src/test/ui/associated-types/defaults-cyclic-fail-1.rs

   1 #![feature(associated_type_defaults)]
   2
   3 // Having a cycle in assoc. type defaults is okay...
   4 trait Tr {
   5     type A = Self::B;
   6     type B = Self::A;
   7 }
   8
   9 impl Tr for () {}
  10
  11 impl Tr for u8 {
  12     type A = u8;
  13 }
  14
  15 impl Tr for u16 {
  16     type B = ();
  17 }
  18
  19 impl Tr for u32 {
  20     type A = ();
  21     type B = u8;
  22 }
  23
  24 // ...but not in an impl that redefines one of the types.
  25 impl Tr for bool {
  26     type A = Box<Self::B>;
  27     //~^ ERROR overflow evaluating the requirement `<bool as Tr>::B == _`
  28 }
  29 // (the error is shown twice for some reason)
  30
  31 impl Tr for usize {
  32     type B = &'static Self::A;
  33     //~^ ERROR overflow evaluating the requirement `<usize as Tr>::A == _`
  34 }
  35
  36 fn main() {
  37     // We don't check that the types project correctly because the cycle errors stop compilation
  38     // before `main` is type-checked.
  39     // `defaults-cyclic-pass-1.rs` does this.
  40 }