error: the `Self` constructor can only be used with tuple or unit structs --> $DIR/issue-56835.rs:4:12 | LL | fn bar(Self(foo): Self) {} | ^^^^^^^^^ help: use curly brackets: `Self { /* fields */ }` error[E0164]: expected tuple struct or tuple variant, found self constructor `Self` --> $DIR/issue-56835.rs:4:12 | LL | fn bar(Self(foo): Self) {} | ^^^^^^^^^ not a tuple struct or tuple variant error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0164`.