error[E0308]: mismatched types --> $DIR/suggest-calling-rpit-closure.rs:2:5 | LL | fn whatever() -> i32 { | --- expected `i32` because of return type LL | opaque() | ^^^^^^^^ expected `i32`, found opaque type ... LL | fn opaque() -> impl Fn() -> i32 { | ---------------- the found opaque type | = note: expected type `i32` found opaque type `impl Fn() -> i32` help: use parentheses to call this opaque type | LL | opaque()() | ++ error: aborting due to previous error For more information about this error, try `rustc --explain E0308`.