Rollup of 5 pull requests
Successful merges:
- #95294 (Document Linux kernel handoff in std::io::copy and std::fs::copy)
- #95443 (Clarify how `src/tools/x` searches for python)
- #95452 (fix since field version for termination stabilization)
- #95460 (Spellchecking compiler code)
- #95461 (Spellchecking some comments)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Lazy type-alias-impl-trait take two
### user visible change 1: RPIT inference from recursive call sites
Lazy TAIT has an insta-stable change. The following snippet now compiles, because opaque types can now have their hidden type set from wherever the opaque type is mentioned.
```rust
fn bar(b: bool) -> impl std::fmt::Debug {
if b {
return 42
}
let x: u32 = bar(false); // this errors on stable
99
}
```
The return type of `bar` stays opaque, you can't do `bar(false) + 42`, you need to actually mention the hidden type.
### user visible change 2: divergence between RPIT and TAIT in return statements
Note that `return` statements and the trailing return expression are special with RPIT (but not TAIT). So
```rust
#![feature(type_alias_impl_trait)]
type Foo = impl std::fmt::Debug;
fn foo(b: bool) -> Foo {
if b {
return vec![42];
}
std::iter::empty().collect() //~ ERROR `Foo` cannot be built from an iterator
}
fn bar(b: bool) -> impl std::fmt::Debug {
if b {
return vec![42]
}
std::iter::empty().collect() // Works, magic (accidentally stabilized, not intended)
}
```
But when we are working with the return value of a recursive call, the behavior of RPIT and TAIT is the same:
```rust
type Foo = impl std::fmt::Debug;
fn foo(b: bool) -> Foo {
if b {
return vec![];
}
let mut x = foo(false);
x = std::iter::empty().collect(); //~ ERROR `Foo` cannot be built from an iterator
vec![]
}
fn bar(b: bool) -> impl std::fmt::Debug {
if b {
return vec![];
}
let mut x = bar(false);
x = std::iter::empty().collect(); //~ ERROR `impl Debug` cannot be built from an iterator
vec![]
}
```
### user visible change 3: TAIT does not merge types across branches
In contrast to RPIT, TAIT does not merge types across branches, so the following does not compile.
```rust
type Foo = impl std::fmt::Debug;
fn foo(b: bool) -> Foo {
if b {
vec![42_i32]
} else {
std::iter::empty().collect()
//~^ ERROR `Foo` cannot be built from an iterator over elements of type `_`
}
}
```
It is easy to support, but we should make an explicit decision to include the additional complexity in the implementation (it's not much, see a721052457cf513487fb4266e3ade65c29b272d2 which needs to be reverted to enable this).
### PR formalities
previous attempt: #92007
This PR also includes #92306 and #93783, as they were reverted along with #92007 in #93893fixes#93411fixes#88236fixes#89312fixes#87340fixes#86800fixes#86719fixes#84073fixes#83919fixes#82139fixes#77987fixes#74282fixes#67830fixes#62742fixes#54895
Suggest wrapping patterns in enum variants
Structured suggestion to wrap a pattern in a single-field enum or struct:
```diff
struct A;
enum B {
A(A),
}
fn main(b: B) {
match b {
- A => {}
+ B::A(A) => {}
}
}
```
Half of #94942, the other half I'm not exactly sure how to fix.
Also includes two drive-by changes (that I am open to splitting out into another PR, but thought they could be rolled up into this one):
- 07776c111f: Makes sure not to suggest wrapping if it doesn't have tuple field constructor (i.e. has named fields)
- 8f2bbb18fd53e5008bb488302dbd354577698ede: Also suggest wrapping expressions in a tuple struct (not just enum variants)
Stabilize Termination and ExitCode
From https://github.com/rust-lang/rust/issues/43301
This PR stabilizes the Termination trait and associated ExitCode type. It also adjusts the ExitCode feature flag to replace the placeholder flag with a more permanent name, as well as splitting off the `to_i32` method behind its own permanently unstable feature flag.
This PR stabilizes the termination trait with the following signature:
```rust
pub trait Termination {
fn report(self) -> ExitCode;
}
```
The existing impls of `Termination` are effectively already stable due to the prior stabilization of `?` in main.
This PR also stabilizes the following APIs on exit code
```rust
#[derive(Clone, Copy, Debug)]
pub struct ExitCode(_);
impl ExitCode {
pub const SUCCESS: ExitCode;
pub const FAILURE: ExitCode;
}
impl From<u8> for ExitCode { /* ... */ }
```
---
All of the previous blockers have been resolved. The main ones that were resolved recently are:
* The trait's name: We decided against changing this since none of the alternatives seemed particularly compelling. Instead we decided to end the bikeshedding and stick with the current name. ([link to the discussion](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Termination.2FExit.20Status.20Stabilization/near/269793887))
* Issues around platform specific representations: We resolved this issue by changing the return type of `report` from `i32` to the opaque type `ExitCode`. That way we can change the underlying representation without affecting the API, letting us offer full support for platform specific exit code APIs in the future.
* Custom exit codes: We resolved this by adding `From<u8> for ExitCode`. We choose to only support u8 initially because it is the least common denominator between the sets of exit codes supported by our current platforms. In the future we anticipate adding platform specific extension traits to ExitCode for constructors from larger or negative numbers, as needed.
Show ignore message in console and json output
- Provide ignore the message in console and JSON output
- Modify the ignore message style in the log file
related: #92714
Show ignore message in console and json output
- Provide ignore the message in console and JSON output
- Modify the ignore message style in the log file
related: #92714
Add suggestion to borrow `Fn` and `FnMut` params/opaque/closures instead of move
I think that Closure/ParamTy/Opaque are all "opaque" enough that it's meaningful to suggest borrowing them instead of moving them at their usage sites when we see a move error. See the attached issue for example.
Is this suggestion too general? I could perhaps use the move site information to limit this to places like fn calls, but I don't know enough about mir borrowck to know if that's an easy change.
Fixes#90828
bootstrap: better error message for no_std docs
Currently if one tries to build std documentation for a no_std target, you get a confusing error message:
`error: The argument '--package [<SPEC>...]' was provided more than once, but cannot be used multiple times`
This is because [`std_cargo`](600ec28483/src/bootstrap/compile.rs (L299-L305)) has a built-in `-p alloc` argument that conflicts with the `cargo rustdoc` command used in the Std doc step.
This just adds a better error message in this scenario. It may be possible to fix this correctly, but that would likely be a bit more of an invasive change that I don't have time for right now.
Fix yet another Box<T, A> ICE
Fixes#95036.
This widens the special case from #94414 to make sure that boxes with a custom allocator are never directly dereferenced.
parallel_compiler: hide dependencies behind feature
Separate dependencies for `parallel_compiler` feature, so they will not be compiled if feature not selected, reducing number of compiled crates from 238 to 224.
