error: Undefined Behavior: constructing invalid value: encountered $HEX, but expected a valid unicode scalar value (in `0..=$HEX` but not in `$HEX..=$HEX`)
  --> $DIR/invalid_char.rs:LL:CC
   |
LL |     let _val = match unsafe { std::mem::transmute::<i32, char>(-1) } {
   |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered $HEX, but expected a valid unicode scalar value (in `0..=$HEX` but not in `$HEX..=$HEX`)
   |
   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
   = note: BACKTRACE:
   = note: inside `main` at $DIR/invalid_char.rs:LL:CC

note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

error: aborting due to previous error