def match_set(self, tokens, item):
        """Matches a set."""
        match, = tokens
        self.add_check("_coconut.isinstance(" + item + ", _coconut.abc.Set)")
        self.add_check("_coconut.len(" + item + ") == " + str(len(match)))
        for const in match:
            self.add_check(const + " in " + item)