Rollup merge of #76439 - GuillaumeGomez:add-error-explanation-e0755, r=pickfire,jyn514

Add error explanation for E0755

r? @pickfire
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Ralf Jung 2020-09-21 15:30:34 +02:00 committed by GitHub
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3 changed files with 30 additions and 1 deletions

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@ -440,6 +440,7 @@ E0751: include_str!("./error_codes/E0751.md"),
E0752: include_str!("./error_codes/E0752.md"),
E0753: include_str!("./error_codes/E0753.md"),
E0754: include_str!("./error_codes/E0754.md"),
E0755: include_str!("./error_codes/E0755.md"),
E0758: include_str!("./error_codes/E0758.md"),
E0759: include_str!("./error_codes/E0759.md"),
E0760: include_str!("./error_codes/E0760.md"),
@ -632,7 +633,6 @@ E0774: include_str!("./error_codes/E0774.md"),
E0722, // Malformed `#[optimize]` attribute
E0726, // non-explicit (not `'_`) elided lifetime in unsupported position
// E0738, // Removed; errored on `#[track_caller] fn`s in `extern "Rust" { ... }`.
E0755, // `#[ffi_pure]` is only allowed on foreign functions
E0756, // `#[ffi_const]` is only allowed on foreign functions
E0757, // `#[ffi_const]` functions cannot be `#[ffi_pure]`
E0772, // `'static' obligation coming from `impl dyn Trait {}` or `impl Foo for dyn Bar {}`.

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@ -0,0 +1,28 @@
The `ffi_pure` attribute was used on a non-foreign function.
Erroneous code example:
```compile_fail,E0755
#![feature(ffi_pure)]
#[ffi_pure] // error!
pub fn foo() {}
# fn main() {}
```
The `ffi_pure` attribute can only be used on foreign functions which do not have
side effects or infinite loops:
```
#![feature(ffi_pure)]
extern "C" {
#[ffi_pure] // ok!
pub fn strlen(s: *const i8) -> isize;
}
# fn main() {}
```
You can find more information about it in the [unstable Rust Book].
[unstable Rust Book]: https://doc.rust-lang.org/unstable-book/language-features/ffi-pure.html

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@ -6,3 +6,4 @@ LL | #[ffi_pure]
error: aborting due to previous error
For more information about this error, try `rustc --explain E0755`.