#[macro_export]
macro_rules! ice {
  // If the invocation includes a label...
  ($label:ident => $expr:expr) => {
      // ...define a named function whose definition will never be inlined...
    #[cold]
    #[inline(never)]
    fn $label<T, F: FnOnce() -> T>(f: F) -> T {
        f()
    }
      // ...and then wrap our `expr` in a closure and pass it to the function.
    $label(|| $expr)
  };
    // If no label is specified, just define a closure to do the same thing.
  ($expr:expr) => {
    {
        // Closures that are passed in argument position are allowed to have annotations for
        // obscure historical reasons.
      let closure = core::convert::identity(#[cold] #[inline(never)] || $expr);
      closure()
    }
  };
}