src/test/ui/inference/cannot-infer-closure-circular.rs

   1 fn main() {
   2     // Below we call the closure with its own return as the argument, unifying
   3     // its inferred input and return types. We want to make sure that the generated
   4     // error handles this gracefully, and in particular doesn't generate an extra
   5     // note about the `?` operator in the closure body, which isn't relevant to
   6     // the inference.
   7     let x = |r| { //~ ERROR type annotations needed for `Result<(), E>`
   8         let v = r?;
   9         Ok(v)
  10     };
  11
  12     let _ = x(x(Ok(())));
  13 }