
```
error[E0507]: cannot move out of `bar`, a captured variable in an `FnMut` closure
--> $DIR/borrowck-move-by-capture.rs:9:29
|
LL | let bar: Box<_> = Box::new(3);
| --- captured outer variable
LL | let _g = to_fn_mut(|| {
| -- captured by this `FnMut` closure
LL | let _h = to_fn_once(move || -> isize { *bar });
| ^^^^^^^^^^^^^^^^ ----
| | |
| | variable moved due to use in closure
| | move occurs because `bar` has type `Box<isize>`, which does not implement the `Copy` trait
| `bar` is moved here
|
help: clone the value before moving it into the closure 1
|
LL ~ let value = bar.clone();
LL ~ let _h = to_fn_once(move || -> isize { value });
|
```
```
error[E0507]: cannot move out of `bar`, a captured variable in an `FnMut` closure
--> $DIR/borrowck-move-by-capture.rs:9:29
|
LL | let bar: Box<_> = Box::new(3);
| --- captured outer variable
LL | let _g = to_fn_mut(|| {
| -- captured by this `FnMut` closure
LL | let _h = to_fn_once(move || -> isize { *bar });
| ^^^^^^^^^^^^^^^^ ----
| | |
| | variable moved due to use in closure
| | move occurs because `bar` has type `Box<isize>`, which does not implement the `Copy` trait
| `bar` is moved here
|
help: clone the value before moving it into the closure
|
LL ~ let value = bar.clone();
LL ~ let _h = to_fn_once(move || -> isize { value });
|
```
```
error[E0382]: use of moved value: `t`
--> $DIR/use_of_moved_value_copy_suggestions.rs:7:9
|
LL | fn duplicate_t<T>(t: T) -> (T, T) {
| - move occurs because `t` has type `T`, which does not implement the `Copy` trait
...
LL | (t, t)
| - ^ value used here after move
| |
| value moved here
|
help: if `T` implemented `Clone`, you could clone the value
--> $DIR/use_of_moved_value_copy_suggestions.rs:4:16
|
LL | fn duplicate_t<T>(t: T) -> (T, T) {
| ^ consider constraining this type parameter with `Clone`
...
LL | (t, t)
| - you could clone this value
help: consider restricting type parameter `T`
|
LL | fn duplicate_t<T: Copy>(t: T) -> (T, T) {
| ++++++
```
The `help` is new. On ADTs, we also extend the output with span labels:
```
error[E0507]: cannot move out of static item `FOO`
--> $DIR/issue-17718-static-move.rs:6:14
|
LL | let _a = FOO;
| ^^^ move occurs because `FOO` has type `Foo`, which does not implement the `Copy` trait
|
note: if `Foo` implemented `Clone`, you could clone the value
--> $DIR/issue-17718-static-move.rs:1:1
|
LL | struct Foo;
| ^^^^^^^^^^ consider implementing `Clone` for this type
...
LL | let _a = FOO;
| --- you could clone this value
help: consider borrowing here
|
LL | let _a = &FOO;
| +
```
Start pointing to where bindings were declared when they are captured in closures:
```
error[E0597]: `x` does not live long enough
--> $DIR/suggest-return-closure.rs:23:9
|
LL | let x = String::new();
| - binding `x` declared here
...
LL | |c| {
| --- value captured here
LL | x.push(c);
| ^ borrowed value does not live long enough
...
LL | }
| -- borrow later used here
| |
| `x` dropped here while still borrowed
```
Suggest cloning in more cases involving closures:
```
error[E0507]: cannot move out of `foo` in pattern guard
--> $DIR/issue-27282-move-ref-mut-into-guard.rs:11:19
|
LL | if { (|| { let mut bar = foo; bar.take() })(); false } => {},
| ^^ --- move occurs because `foo` has type `&mut Option<&i32>`, which does not implement the `Copy` trait
| |
| `foo` is moved here
|
= note: variables bound in patterns cannot be moved from until after the end of the pattern guard
help: consider cloning the value if the performance cost is acceptable
|
LL | if { (|| { let mut bar = foo.clone(); bar.take() })(); false } => {},
| ++++++++
```
Improve diagnostic for unknown `--print` request
This PR improves the diagnostic when encountering a unknown `--print` request.
It also moves the run-make test to a simple UI test.
Stabilise inline_const
# Stabilisation Report
## Summary
This PR will stabilise `inline_const` feature in expression position. `inline_const_pat` is still unstable and will *not* be stabilised.
The feature will allow code like this:
```rust
foo(const { 1 + 1 })
```
which is roughly desugared into
```rust
struct Foo;
impl Foo {
const FOO: i32 = 1 + 1;
}
foo(Foo::FOO)
```
This feature is from https://github.com/rust-lang/rfcs/pull/2920 and is tracked in #76001 (the tracking issue should *not* be closed as it needs to track inline const in pattern position). The initial implementation is done in #77124.
## Difference from RFC
There are two major differences (enhancements) as implemented from the RFC. First thing is that the RFC says that the type of an inline const block inferred from the content *within* it, but we currently can infer the type using the information from outside the const block as well. This is a frequently requested feature to the initial implementation (e.g. #89964). The inference is implemented in #89561 and is done by treating inline const similar to a closure and therefore share inference context with its parent body.
This allows code like:
```rust
let v: Vec<i32> = const { Vec::new() };
```
Another enhancement that differs from the RFC is that we currently allow inline consts to reference generic parameters. This is implemented in #96557.
This allows code like:
```rust
fn create_none_array<T, const N: usize>() -> [Option<T>; N] {
[const { None::<T> }; N]
}
```
This enhancement also makes inline const usable as static asserts:
```rust
fn require_zst<T>() {
const { assert!(std::mem::size_of::<T>() == 0) }
}
```
## Documentation
Reference: rust-lang/reference#1295
## Unresolved issues
We still have a few issues that are not resolved, but I don't think it necessarily has to block stabilisation:
* expr fragment specifier issue: #86730
* ~~`const {}` behaves similar to `async {}` but not to `{}` and `unsafe {}` (they are treated as `ExpressionWithoutBlock` rather than `ExpressionWithBlock`): https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/const.20blocks.20differ.20from.20normal.20and.20from.20unsafe.20blocks/near/290229453~~
## Tests
There are a few tests in https://github.com/rust-lang/rust/tree/master/src/test/ui/inline-const
More DefineOpaqueTypes::Yes
This accepts more code on stable. It is now possible to have match arms return a function item `foo::<ConcreteType>` and a function item `foo::<OpaqueTypeInDefiningScope>` in another, and that will constrain `OpaqueTypeInDefiningScope` to have the hidden type `ConcreteType`. So the following function will now compile, but on master it errors with a type mismatch on the second match arm
```rust
// The function item whose generic params we want to merge.
fn foo<T>(t: T) -> T { t }
// Helper ensuring we can constrain `T` on `F` without explicitly specifying it
fn bind<T, F: FnOnce(T) -> T>(_: T, f: F) -> F { f }
fn k() -> impl Sized {
let x = match true {
true => {
// `f` is `FnDef(foo, [infer_var])`
let f = foo;
// Get a value of an opaque type on stable
let t = k();
// this returns `FnDef(foo, [k::return])`
bind(t, f)
}
false => foo::<()>,
};
todo!()
}
```
r? ``@compiler-errors``
cc https://github.com/rust-lang/rust/issues/116652
Test `#[unix_sigpipe = "inherit"]` with both `SIG_DFL` and `SIG_IGN`
Extend our `#[unix_sigpipe = "inherit"]` test so that it detects if `SIGPIPE` wrongly ends up being `SIG_DFL` when the parent has `SIG_IGN`. We have no current test for this particular case.
Tracking issue: https://github.com/rust-lang/rust/issues/97889
delegation: Support renaming, and async, const, extern "ABI" and C-variadic functions
Also allow delegating to functions with opaque types (`impl Trait`).
The delegation item will refer to the original opaque type from the callee, fresh opaque type won't be created, which seems like a reasonable behavior.
(Such delegation items will cause query cycles when used in trait impls, but it can be fixed later.)
Part of https://github.com/rust-lang/rust/issues/118212.
Stop using LLVM struct types for alloca
The alloca type has no semantic meaning, only the size (and alignment, but we specify it explicitly) matter. Using `[N x i8]` is a more direct way to specify that we want `N` bytes, and avoids relying on LLVM's struct layout. It is likely that a future LLVM version will change to an untyped alloca representation.
Split out from #121577.
r? `@ghost`
Also allow `impl Trait` in delegated functions.
The delegation item will refer to the original opaque type from the callee, fresh opaque type won't be created.
Rollup of 3 pull requests
Successful merges:
- #124003 (Dellvmize some intrinsics (use `u32` instead of `Self` in some integer intrinsics))
- #124169 (Don't fatal when calling `expect_one_of` when recovering arg in `parse_seq`)
- #124286 (Subtree sync for rustc_codegen_cranelift)
r? `@ghost`
`@rustbot` modify labels: rollup
Don't fatal when calling `expect_one_of` when recovering arg in `parse_seq`
In `parse_seq`, when parsing a sequence of token-separated items, if we don't see a separator, we try to parse another item eagerly in order to give a good diagnostic and recover from a missing separator:
d1a0fa5ed3/compiler/rustc_parse/src/parser/mod.rs (L900-L901)
If parsing the item itself calls `expect_one_of`, then we will fatal because of #58903:
d1a0fa5ed3/compiler/rustc_parse/src/parser/mod.rs (L513-L516)
For `precise_capturing` feature I implemented, we do end up calling `expected_one_of`:
d1a0fa5ed3/compiler/rustc_parse/src/parser/ty.rs (L712-L714)
This leads the compiler to fatal *before* having emitted the first error, leading to absolutely no useful information for the user about what happened in the parser.
This PR makes it so that we stop doing that.
Fixes#124195
Dellvmize some intrinsics (use `u32` instead of `Self` in some integer intrinsics)
This implements https://github.com/rust-lang/compiler-team/issues/693 minus what was implemented in #123226.
Note: I decided to _not_ change `shl`/... builder methods, as it just doesn't seem worth it.
r? ``@scottmcm``
Rollup of 7 pull requests
Successful merges:
- #120929 (Wrap dyn type with parentheses in suggestion)
- #122591 (Suggest using type args directly instead of equality constraint)
- #122598 (deref patterns: lower deref patterns to MIR)
- #123048 (alloc::Layout: explicitly document size invariant on the type level)
- #123993 (Do `check_coroutine_obligations` once per typeck root)
- #124218 (Allow nesting subdiagnostics in #[derive(Subdiagnostic)])
- #124285 (Mark ``@RUSTC_BUILTIN`` search path usage as unstable)
r? `@ghost`
`@rustbot` modify labels: rollup
Do `check_coroutine_obligations` once per typeck root
We only need to do `check_coroutine_obligations` once per typeck root, especially since the new solver can't really (easily) associate which obligations correspond to which coroutines.
This requires us to move the checks for sized coroutine fields into `mir_coroutine_witnesses`, but that's fine imo.
r? lcnr
deref patterns: lower deref patterns to MIR
This lowers deref patterns to MIR. This is a bit tricky because this is the first kind of pattern that requires storing a value in a temporary. Thanks to https://github.com/rust-lang/rust/pull/123324 false edges are no longer a problem.
The thing I'm not confident about is the handling of fake borrows. This PR ignores any fake borrows inside a deref pattern. We are guaranteed to at least fake borrow the place of the first pointer value, which could be enough, but I'm not certain.
Suggest using type args directly instead of equality constraint
When type arguments are written erroneously using an equality constraint we suggest specifying them directly without the equality constraint.
Fixes#122162
Changes the diagnostic in the issue from:
```rust
error[E0229]: associated type bindings are not allowed here
9 | impl std::cmp::PartialEq<Rhs = T> for S {
| ^^^^^^^ associated type not allowed here
|
```
to
```rust
error[E0229]: associated type bindings are not allowed here
9 | impl std::cmp::PartialEq<Rhs = T> for S {
| ^^^^^^^ associated type not allowed here
|
help: to use `T` as a generic argument specify it directly
|
| impl std::cmp::PartialEq<T> for S {
| ~
```
Use fulfillment in method probe, not evaluation
This PR reworks method probing to use fulfillment instead of a `for`-loop of `evaluate_predicate` calls, and moves normalization from method candidate assembly into the `consider_probe`, where it's applied to *all* candidates. This last part coincidentally fixes https://github.com/rust-lang/rust/issues/121643#issuecomment-1975371248.
Regarding *why* this large rewrite is done: In general, it's an anti-pattern to do `for o in obligations { evaluate(o); }` because it's not compatible with the way that the new solver emits alias-relate obligations which constrain variables that may show up in other predicates.
r? lcnr
Disallow ambiguous attributes on expressions
This implements the suggestion in [#15701](https://github.com/rust-lang/rust/issues/15701#issuecomment-2033124217) to disallow ambiguous outer attributes on expressions. This should resolve one of the concerns blocking the stabilization of `stmt_expr_attributes`.
weak lang items are not allowed to be #[track_caller]
For instance the panic handler will be called via this import
```rust
extern "Rust" {
#[lang = "panic_impl"]
fn panic_impl(pi: &PanicInfo<'_>) -> !;
}
```
A `#[track_caller]` would add an extra argument and thus make this the wrong signature.
The 2nd commit is a consistency rename; based on the docs [here](https://doc.rust-lang.org/unstable-book/language-features/lang-items.html) and [here](https://rustc-dev-guide.rust-lang.org/lang-items.html) I figured "lang item" is more widely used. (In the compiler output, "lang item" and "language item" seem to be pretty even.)
panic_str only exists for the migration to 2021 panic macros
The only caller is `expect_failed`, which is already a cold inline(never) function, so inlining into that function should be fine. (And indeed `panic_str` was `#[inline]` anyway.)
The existence of panic_str risks someone calling it when they should call `panic` instead, and I can't see a reason why this footgun should exist.
I also extended the comment in `panic` to explain why it needs a `'static` string -- I know I've wondered about this in the past and it took me quite a while to understand.
