message: some error classes should be impossible
diff: @@ -217,6 +217,8 @@ pub fn eval_main<'tcx>(tcx: TyCtxt<'tcx>, main_id: DefId, config: MiriConfig) ->
  }
  err_unsup!(NoMirFor(..)) =>
  format!("{}. Did you set `MIRI_SYSROOT` to a Miri-enabled sysroot? You can prepare one with `cargo miri setup`.", e),
  + InterpError::Panic(_) | InterpError::InvalidProgram(_) =>
  + bug!("This error should be impossible in Miri: {}", e),
  _ => e.to_string()
  };
  e.print_backtrace();
  