src/test/ui/issues/issue-50687-ice-on-borrow.rs

   1 // This previously caused an ICE at:
   2 // librustc/traits/structural_impls.rs:180: impossible case reached
   3
   4 #![no_main]
   5
   6 use std::borrow::Borrow;
   7 use std::io;
   8 use std::io::Write;
   9
  10 trait Constraint {}
  11
  12 struct Container<T> {
  13     t: T,
  14 }
  15
  16 struct Borrowed;
  17 struct Owned;
  18
  19 impl<'a, T> Write for &'a Container<T>
  20 where
  21     T: Constraint,
  22     &'a T: Write,
  23 {
  24     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
  25         Ok(buf.len())
  26     }
  27
  28     fn flush(&mut self) -> io::Result<()> {
  29         Ok(())
  30     }
  31 }
  32
  33 impl Borrow<Borrowed> for Owned {
  34     fn borrow(&self) -> &Borrowed {
  35         &Borrowed
  36     }
  37 }
  38
  39 fn func(owned: Owned) {
  40     let _: () = Borrow::borrow(&owned); //~ ERROR mismatched types
  41 }