diff --git a/compiler/rustc_error_codes/src/error_codes/E0582.md b/compiler/rustc_error_codes/src/error_codes/E0582.md index e50cc60ea3302..b2cdb509c95c0 100644 --- a/compiler/rustc_error_codes/src/error_codes/E0582.md +++ b/compiler/rustc_error_codes/src/error_codes/E0582.md @@ -27,6 +27,40 @@ fn bar(t: F, u: G) fn main() { } ``` +This error also includes the use of associated types with lifetime parameters. +```compile_fail,E0582 +trait Foo { + type Assoc<'a>; +} + +struct Bar +where + X: Foo, + F: for<'a> Fn(X::Assoc<'a>) -> &'a i32 +{ + x: X, + f: F +} +``` +The latter scenario encounters this error because `Foo::Assoc<'a>` could be +implemented by a type that does not use the `'a` parameter, so there is no +guarentee that `X::Assoc<'a>` actually uses `'a`. + +To fix this we can pass a dummy parameter: +``` +# trait Foo { +# type Assoc<'a>; +# } +struct Bar +where + X: Foo, + F: for<'a> Fn(X::Assoc<'a>, /* dummy */ &'a ()) -> &'a i32 +{ + x: X, + f: F +} +``` + Note: The examples above used to be (erroneously) accepted by the compiler, but this was since corrected. See [issue #33685] for more details.