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

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