|  | error[E0277]: the trait bound `str: UpperHex` is not satisfied | 
|  | --> $DIR/ifmt-unimpl.rs:2:21 | 
|  | | | 
|  | LL |     format!("{:X}", "3"); | 
|  | |              ----   ^^^ the trait `UpperHex` is not implemented for `str` | 
|  | |              | | 
|  | |              required by this formatting parameter | 
|  | | | 
|  | = help: the following other types implement trait `UpperHex`: | 
|  | &T | 
|  | &mut T | 
|  | NonZero<T> | 
|  | Saturating<T> | 
|  | Wrapping<T> | 
|  | i128 | 
|  | i16 | 
|  | i32 | 
|  | and 9 others | 
|  | = note: required for `&str` to implement `UpperHex` | 
|  | = note: this error originates in the macro `$crate::__export::format_args` which comes from the expansion of the macro `format` (in Nightly builds, run with -Z macro-backtrace for more info) | 
|  |  | 
|  | error: aborting due to 1 previous error | 
|  |  | 
|  | For more information about this error, try `rustc --explain E0277`. |