fn montgomery_to_edwards_rejects_twist()

in src/montgomery.rs [365:379]

• 10 lines of code
• 2 McCabe index (conditional complexity)

    fn montgomery_to_edwards_rejects_twist() {
        let one = FieldElement::one();

        // u = 2 corresponds to a point on the twist.
        let two = MontgomeryPoint((&one+&one).to_bytes());

        assert!(two.to_edwards(0).is_none());

        // u = -1 corresponds to a point on the twist, but should be
        // checked explicitly because it's an exceptional point for the
        // birational map.  For instance, libsignal will accept it.
        let minus_one = MontgomeryPoint((-&one).to_bytes());

        assert!(minus_one.to_edwards(0).is_none());
    }