error[E0046]: not all trait items implemented, missing: `foo` --> $DIR/dont-project-to-rpitit-with-no-value.rs:11:1 | LL | fn foo(&self) -> impl Sized; | ---------------------------- `foo` from trait ... LL | impl MyTrait for i32 { | ^^^^^^^^^^^^^^^^^^^^ missing `foo` in implementation error: aborting due to previous error For more information about this error, try `rustc --explain E0046`.