debug mixins

[Stefan Koch via Digitalmars-d-learn]

On Wednesday, 15 March 2017 at 03:43:20 UTC, Inquie wrote:
> So, is it possible to debug string mixins?
>
> I ran visual D and tried to step in to a function that was 
> generated by a mixin and it brought an open file dialog box 
> asking me to load the source code where the function was 
> located... of course, it wasn't located anywhere except in the 
> mixin string.
>
>
> This leads to the idea, why can't the compiler simply output 
> the mixin string to a file then the debugger can load that 
> source file?
>
> One of the most frustrating things about D is not having the 
> ability to debug it's powerful meta programming in any 
> reasonable way. (bad enough having to resort to using 
> pragma(msg))
>
> But we can't even debug the results of those meta programming 
> in the case of string mixins because there is no way to step in 
> to them... It seems all the machinery is there, but just a few 
> extra steps are needed.

In dmd ~master. there is an undocumented switch called -vcg-ast.
It will produce a file with everything expanded.
(Only if the code compiles with no errors).
It produces a cg-file which may or may not contain a valid source 
representation of the actual code compiled.