error[E0282]: type annotations needed --> $DIR/issue-99565.rs:6:5 | LL | foo(|| {}); | ^^^ cannot infer type of the type parameter `T` declared on the function `foo` | help: consider specifying the generic arguments | LL | foo::(|| {}); | ++++++++ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0282`.