To clarify: When you say “in tree”, you mean development and experimentation will happen on the version of Clang-Tidy at https://github.com/llvm/llvm-project?
This is our plan. We have up until this point done our experimentation in a non-public codebase, but we think we’ve answered enough questions that now is a good point to start upstreaming what we have, continue developing in upstream Clang-Tidy, and get feedback from the community. Also, we already have partners who are interested in evaluating the checks but would need them to be in upstream Clang-Tidy to do so.
Our plan is to clearly identify the two proposed Clang-Tidy checks as experimental in the documentation. We will caution users that we expect to make breaking changes to syntax and semantics and that they should therefore use the checks only for testing and experimentation but not for production use. We will work with our early adopters to help them across breaking changes while the Clang-Tidy check is still experimental. Once we consider the design to be sufficiently stabilized, we will remove this experimental qualification from the checks.
We think this approach makes sense because it allows us to get feedback on the design and implementation incrementally (the feedback on this RFC already shows the value of this), rather than in one “big bang”, as would be the case if we did the development out of tree.