Error code E0687

Note: this error code is no longer emitted by the compiler.

In-band lifetimes cannot be used in fn/Fn syntax.

Erroneous code examples:

#![feature(in_band_lifetimes)] fn foo(x: fn(&'a u32)) {} // error! fn bar(x: &Fn(&'a u32)) {} // error! fn baz(x: fn(&'a u32), y: &'a u32) {} // error! struct Foo<'a> { x: &'a u32 } impl Foo<'a> { fn bar(&self, x: fn(&'a u32)) {} // error! }

Lifetimes used in fn or Fn syntax must be explicitly declared using <...> binders. For example:

#![allow(unused)] fn main() { fn foo<'a>(x: fn(&'a u32)) {} // ok! fn bar<'a>(x: &Fn(&'a u32)) {} // ok! fn baz<'a>(x: fn(&'a u32), y: &'a u32) {} // ok! struct Foo<'a> { x: &'a u32 } impl<'a> Foo<'a> { fn bar(&self, x: fn(&'a u32)) {} // ok! } }