[Clang] prevent errors for deduction guides using deduced type aliases (#117450)

Fixes #54909

--- 

Clang incorrectly produces diagnostics for alias templates in deduction
guides, treating them as separate from their underlying types. This
issue arises because Clang doesn't properly handle
`TypeAliasTemplateDecl` when comparing template names for equality in
the context of deduction guides, resulting in diagnostics that don't
align with the C++ standard. As the C++ standard specifies - _an alias
template is considered a synonym for its underlying type_

With this change, Clang now correctly resolves alias templates to their
underlying types in deduction guides, ensuring compliance with the C++
standard.
3 files changed
tree: f4bcf0c503968fc6413ee1b5553b8f8a471d5603
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. libc/
  11. libclc/
  12. libcxx/
  13. libcxxabi/
  14. libunwind/
  15. lld/
  16. lldb/
  17. llvm/
  18. llvm-libgcc/
  19. mlir/
  20. offload/
  21. openmp/
  22. polly/
  23. pstl/
  24. runtimes/
  25. third-party/
  26. utils/
  27. .clang-format
  28. .clang-tidy
  29. .git-blame-ignore-revs
  30. .gitattributes
  31. .gitignore
  32. .mailmap
  33. CODE_OF_CONDUCT.md
  34. CONTRIBUTING.md
  35. LICENSE.TXT
  36. pyproject.toml
  37. README.md
  38. SECURITY.md
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