[clang] Sema: filter out invalid base-specifiers before attaching (PR #147213)

[Corentin Jabot via cfe-commits]

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@@ -923,6 +923,7 @@ Bug Fixes to C++ Support
 - Improved handling of variables with ``consteval`` constructors, to
   consistently treat the initializer as manifestly constant-evaluated.
   (#GH135281)
+- Switch `ParseBaseClause` to use `BaseResult::isUsable()` instead of `isInvalid()`, fixing dropped or mis-parsed base specifiers in C++ classes. (#GH147186)
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cor3ntin wrote:

```suggestion
- Fix a crash in the presence of invalid base classes. (#GH147186)
```

Release notes are meant to be user-facing

https://github.com/llvm/llvm-project/pull/147213