`obligations_for_self_ty`: use `ProofTreeVisitor` for nested goals
As always, dealing with proof trees continues to be a hacked together mess. After this PR and #124380 the only remaining blocker for core is https://github.com/rust-lang/trait-system-refactor-initiative/issues/90. There is also a `ProofTreeVisitor` issue causing an ICE when compiling `alloc` which I will handle in a separate PR. This issue likely affects coherence diagnostics more generally.
The core idea is to extend the proof tree visitor to support visiting nested candidates without using a `probe`. We then simply recurse into nested candidates if they are the only potentially applicable candidate for a given goal and check whether the self type matches the expected one.
For that to work, we need to improve `CanonicalState` to also handle unconstrained inference variables created inside of the trait solver. This is done by extending the `var_values` of `CanoncalState` with each fresh inference variables. Furthermore, we also store the state of all inference variables at the end of each probe. When recursing into `InspectCandidates` we then unify the values of all these states.
r? `@compiler-errors`
uses a `ProofTreeVisitor` to look into nested
goals when looking at the pending obligations
during hir typeck. Used by closure signature
inference, coercion, and for async functions.
`-Z debug-macros` is "stabilized" by enabling it by default and removing.
`-Z collapse-macro-debuginfo` is stabilized as `-C collapse-macro-debuginfo`.
It now supports all typical boolean values (`parse_opt_bool`) in addition to just yes/no.
Default value of `collapse_debuginfo` was changed from `false` to `external` (i.e. collapsed if external, not collapsed if local).
`#[collapse_debuginfo]` attribute without a value is no longer supported to avoid guessing the default.
Don't ICE when `codegen_select_candidate` returns ambiguity in new solver
Because we merge identical candidates, we may have >1 impl candidate to in `codegen_select_error` but *not* have a trait error.
r? lcnr
Detect borrow error involving sub-slices and suggest `split_at_mut`
```
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.
```
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.
Enforce closure args + return type are WF
I found this out when investigating https://github.com/rust-lang/rust/issues/123461#issuecomment-2040894359. Turns out we don't register WF obligations for closure args and return types, leading to the ICE.
~~I think this is a useful thing to check for, but I'd like to check what the fallout is.~~ crater is complete.
~~Worst case, I think we should enforce this across an edition boundary (and possibly eventually migrate this for all editions) -- this should be super easy to do, since this is a check in HIR wfcheck, so it can be made edition dependent.~~ I believe the regressions are manageable enough to not necessitate edition-specific behavior.
Fixes#123461
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.
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.
