tests.d

template Tuple(T...) { alias T Tuple; }
template Select(bool b, T, U) { static if (b) alias T Select; else alias U Select; }

void main()
{
    static bool isEq (T1, T2)(T1 s1, T2 s2) { return s1 == s2; }
    static bool isNeq(T1, T2)(T1 s1, T2 s2) { return s1 != s2; }

    foreach (b1; Tuple!(false, true))
        foreach (b2; Tuple!(false, true))
        {
            assert( isEq (cast(Select!(b1, string, char[1]))"a", cast(Select!(b2, string, char[1]))"a" ));
            assert(!isNeq(cast(Select!(b1, string, char[1]))"a", cast(Select!(b2, string, char[1]))"a" ));
            assert(!isEq (cast(Select!(b1, string, char[1]))"a", cast(Select!(b2, string, char[1]))"b" ));
            assert( isNeq(cast(Select!(b1, string, char[1]))"a", cast(Select!(b2, string, char[1]))"b" ));
            assert(!isEq (cast(Select!(b1, string, char[1]))"a", cast(Select!(b2, string, char[2]))"aa"));
            assert( isNeq(cast(Select!(b1, string, char[1]))"a", cast(Select!(b2, string, char[2]))"aa"));

            // Note: order of evaluation was not followed before this patch
            // (thus, the test below will fail without the patch).
            // Although the specification mentions that as implementation-defined behavior,
            // I understand that this isn't by design, but rather an inconvenient aspect of DMD
            // that has been moved to the specification.
            int order = 0;
            auto getS1()() { assert(order==0); order++; return cast(Select!(b1, string, char[1]))"a"; }
            auto getS2()() { assert(order==1); order++; return cast(Select!(b2, string, char[1]))"a"; }
            bool result = getS1() == getS2();
            assert(result);
            assert(order == 2);
        }
}