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Rollup merge of #79208 - LeSeulArtichaut:stable-unsafe_op_in_unsafe_fn, r=nikomatsakis

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Stabilize `unsafe_op_in_unsafe_fn` lint

This makes it possible to override the level of the `unsafe_op_in_unsafe_fn`, as proposed in https://github.com/rust-lang/rust/issues/71668#issuecomment-729770896.

Tracking issue: #71668
r? ```@nikomatsakis``` cc ```@SimonSapin``` ```@RalfJung```

# Stabilization report

This is a stabilization report for `#![feature(unsafe_block_in_unsafe_fn)]`.

## Summary

Currently, the body of unsafe functions is an unsafe block, i.e. you can perform unsafe operations inside.

The `unsafe_op_in_unsafe_fn` lint, stabilized here, can be used to change this behavior, so performing unsafe operations in unsafe functions requires an unsafe block.

For now, the lint is allow-by-default, which means that this PR does not change anything without overriding the lint level.

For more information, see [RFC 2585](https://github.com/rust-lang/rfcs/blob/master/text/2585-unsafe-block-in-unsafe-fn.md)

### Example

```rust
// An `unsafe fn` for demonstration purposes.
// Calling this is an unsafe operation.
unsafe fn unsf() {}

// #[allow(unsafe_op_in_unsafe_fn)] by default,
// the behavior of `unsafe fn` is unchanged
unsafe fn allowed() {
    // Here, no `unsafe` block is needed to
    // perform unsafe operations...
    unsf();

    // ...and any `unsafe` block is considered
    // unused and is warned on by the compiler.
    unsafe {
        unsf();
    }
}

#[warn(unsafe_op_in_unsafe_fn)]
unsafe fn warned() {
    // Removing this `unsafe` block will
    // cause the compiler to emit a warning.
    // (Also, no "unused unsafe" warning will be emitted here.)
    unsafe {
        unsf();
    }
}

#[deny(unsafe_op_in_unsafe_fn)]
unsafe fn denied() {
    // Removing this `unsafe` block will
    // cause a compilation error.
    // (Also, no "unused unsafe" warning will be emitted here.)
    unsafe {
        unsf();
    }
}
```
This commit is contained in:
Yuki Okushi 2021-03-10 08:01:25 +09:00 • committed by GitHub
commit c46f948a80
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13 changed files with 26 additions and 74 deletions
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3
compiler/rustc_feature/src/active.rs
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@ -557,9 +557,6 @@ declare_features! (
/// Allows the use of `#[ffi_const]` on foreign functions.
(active, ffi_const, "1.45.0", Some(58328), None),
/// No longer treat an unsafe function as an unsafe block.
(active, unsafe_block_in_unsafe_fn, "1.45.0", Some(71668), None),
/// Allows `extern "avr-interrupt" fn()` and `extern "avr-non-blocking-interrupt" fn()`.
(active, abi_avr_interrupt, "1.45.0", Some(69664), None),