import std.traits;

​

void something(T, string property)() {

​

  // in THIS context is T a class

  // property = "data"

​

  alias S = __traits(getMember, T, property);

​

  // typeof(S) = foo!bar

​

  static if (isCallable!S) {

      // some other magic

  }

​

  // ...

​

}

​

​

// We need "a class" with a member named "data"

class C

{

    // This is going to be `alias S`, so its type must be foo!bar

    foo!bar data;

}

​

// Now we need a type named "bar"

// We know it's going to be used as an argument to `foo`, so let's look there for clues

​

struct foo(T) {

  T get() {

        static if (is(T : bar)) {

            // `bar` can be compared to null, so it must be a reference type

            // That means it's probably a class

            if (value is null) {

                value = fun!T("id", 123);

            }

        }

        return value;

    }

    T value;

    alias get this;

}

​

// We don't know anything else about `bar`, so leave it empty for now

class bar { }

​

// Now let's try instantiating `something`

alias test = something!(C, "data");

​

TDobj fun(TDobj, T)(string propertyName, T needle) if (is(TDobj : bar)) {

   TDobj[] list = loadAllMatched!TDobj(propertyName, needle, 1);

   return list.length > 0 ? list[0] : null;

}

​

// No idea what this is suppose to do, but we can match the signature

TDobj[] loadAllMatched(TDobj, T)(string propertyName, T needle, int i) {

    return TDobj[].init;

}