error[E0178]: expected a path on the left-hand side of `+`, not `&'a Foo` --> $DIR/E0178.rs:6:8 | LL | w: &'a Foo + Copy, | ^^^^^^^^^^^^^^ help: try adding parentheses: `&'a (Foo + Copy)` error[E0178]: expected a path on the left-hand side of `+`, not `&'a Foo` --> $DIR/E0178.rs:7:8 | LL | x: &'a Foo + 'a, | ^^^^^^^^^^^^ help: try adding parentheses: `&'a (Foo + 'a)` error[E0178]: expected a path on the left-hand side of `+`, not `&'a mut Foo` --> $DIR/E0178.rs:8:8 | LL | y: &'a mut Foo + 'a, | ^^^^^^^^^^^^^^^^ help: try adding parentheses: `&'a mut (Foo + 'a)` error[E0178]: expected a path on the left-hand side of `+`, not `fn() -> Foo` --> $DIR/E0178.rs:9:8 | LL | z: fn() -> Foo + 'a, | ^^^^^^^^^^^^^^^^ perhaps you forgot parentheses? error: aborting due to 4 previous errors For more information about this error, try `rustc --explain E0178`.