error: Undefined Behavior: constructing invalid value: encountered $HEX, but expected a valid unicode scalar value (in `0..=$HEX` but not in `$HEX..=$HEX`)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered $HEX, but expected a valid unicode scalar value (in `0..=$HEX` but not in `$HEX..=$HEX`)