error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types --> $DIR/suggest-return-future.rs:7:13 | LL | fn foo() -> _ { | ^ | | | not allowed in type signatures | help: replace with an appropriate return type: `impl Future` error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types --> $DIR/suggest-return-future.rs:15:13 | LL | fn bar() -> _ { | ^ | | | not allowed in type signatures | help: replace with an appropriate return type: `impl Future` error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0121`.