Rollup of 4 pull requests #94706
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Rollup of 4 pull requests #94706
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It seems the removal of these in 1c07096 was unintended; readding them fixes the build. fixes rust-lang#93349
…align line numbers to the right
libunwind: readd link attrs to _Unwind_Backtrace It seems the removal of these in 1c07096 was unintended; readding them fixes the build. fixes rust-lang#93349 r? `@alexcrichton`
…r=wesleywiser
Stabilize const_fn_fn_ptr_basics, const_fn_trait_bound, and const_impl_trait
# Stabilization Report
This PR serves as a request for stabilization for three const evaluation features:
1. `const_fn_fn_ptr_basics`
2. `const_fn_trait_bound`
3. `const_impl_trait`
These are being stabilized together because they are relatively minor and related updates to existing functionality.
## `const_fn_fn_ptr_basics`
Allows creating, passing, and casting function pointers in a `const fn`.
The following is an example of what is now allowed:
```rust
const fn get_function() -> fn() {
fn foo() {
println!("Hello, World!");
}
foo
}
```
Casts between function pointer types are allowed, as well as transmuting from integers:
```rust
const fn get_function() -> fn() {
unsafe {
std::mem::transmute(0x1234usize)
}
}
```
However, casting from a function pointer to an integer is not allowed:
```rust
const fn fn_to_usize(f: fn()) -> usize {
f as usize //~ pointers cannot be cast to integers during const eval
}
```
Calling function pointers is also not allowed.
```rust
const fn call_fn_ptr(f: fn()) {
f() //~ function pointers are not allowed in const fn
}
```
### Test Coverage
The following tests include code that exercises this feature:
- `src/test/ui/consts/issue-37550.rs`
- `src/test/ui/consts/issue-46553.rs`
- `src/test/ui/consts/issue-56164.rs`
- `src/test/ui/consts/min_const_fn/allow_const_fn_ptr_run_pass.rs`
- `src/test/ui/consts/min_const_fn/cast_fn.rs`
- `src/test/ui/consts/min_const_fn/cmp_fn_pointers.rs`
## `const_fn_trait_bound`
Allows trait bounds in `const fn`. Additionally, this feature allows creating and passing `dyn Trait` objects.
Examples such as the following are allowed by this feature:
```rust
const fn do_thing<T: Foo>(_x: &T) {
// ...
}
```
Previously only `Sized` was allowed as a trait bound.
There is no way to call methods from the trait because trait methods cannot currently be marked as const. Allowing trait bounds in const functions does allow the const function to use the trait's associated types and constants.
This feature also allowes `dyn Trait` types. These work equivalently to non-const code. Similar to other pointers in const code, the value of a `dyn Trait` pointer cannot be observed.
Note that due to rust-lang#90912, it was already possible to do the example above as follows:
```rust
const fn do_thing<T>(_x: &T) where (T,): Foo {
// ...
}
```
### Test Coverage
The following tests include code that exercises `const_fn_trait_bound`:
- `src/test/ui/consts/const-fn.rs`
- `src/test/ui/consts/issue-88071.rs`
- `src/test/ui/consts/min_const_fn/min_const_fn.rs`
- `src/test/ui/consts/min_const_fn/min_const_fn_dyn.rs`
- `src/test/ui/nll/issue-55825-const-fn.rs`
- Many of the tests in `src/test/ui/rfc-2632-const-trait-impl/` also exercise this feature.
## `const_impl_trait`
Allows argument and return position `impl Trait` in a `const fn`, such as in the following example:
```rust
const fn do_thing(x: impl Foo) -> impl Foo {
x
}
```
Similar to generic parameters and function pointers, this allows the creation of such opaque types, but not doing anything with them beyond accessing associated types and constants.
### Test Coverage
The following tests exercise this feature:
- `src/test/ui/type-alias-impl-trait/issue-53096.rs`
- `src/test/ui/type-alias-impl-trait/issue-53678-generator-and-const-fn.rs`
## Documentation
These features are documented along with the other const evaluation features in the Rust Reference at https://doc.rust-lang.org/stable/reference/const_eval.html.
There is a PR that updates this documentation to reflect the capabilities enabled by these features at rust-lang/reference#1166.
Tracking issues: rust-lang#57563, rust-lang#63997, rust-lang#93706
…ight, r=notriddle Remove whitespaces and use CSS to align line numbers to the right instead Instead of generating whitespaces to create padding, we simply use the CSS rule: `text-align: right`. Nice side-effect: it reduces the generated HTML size from **75.004** to **74.828** (MegaBytes) on the std source pages (it's not much but it's always a nice plus 😆 ). There are no changes in the generated UI. r? `@notriddle`
…otriddle rustdoc: Update minifier version This new version includes a fix for the CSS minifier which was badly handling inline media queries like ``@import` 'i';`. r? `@notriddle`
rustbot
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@bors r+ rollup=never p=4 |
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📌 Commit b3261f8 has been approved by |
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☀️ Test successful - checks-actions |
This was referenced Mar 7, 2022
|
Finished benchmarking commit (03918ba): comparison url. Summary: This benchmark run did not return any relevant results. If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf. @rustbot label: -perf-regression |
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Mar 14, 2022
…askrgr Rollup of 4 pull requests Successful merges: - rust-lang#93350 (libunwind: readd link attrs to _Unwind_Backtrace) - rust-lang#93827 (Stabilize const_fn_fn_ptr_basics, const_fn_trait_bound, and const_impl_trait) - rust-lang#94696 (Remove whitespaces and use CSS to align line numbers to the right instead) - rust-lang#94700 (rustdoc: Update minifier version) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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