error[E0369]: cannot add `&str` to `&str` --> $DIR/issue-47377.rs:4:14 | LL | let _a = b + ", World!"; | - ^ ---------- &str | | | | | `+` cannot be used to concatenate two `&str` strings | &str | = note: string concatenation requires an owned `String` on the left help: create an owned `String` from a string reference | LL | let _a = b.to_owned() + ", World!"; | +++++++++++ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0369`.