error[E0282]: type annotations needed --> $DIR/issue-23041.rs:6:7 | LL | b.downcast_ref::_>(); | ^^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the method `downcast_ref` | help: consider specifying the generic argument | LL | b.downcast_ref:: _>(); | ~~~~~~~~~~~~~~ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0282`.