error: where clauses are not allowed before tuple struct bodies --> $DIR/issue-17904.rs:6:15 | LL | struct Foo where T: Copy, (T); | --- ^^^^^^^^^^^^^^ --- the struct body | | | | | unexpected where clause | while parsing this tuple struct | help: move the body before the where clause | LL - struct Foo where T: Copy, (T); LL + struct Foo(T) where T: Copy; | error: aborting due to previous error