src/test/ui/specialization/issue-39448.rs

   1 #![feature(specialization)]
   2
   3 // Regression test for a specialization-related ICE (#39448).
   4
   5 trait A: Sized {
   6     fn foo(self, _: Self) -> Self {
   7         self
   8     }
   9 }
  10
  11 impl A for u8 {}
  12 impl A for u16 {}
  13
  14 impl FromA<u8> for u16 {
  15     fn from(x: u8) -> u16 {
  16         x as u16
  17     }
  18 }
  19
  20 trait FromA<T> {
  21     fn from(T) -> Self;
  22 }
  23
  24 impl<T: A, U: A + FromA<T>> FromA<T> for U {
  25     default fn from(x: T) -> Self {
  26         ToA::to(x)
  27     }
  28 }
  29
  30 trait ToA<T> {
  31     fn to(self) -> T;
  32 }
  33
  34 impl<T, U> ToA<U> for T
  35 where
  36     U: FromA<T>,
  37 {
  38     fn to(self) -> U {
  39         U::from(self)
  40     }
  41 }
  42
  43 #[allow(dead_code)]
  44 fn foo<T: A, U: A>(x: T, y: U) -> U {
  45     x.foo(y.to()).to() //~ ERROR overflow evaluating the requirement
  46 }
  47
  48 fn main() {
  49     let z = foo(8u8, 1u16);
  50 }