[clang] [clang][Sema] Improve error recovery for id-expressions referencing invalid decls (PR #81662)

[Nathan Ridge via cfe-commits]

HighCommander4 wrote:

> Changing to Draft status as CI is showing some test failures that I will need to investigate:
> 
> ```
> Failed Tests (4):
>   Clang :: OpenMP/nvptx_unsupported_type_messages.cpp
>   Clang :: SemaCXX/constant-expression-cxx11.cpp
>   Clang :: SemaCXX/cxx2b-consteval-if.cpp
>   Clang :: SemaCXX/deduced-return-type-cxx14.cpp
> ```

The failures are related to new diagnostics that are issued as a side effect of running additional checks in BuildDeclarationNameExpr().

Accepting these additional diagnostics would regress some previous changes such as https://github.com/llvm/llvm-project/commit/1cf4541c4f3ae2f6eaadb6d7972cf8cc71118965 and https://reviews.llvm.org/D95928. I think I'll need to find a way to avoid them instead.

https://github.com/llvm/llvm-project/pull/81662