error[E0277]: the trait bound `str: std::fmt::UpperHex` is not satisfied
  --> $DIR/ifmt-unimpl.rs:12:21
   |
LL |     format!("{:X}", "3");
   |                     ^^^ the trait `std::fmt::UpperHex` is not implemented for `str`
   |
   = note: required because of the requirements on the impl of `std::fmt::UpperHex` for `&str`
   = note: required by `std::fmt::UpperHex::fmt`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.