[clang-tools-extra] [clang-doc] add a JSON generator (PR #142483)

[Paul Kirth via cfe-commits]

ilovepi wrote:

> If we're open to adding a flag in the base `Info` like `IsClassSpecialization`, then we can probably easily deal with these by trying to reconstruct the specialization's arguments (will be something like "Foo<T, int>.json"). Functions don't produce their own files so function specializations wont be a problem. Then we can keep this layout. @ilovepi
> 
> That or we manually change the name when serializing during mapping. I'm not so sure how well merging the infos would be ergonomically. Specializations can have all of their own unique members and methods which need documentation.
> 

This sounds promising. I'm fine w/ adding a field to track this. BTW, what does clang do? I'm wondering if we should track more than 1-bit of info here. 

> I also found a way to get a nice ugly mangled name :)

Nice! IIRC that's what I've seen a lot of document generators use. If its unique enough for ODR, is probably good enough for docs ... right?

https://github.com/llvm/llvm-project/pull/142483