how can i mixin a function as struct or class member function

[mycybyby via Digitalmars-d-learn]

for example:

    function void a(int i) {
        writeln(i);
    }

    auto JSFunction(alias F)() if(isSomeFunction!F) {
        class S {
        public ReturnType!F dg(ParameterTypeTuple!F) {
                mixin(F.body) // what should i do ???
            }
        }
    }

thank you