Diagnostic for undocumented public declarations

[xwu (Xiaodi Wu)]

Whatever part of the project that @owenv refers to in the post below seems to have all of the prerequisite knowledge; shouldn't any missing docs or issues be diagnosed as part of that?

The state of Swift documentation

I'm not really convinced we need to coordinate with the closed source docs to make progress in this area. Most of what's been described should be possible using swift symbolgraph-extract, which is available in toolchains from 5.3 onwards and seems designed for this use case. Its output includes doc comments, type relationships, and guidance on how to format headings/subheadings/etc. of documentation pages without needing to make many individual SourceKit requests. For example, this command can …