Following code should work as expected.

void main()
{
    // lambda has a qualified parameter that needs type inference
    void foo1(void delegate(ref int ) dg){ int x=10; dg(x); }
    foo1((ref x){ assert(x == 10); });
    // test.d(4): Error: undefined identifier x
    // Assertion failure: 'typen->deco' on line 1690 in file 'cast.c'
    
    // lambda has C style variadic
    void foo2(void delegate(int, ...) dg){ dg(20, 3.14); }
    foo2((x,...){ assert(x == 20); });
    // OK

    // lambda has D style type safe variadic
    void foo3(void delegate(int[]...) dg){ dg(1, 2, 3); }
    foo3((x ...){ assert(x == [1,2,3]); });
    // test.d(16): Error: undefined identifier x
    // Assertion failure: 'typen->deco' on line 1690 in file 'cast.c'
}