error[E0214]: parenthesized type parameters may only be used with a `Fn` trait --> $DIR/unboxed-closure-sugar-used-on-struct-3.rs:14:13 | LL | let b = Bar::(isize, usize)::new(); // OK too (for the parser) | ^^^^^^^^^^^^^^^^^^^ only `Fn` traits may use parentheses | help: use angle brackets instead | LL | let b = Bar::::new(); // OK too (for the parser) | ~ ~ error: aborting due to previous error For more information about this error, try `rustc --explain E0214`.