error[E0600]: cannot apply unary operator `-` to type `std::string::String`
  --> $DIR/minus-string.rs:13:13
   |
LL | fn main() { -"foo".to_string(); }
   |             ^^^^^^^^^^^^^^^^^^ cannot apply unary operator `-`
   |
   = note: an implementation of `std::ops::Neg` might be missing for `std::string::String`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0600`.