How to make a struct containing an associative array to deeply copy (for repeated usage in foreach) ?

[rkompass]

@bachmeier
> You're not the first one. There's no technical reason for the 
> restriction. It's simply a matter of being opposed by those who 
> make these decisions on the basis that it's the wrong way to 
> program or something like that. Here is a recent thread: 
> https://forum.dlang.org/post/ikwphfwevgnsxmdfqqkl@forum.dlang.org

Thank you for this. Very interesting discussion. And apparently a 
deliberate restriction of flexibility in type conversion.

I will first try to understand better how templates work under 
the hood before joining this discussion.

Given the types S and T in say `templfunc(S, T)(S arg1, T arg2) 
{}`
represent 2 different actual types in the program, does that mean 
that there are 4 versions of the `templfunc` function compiled 
in? (This was the C++ way iirc).
Or are the types T and S are put on the stack like ordinary 
arguments and the usage of arg1 and arg2 within the function is 
enveloped in switches that query these Types?