1error[E0214]: parenthesized type parameters may only be used with a `Fn` trait 2 --> $DIR/unboxed-closure-sugar-used-on-struct.rs:7:15 3 | 4LL | fn foo(b: Box<Bar()>) { 5 | ^^^^^ only `Fn` traits may use parentheses 6 7error[E0107]: this struct takes 1 generic argument but 0 generic arguments were supplied 8 --> $DIR/unboxed-closure-sugar-used-on-struct.rs:7:15 9 | 10LL | fn foo(b: Box<Bar()>) { 11 | ^^^ expected 1 generic argument 12 | 13note: struct defined here, with 1 generic parameter: `A` 14 --> $DIR/unboxed-closure-sugar-used-on-struct.rs:3:8 15 | 16LL | struct Bar<A> { 17 | ^^^ - 18help: add missing generic argument 19 | 20LL | fn foo(b: Box<Bar(A)>) { 21 | + 22 23error: aborting due to 2 previous errors 24 25Some errors have detailed explanations: E0107, E0214. 26For more information about an error, try `rustc --explain E0107`. 27