Proposal: __traits(getComment, symbol)

[FeepingCreature]

I propose a way to get the comment on a symbol at compile time. I 
believe this was already rejected, though I don't know why; I'd 
expect it to be something like "code should not change behavior 
due to a comment." I think that now that we have user-defined 
annotations there is a much lower risk of that.

Why do I want this? Generating special documentation/annotated 
interfaces from D code is a *lot* easier if you can get the 
compiler to do your introspection work for you. I want to 
generate Swagger files documenting our REST services, and I want 
to use D comments to document them. Right now, I will have to do 
a weird hybrid dance where I generate the D type graph on the D 
side with compiletime introspection, output it to a file, 
simultaneously generate the Ddoc JSON file with -D -X to fish out 
the comments, then fuse the two together. There is no need for 
this, but for the absence of __traits(getComment).