import std.stdio;

​

struct MyType(T) {

    static if (is (T == float)) {

        alias ResultType = double;

​

    } else static if (is (T == double)) {

        alias ResultType = real;

​

    } else {

        alias ResultType = void;

        static assert(false, T.stringof ~ " is not supported");

    }

​

    ResultType doWork() {

        writefln("The return type for %s is %s.",

                 T.stringof, ResultType.stringof);

        ResultType result;

        // ...

        return result;

    }

}

​

void main() {

    auto f = MyType!float();

    f.doWork();

​

    auto d = MyType!double();

    d.doWork();

    auto g = MyType!string();

    g.doWork();

}