80cf576f59
Fix a error suggestion for E0121 when using placeholder _ as return types on function signature. Recommit after refactoring based on comment: https://github.com/rust-lang/rust/pull/126017#issuecomment-2189149361 But when changing return type's lifetime to `ReError` will affect the subsequent borrow check process and cause test11 in typeck_type_placeholder_item.rs to lost E0515 message. ```rust fn test11(x: &usize) -> &_ { //~^ ERROR the placeholder `_` is not allowed within types on item signatures for return types &x //~ ERROR cannot return reference to function parameter(this E0515 msg will disappear) } ``` fixes #125488 r? ``@pnkfelix``