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 a bound introduced by this call | = help: the following other types implement trait `UpperHex`: &T &mut T NonZeroI128 NonZeroI16 NonZeroI32 NonZeroI64 NonZeroI8 NonZeroIsize and 21 others = note: required for `&str` to implement `UpperHex` note: required by a bound in `core::fmt::ArgumentV1::<'a>::new_upper_hex` --> $SRC_DIR/core/src/fmt/mod.rs:LL:COL = note: this error originates in the macro `$crate::__export::format_args` which comes from the expansion of the macro `arg_new` (in Nightly builds, run with -Z macro-backtrace for more info) error: aborting due to previous error For more information about this error, try `rustc --explain E0277`.