src/test/ui/regions/regions-infer-bound-from-trait.rs

   1 // Test that we can derive lifetime bounds on type parameters
   2 // from trait inheritance.
   3
   4 trait Static : 'static { }
   5
   6 trait Is<'a> : 'a { }
   7
   8 struct Inv<'a> {
   9     x: Option<&'a mut &'a isize>
  10 }
  11
  12 fn check_bound<'a,A:'a>(x: Inv<'a>, a: A) { }
  13
  14 // In all of these cases, we can derive a bound for A that is longer
  15 // than 'a based on the trait bound of A:
  16
  17 fn foo1<'a,A:Static>(x: Inv<'a>, a: A) {
  18     check_bound(x, a)
  19 }
  20
  21 fn foo2<'a,A:Static>(x: Inv<'static>, a: A) {
  22     check_bound(x, a)
  23 }
  24
  25 fn foo3<'a,A:Is<'a>>(x: Inv<'a>, a: A) {
  26     check_bound(x, a)
  27 }
  28
  29 // In these cases, there is no trait bound, so we cannot derive any
  30 // bound for A and we get an error:
  31
  32 fn bar1<'a,A>(x: Inv<'a>, a: A) {
  33     check_bound(x, a) //~ ERROR parameter type `A` may not live long enough
  34 }
  35
  36 fn bar2<'a,'b,A:Is<'b>>(x: Inv<'a>, y: Inv<'b>, a: A) {
  37     check_bound(x, a) //~ ERROR parameter type `A` may not live long enough
  38 }
  39
  40 fn main() { }