diff options
Diffstat (limited to 'compiler/rustc_error_codes/src/error_codes/E0581.md')
-rw-r--r-- | compiler/rustc_error_codes/src/error_codes/E0581.md | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/compiler/rustc_error_codes/src/error_codes/E0581.md b/compiler/rustc_error_codes/src/error_codes/E0581.md new file mode 100644 index 000000000..02468dd94 --- /dev/null +++ b/compiler/rustc_error_codes/src/error_codes/E0581.md @@ -0,0 +1,31 @@ +In a `fn` type, a lifetime appears only in the return type +and not in the arguments types. + +Erroneous code example: + +```compile_fail,E0581 +fn main() { + // Here, `'a` appears only in the return type: + let x: for<'a> fn() -> &'a i32; +} +``` + +The problem here is that the lifetime isn't constrained by any of the arguments, +making it impossible to determine how long it's supposed to live. + +To fix this issue, either use the lifetime in the arguments, or use the +`'static` lifetime. Example: + +``` +fn main() { + // Here, `'a` appears only in the return type: + let x: for<'a> fn(&'a i32) -> &'a i32; + let y: fn() -> &'static i32; +} +``` + +Note: The examples above used to be (erroneously) accepted by the +compiler, but this was since corrected. See [issue #33685] for more +details. + +[issue #33685]: https://github.com/rust-lang/rust/issues/33685 |