src/test/ui/type-alias-impl-trait/closure_wf_outlives.rs

   1 // If the hidden type is a closure, we require the "outlives" bounds that appear on the
   2 // defining site to also appear on the opaque type.
   3 //
   4 // It's not clear if this is the desired behavior but at least
   5 // it's consistent and has no back-compat risk.
   6
   7 // check-fail
   8
   9 #![feature(type_alias_impl_trait)]
  10 #![allow(dead_code)]
  11
  12 // requires `'a: 'b` bound
  13 mod test1 {
  14     type Opaque<'a, 'b> = impl Sized + 'a + 'b;
  15     //~^ ERROR lifetime bound not satisfied
  16
  17     fn define<'a, 'b>() -> Opaque<'a, 'b>
  18     where
  19         'a: 'b,
  20     {
  21         || {}
  22     }
  23 }
  24
  25 // Same as the above but through indirection `'x`
  26 mod test2 {
  27     type Opaque<'a, 'b> = impl Sized + 'a + 'b;
  28     //~^ ERROR cannot infer an appropriate lifetime
  29
  30     fn define<'a, 'b, 'x>() -> Opaque<'a, 'b>
  31     where
  32         'a: 'x,
  33         'x: 'b,
  34     {
  35         || {}
  36     }
  37 }
  38
  39 // fixed version of the above
  40 mod test2_fixed {
  41     type Opaque<'a: 'b, 'b> = impl Sized + 'a + 'b;
  42
  43     fn define<'a, 'b, 'x>() -> Opaque<'a, 'b>
  44     where
  45         'a: 'x,
  46         'x: 'b,
  47     {
  48         || {}
  49     }
  50 }
  51
  52 // requires `T: 'static`
  53 mod test3 {
  54     type Opaque<T> = impl Sized;
  55     //~^ ERROR the parameter type `T` may not live long enough
  56
  57     fn define<T>() -> Opaque<T>
  58     where
  59         T: 'static,
  60     {
  61         || {}
  62     }
  63 }
  64
  65 fn main() {}