How do you debug @safe @nogc code? Can't figure out how to print.

[aliak]

Hi, I previously had trouble trying to get print statements 
working while debugging in nogc. And that was hackishly solved 
[0], but I can't figure out how to do the same if I have @safe 
involved. Here's a cut down sample:

// This is the function from the thread referenced
auto assumeNoGC(T)(T t) {
     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) {
             import std.stdio;
             // Print args here for debugging purposes
             assumeNoGC({ writeln(args); })();
             return 3;
         }
     }
}

@safe @nogc void main() {
     auto i = Dispatcher().getI(3);
}

So, basically with the above, using:
     debug writeln(args);
Causes "Error: @nogc function D main cannot call non- at nogc 
function"

Using:
     debug assumeNoGC({ writeln(args); })();
Causes:
     Error: @safe function D main cannot call @system function
     Error: @nogc function D main cannot call non- at nogc function

Changing attrs in assumeNoGC
     enum attrs = functionAttributes!T | FunctionAttribute.nogc | 
FunctionAttribute.safe
Causes same as previous errors

Adding @trusted to declaration of opDispatch gets rid of @safe 
error but I still get "Error: @nogc function D main cannot call 
non- at nogc function". And going through the codebase and figuring 
out where to add @trusted is *very* cumbersome.

I can't figure out how to make this work. The ideal way would be 
just a debug_print() function that works in nogc and safe code. 
I.e. does not affect the attribute inference of templates.

Cheers,
- Ali

[0] https://forum.dlang.org/post/pmf4dm$jmo$1@digitalmars.com