pub type ForRefMut<T: ?Sized> = ForLt<fn(for<'_>) -> &mut T>;
ForRefMut<T> is a macro-free alias for ForLt!(<'any> = &'any mut T).
ForRefMut<T>
ForLt!(<'any> = &'any mut T)
pub struct ForRefMut<T: ?Sized>(/* private fields */);