Tweak some structured suggestions to be more verbose and accurate
Addressing some issues I found while working on #127282.
```
error: this URL is not a hyperlink
--> $DIR/auxiliary/include-str-bare-urls.md:1:11
|
LL | HEADS UP! https://example.com MUST SHOW UP IN THE STDERR FILE!
| ^^^^^^^^^^^^^^^^^^^
|
= note: bare URLs are not automatically turned into clickable links
note: the lint level is defined here
--> $DIR/include-str-bare-urls.rs:14:9
|
LL | #![deny(rustdoc::bare_urls)]
| ^^^^^^^^^^^^^^^^^^
help: use an automatic link instead
|
LL | HEADS UP! <https://example.com> MUST SHOW UP IN THE STDERR FILE!
| + +
```
```
error[E0384]: cannot assign twice to immutable variable `v`
--> $DIR/assign-imm-local-twice.rs:7:5
|
LL | v = 1;
| ----- first assignment to `v`
LL | println!("v={}", v);
LL | v = 2;
| ^^^^^ cannot assign twice to immutable variable
|
help: consider making this binding mutable
|
LL | let mut v: isize;
| +++
```
```
error[E0393]: the type parameter `Rhs` must be explicitly specified
--> $DIR/issue-22560.rs:9:23
|
LL | trait Sub<Rhs=Self> {
| ------------------- type parameter `Rhs` must be specified for this
...
LL | type Test = dyn Add + Sub;
| ^^^
|
= note: because of the default `Self` reference, type parameters must be specified on object types
help: set the type parameter to the desired type
|
LL | type Test = dyn Add + Sub<Rhs>;
| +++++
```
```
error[E0596]: cannot borrow `v` as mutable, as it is not declared as mutable
--> $DIR/issue-33819.rs:4:34
|
LL | Some(ref v) => { let a = &mut v; },
| ^^^^^^ cannot borrow as mutable
|
help: try removing `&mut` here
|
LL - Some(ref v) => { let a = &mut v; },
LL + Some(ref v) => { let a = v; },
|
```
```
help: remove the invocation before committing it to a version control system
|
LL - dbg!();
|
```
```
error[E0308]: mismatched types
--> $DIR/issue-39974.rs:1:21
|
LL | const LENGTH: f64 = 2;
| ^ expected `f64`, found integer
|
help: use a float literal
|
LL | const LENGTH: f64 = 2.0;
| ++
```
```
error[E0529]: expected an array or slice, found `Vec<i32>`
--> $DIR/match-ergonomics.rs:8:9
|
LL | [&v] => {},
| ^^^^ pattern cannot match with input type `Vec<i32>`
|
help: consider slicing here
|
LL | match x[..] {
| ++++
```
```
error[E0609]: no field `0` on type `[u32; 1]`
--> $DIR/parenthesized-deref-suggestion.rs:10:21
|
LL | (x as [u32; 1]).0;
| ^ unknown field
|
help: instead of using tuple indexing, use array indexing
|
LL | (x as [u32; 1])[0];
| ~ +
```
`E0229`: Suggest Moving Type Constraints to Type Parameter Declaration
Fixes#113073
This PR suggests `impl<T: Bound> Trait<T> for Foo` when finding `impl Trait<T: Bound> for Foo`. Tangentially, it also improves a handful of other error messages.
It accomplishes this in two steps:
1. Check if constrained arguments and parameter names appear in the same order and delay emitting "incorrect number of generic arguments" error because it can be confusing for the programmer to see `0 generic arguments provided` when there are `n` constrained generic arguments.
2. Inside `E0229`, suggest declaring the type parameter right after the `impl` keyword by finding the relevant impl block's span for type parameter declaration. This also handles lifetime declarations correctly.
Also, the multi part suggestion doesn't use the fluent error mechanism because translating all the errors to fluent style feels outside the scope of this PR. I will handle it in a separate PR if this gets approved.
Account for existing bindings when suggesting `pin!()`
When we encounter a situation where we'd suggest `pin!()`, we now account for that expression existing as part of an assignment and provide an appropriate suggestion:
```
error[E0599]: no method named `poll` found for type parameter `F` in the current scope
--> $DIR/pin-needed-to-poll-3.rs:19:28
|
LL | impl<F> Future for FutureWrapper<F>
| - method `poll` not found for this type parameter
...
LL | let res = self.fut.poll(cx);
| ^^^^ method not found in `F`
|
help: consider pinning the expression
|
LL ~ let mut pinned = std::pin::pin!(self.fut);
LL ~ let res = pinned.as_mut().poll(cx);
|
```
Fix#125661.
Use parenthetical notation for `Fn` traits
Always use the `Fn(T) -> R` format when printing closure traits instead of `Fn<(T,), Output = R>`.
Address #67100:
```
error[E0277]: expected a `Fn()` closure, found `F`
--> file.rs:6:13
|
6 | call_fn(f)
| ------- ^ expected an `Fn()` closure, found `F`
| |
| required by a bound introduced by this call
|
= note: wrap the `F` in a closure with no arguments: `|| { /* code */ }`
note: required by a bound in `call_fn`
--> file.rs:1:15
|
1 | fn call_fn<F: Fn() -> ()>(f: &F) {
| ^^^^^^^^^^ required by this bound in `call_fn`
help: consider further restricting this bound
|
5 | fn call_any<F: std::any::Any + Fn()>(f: &F) {
| ++++++
```
Implement `needs_async_drop` in rustc and optimize async drop glue
This PR expands on #121801 and implements `Ty::needs_async_drop` which works almost exactly the same as `Ty::needs_drop`, which is needed for #123948.
Also made compiler's async drop code to look more like compiler's regular drop code, which enabled me to write an optimization where types which do not use `AsyncDrop` can simply forward async drop glue to `drop_in_place`. This made size of the async block from the [async_drop test](67980dd6fb/tests/ui/async-await/async-drop.rs) to decrease by 12%.
Always use the `Fn(T) -> R` format when printing closure traits instead of `Fn<(T,), Output = R>`.
Fix#67100:
```
error[E0277]: expected a `Fn()` closure, found `F`
--> file.rs:6:13
|
6 | call_fn(f)
| ------- ^ expected an `Fn()` closure, found `F`
| |
| required by a bound introduced by this call
|
= note: wrap the `F` in a closure with no arguments: `|| { /* code */ }`
note: required by a bound in `call_fn`
--> file.rs:1:15
|
1 | fn call_fn<F: Fn() -> ()>(f: &F) {
| ^^^^^^^^^^ required by this bound in `call_fn`
help: consider further restricting this bound
|
5 | fn call_any<F: std::any::Any + Fn()>(f: &F) {
| ++++++
```
When we encounter a situation where we'd suggest `pin!()`, we now account for that expression exising as part of an assignment and provide an appropriate suggestion:
```
error[E0599]: no method named `poll` found for type parameter `F` in the current scope
--> $DIR/pin-needed-to-poll-3.rs:19:28
|
LL | impl<F> Future for FutureWrapper<F>
| - method `poll` not found for this type parameter
...
LL | let res = self.fut.poll(cx);
| ^^^^ method not found in `F`
|
help: consider pinning the expression
|
LL ~ let mut pinned = std::pin::pin!(self.fut);
LL ~ let res = pinned.as_mut().poll(cx);
|
```
Fix#125661.
The following suggestion is incorrect, as it doesn't account for the binding:
```
error[E0599]: no method named `poll` found for type parameter `F` in the current scope
--> $DIR/pin-needed-to-poll-3.rs:19:28
|
LL | impl<F> Future for FutureWrapper<F>
| - method `poll` not found for this type parameter
...
LL | let res = self.fut.poll(cx);
| ^^^^ method not found in `F`
|
help: consider pinning the expression
|
LL ~ let res = let mut pinned = std::pin::pin!(self.fut);
LL ~ pinned.as_mut().poll(cx);
|
```
Rollup of 7 pull requests
Successful merges:
- #125043 (reference type safety invariant docs: clarification)
- #125306 (Force the inner coroutine of an async closure to `move` if the outer closure is `move` and `FnOnce`)
- #125355 (Use Backtrace::force_capture instead of Backtrace::capture in rustc_log)
- #125382 (rustdoc: rename `issue-\d+.rs` tests to have meaningful names (part 7))
- #125391 (Minor serialize/span tweaks)
- #125395 (Remove unnecessary `.md` from the documentation sidebar)
- #125399 (Stop using `to_hir_binop` in codegen)
r? `@ghost`
`@rustbot` modify labels: rollup
Force the inner coroutine of an async closure to `move` if the outer closure is `move` and `FnOnce`
See the detailed comment in `upvar.rs`.
Fixes#124867.
Fixes#124487.
r? oli-obk
An async closure may implement `FnMut`/`Fn` if it has no self-borrows
There's no reason that async closures may not implement `FnMut` or `Fn` if they don't actually borrow anything with the closure's env lifetime. Specifically, #123660 made it so that we don't always need to borrow captures from the closure's env.
See the doc comment on `should_reborrow_from_env_of_parent_coroutine_closure`:
c00957a3e2/compiler/rustc_hir_typeck/src/upvar.rs (L1777-L1823)
If there are no such borrows, then we are free to implement `FnMut` and `Fn` as permitted by our closure's inferred `ClosureKind`.
As far as I can tell, this change makes `async || {}` work in precisely the set of places they used to work before #120361.
Fixes#125247.
r? oli-obk
Deny gen keyword in `edition_2024_compat` lints
Splits the `keyword_idents` lint into two -- `keyword_idents_2018` and `keyword_idents_2024` -- since each corresponds to a future-compat warning in a different edition. Group these together into a new `keyword_idents` lint group, and add the latter to the `rust_2024_compatibility` so that `gen` is ready for the 2024 edition.
cc `@traviscross` `@ehuss`
Stop using `HirId` for fn-like parents since closures are not `OwnerNode`s
This is a minimal fix for #123273.
I'm overall pretty disappointed w/ the state of this code; although it's "just diagnostics", it still should be maintainable and understandable and neither of those are true. I believe this code really needs some major overhauling before anything more should be added to it, because there are subtle invariants that are being exercised and subsequently broken all over the place, and I don't think we should just paper over them (e.g.) by delaying bugs or things like that. I wouldn't be surprised if fixing up this code would also yield better diagnostics.
Make the computation of `coroutine_captures_by_ref_ty` more sophisticated
Currently, we treat all the by-(mut/)ref borrows of a coroutine-closure as having a "closure env" borrowed lifetime.
When we have the given code:
```rust
let x: &'a i32 = ...;
let c = async || {
let _x = *x;
};
```
Then when we call:
```rust
c()
// which, because `AsyncFn` takes a `&self`, we insert an autoref:
(&c /* &'env {coroutine-closure} */)()
```
We will return a future whose captures contain `&'env i32` instead of `&'a i32`, which is way more restrictive than necessary. We should be able to drop `c` while the future is alive since it's not actually borrowing any data *originating from within* the closure's captures, but since the capture has that `'env` lifetime, this is not possible.
This wouldn't be true, for example, if the closure captured `i32` instead of `&'a i32`, because the `'env` lifetime is actually *necessary* since the data (`i32`) is owned by the closure.
This PR identifies two criteria where we *need* to take the borrow with the closure env lifetime:
1. If the closure borrows data from inside the closure's captures. This is not true if the parent capture is by-ref, OR if the parent capture is by-move and the child capture begins with a deref projection. This is the example described above.
2. If we're dealing with mutable references, since we cannot reborrow `&'env mut &'a mut i32` into `&'a mut i32`, *only* `&'env mut i32`.
See the documentation on `should_reborrow_from_env_of_parent_coroutine_closure` for more info.
**important:** As disclaimer states on that function, luckily, if this heuristic is not correct, then the program is not unsound, since we still borrowck and validate the choices made from this function -- the only side-effect is that the user may receive unnecessary borrowck errors.
Fixes#123241
