tests/ui/never_type/fallback-closure-wrap.rs

   1 // This is a minified example from Crater breakage observed when attempting to
   2 // stabilize never type, nstoddard/webgl-gui @ 22f0169f.
   3 //
   4 // This particular test case currently fails as the inference to `()` rather
   5 // than `!` happens as a result of an `as` cast, which is not currently tracked.
   6 // Crater did not find many cases of this occurring, but it is included for
   7 // awareness.
   8 //
   9 // revisions: nofallback fallback
  10 //[nofallback] check-pass
  11 //[fallback] check-fail
  12
  13 #![cfg_attr(fallback, feature(never_type_fallback))]
  14
  15 use std::marker::PhantomData;
  16
  17 fn main() {
  18     let error = Closure::wrap(Box::new(move || {
  19         //[fallback]~^ to be a closure that returns `()`, but it returns `!`
  20         panic!("Can't connect to server.");
  21     }) as Box<dyn FnMut()>);
  22 }
  23
  24 struct Closure<T: ?Sized>(PhantomData<T>);
  25
  26 impl<T: ?Sized> Closure<T> {
  27     fn wrap(data: Box<T>) -> Closure<T> {
  28         todo!()
  29     }
  30 }