[clang] [clang-tools-extra] [clang] Implement CWG2398 provisional TTP matching to class templates (PR #92855)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

> Heads up: this commit has triggered some weird errors for a compile, but only when clang header modules are enabled. 
> That seems to _probably_ indicate a bug in this commit (presumably related to AST serialization or deserialization?), but I don't have a test-case, and, that's harder to get for issues that only arise with modules enabled...

Thanks for the heads-up, James.

Indeed, and it's not only modules, our tooling for reducing test cases is getting less and less effective.

https://github.com/llvm/llvm-project/pull/92855