import std.stdio;

import std.traits;

​

auto assumeNoGC(T)(return scope T t) @trusted {

    import std.traits;

    enum attrs = functionAttributes!T | FunctionAttribute.nogc;

    return cast(SetFunctionAttributes!(T, functionLinkage!T, attrs)) t;

}

​

private struct Dispatcher {

    public template opDispatch(string name){

        auto ref opDispatch(Args...)(auto ref Args args) {

            //assumeNoGC({ writefln("%d", 42); })(); // This works now

            debug {

                writefln("%d", 42);

            }

            return 3;

        }

    }

}

​

@safe @nogc void main() {

    auto i = Dispatcher().getI(3);

}