error: Undefined Behavior: writing to ALLOC which is read-only
  --> $DIR/modifying_constants.rs:LL:CC
   |
LL |     *y = 42;
   |     ^^^^^^^ writing to ALLOC which is read-only
   |
   = 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/modifying_constants.rs:LL:CC

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

error: aborting due to previous error