error[E0369]: binary operation `+` cannot be applied to type `&str`
  --> $DIR/issue-39018.rs:12:13
   |
LL |     let x = "Hello " + "World!";
   |             ^^^^^^^^^^^^^^^^^^^ `+` can't be used to concatenate two `&str` strings
help: `to_owned()` can be used to create an owned `String` from a string reference. String concatenation appends the string on the right to the string on the left and may require reallocation. This requires ownership of the string on the left
   |
LL |     let x = "Hello ".to_owned() + "World!";
   |             ^^^^^^^^^^^^^^^^^^^

error[E0369]: binary operation `+` cannot be applied to type `World`
  --> $DIR/issue-39018.rs:18:13
   |
LL |     let y = World::Hello + World::Goodbye;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: an implementation of `std::ops::Add` might be missing for `World`

error[E0369]: binary operation `+` cannot be applied to type `&str`
  --> $DIR/issue-39018.rs:21:13
   |
LL |     let x = "Hello " + "World!".to_owned();
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `+` can't be used to concatenate a `&str` with a `String`
help: `to_owned()` can be used to create an owned `String` from a string reference. String concatenation appends the string on the right to the string on the left and may require reallocation. This requires ownership of the string on the left
   |
LL |     let x = "Hello ".to_owned() + &"World!".to_owned();
   |             ^^^^^^^^^^^^^^^^^^^   ^^^^^^^^^^^^^^^^^^^^

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0369`.