Function extern_spec_i128_checked_sub 

pub fn extern_spec_i128_checked_sub(self_: i128, rhs: i128) -> Option<i128>

extern spec for i128::checked_sub

This is not a real function: its only use is for documentation.

terminates

ghost

ensures

(result == None)
                    == ((self@ $op rhs@) < $type::MIN@ || (self@ $op rhs@) > $type::MAX@)

ensures

forall<r: $type> result == Some(r) ==> r@ == (self@ $op rhs@)