error[E0308]: mismatched types --> $DIR/issue-7061.rs:4:46 | LL | fn foo(&'a mut self) -> Box { self } | -------------- ^^^^ expected struct `Box`, found `&mut BarStruct` | | | expected `Box` because of return type | = note: expected struct `Box` found mutable reference `&'a mut BarStruct` error: aborting due to previous error For more information about this error, try `rustc --explain E0308`.