src/test/ui/inference/cannot-infer-closure.stderr

   1 error[E0282]: type annotations needed for the closure `fn((), ()) -> Result<(), _>`
   2   --> $DIR/cannot-infer-closure.rs:3:15
   3    |
   4 LL |         Err(a)?;
   5    |               ^ cannot infer type of error for `?` operator
   6    |
   7    = note: `?` implicitly converts the error value into a type implementing `From<()>`
   8 help: give this closure an explicit return type without `_` placeholders
   9    |
  10 LL |     let x = |a: (), b: ()| -> Result<(), _> {
  11    |                            ^^^^^^^^^^^^^^^^
  12
  13 error: aborting due to previous error
  14
  15 For more information about this error, try `rustc --explain E0282`.