typedef A1 = (int x, int y);
typedef A2 = (int x, int y);

() test() {
    var A1 a1;
    var A2 a2;
    var (int x, int y) b;
    var (int x, int y, bool z) c;
    var (int, int) d;
    var (int, bool) e;
    var (int p, int q) f;
    var (int p, short q) g;
    
    /* ERRORS: types referenced by name are different => error */
    a1 = a2;
    a2 = a1;
    
    /* ERRORS: different lengths of structs */
    b = c;
    c = b;
    d = c;
    c = d;
    
    /* ERRORS: different types */
    d = e;
    e = d;
    
    /* ERRORS: different member names */
    f = b;
    b = f;
    
    // member types that are subtypes
    // (member types must be equal)
    f = g;  // ERROR
}