compiler/rustc_error_codes/src/error_codes/E0687.md

   1 #### Note: this error code is no longer emitted by the compiler.
   2
   3 In-band lifetimes cannot be used in `fn`/`Fn` syntax.
   4
   5 Erroneous code examples:
   6
   7 ```ignore (feature got removed)
   8 #![feature(in_band_lifetimes)]
   9
  10 fn foo(x: fn(&'a u32)) {} // error!
  11
  12 fn bar(x: &Fn(&'a u32)) {} // error!
  13
  14 fn baz(x: fn(&'a u32), y: &'a u32) {} // error!
  15
  16 struct Foo<'a> { x: &'a u32 }
  17
  18 impl Foo<'a> {
  19     fn bar(&self, x: fn(&'a u32)) {} // error!
  20 }
  21 ```
  22
  23 Lifetimes used in `fn` or `Fn` syntax must be explicitly
  24 declared using `<...>` binders. For example:
  25
  26 ```
  27 fn foo<'a>(x: fn(&'a u32)) {} // ok!
  28
  29 fn bar<'a>(x: &Fn(&'a u32)) {} // ok!
  30
  31 fn baz<'a>(x: fn(&'a u32), y: &'a u32) {} // ok!
  32
  33 struct Foo<'a> { x: &'a u32 }
  34
  35 impl<'a> Foo<'a> {
  36     fn bar(&self, x: fn(&'a u32)) {} // ok!
  37 }
  38 ```