src/test/ui/issues/issue-23041.stderr

   1 error[E0282]: type annotations needed
   2   --> $DIR/issue-23041.rs:16:22
   3    |
   4 LL |     b.downcast_ref::<fn(_)->_>(); //~ ERROR E0282
   5    |                      ^^^^^^^^ cannot infer type
   6
   7 error: aborting due to previous error
   8
   9 For more information about this error, try `rustc --explain E0282`.