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Add error explanation for E0755
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GuillaumeGomez committed Sep 8, 2020
1 parent 02fe309 commit 69ffed7
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Showing 3 changed files with 30 additions and 1 deletion.
2 changes: 1 addition & 1 deletion compiler/rustc_error_codes/src/error_codes.rs
Expand Up @@ -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"),
Expand Down Expand Up @@ -631,7 +632,6 @@ E0773: include_str!("./error_codes/E0773.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 {}`.
Expand Down
28 changes: 28 additions & 0 deletions compiler/rustc_error_codes/src/error_codes/E0755.md
@@ -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
1 change: 1 addition & 0 deletions src/test/ui/ffi_pure.stderr
Expand Up @@ -6,3 +6,4 @@ LL | #[ffi_pure]

error: aborting due to previous error

For more information about this error, try `rustc --explain E0755`.

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