[Clang] Don't form a type constraint if the concept is invalid (#122065)

After 0dedd6fe1 and 03229e7c0, invalid concept declarations might lack
expressions for evaluation and normalization. This could make it crash
in certain scenarios, apart from the one of evaluation concepts showed
in 03229e7c0, there's also an issue when checking specializations where
the normalization also relies on a non-null expression.

This patch prevents that by avoiding building up a type constraint in
such situations, thereafter the template parameter wouldn't have a
concept specialization of a null expression.

With this patch, the assumption in ASTWriterDecl is no longer valid.
Namely, HasConstraint and TypeConstraintInitialized must now represent
different meanings for both source fidelity and semantic requirements.

Fixes https://github.com/llvm/llvm-project/issues/115004
Fixes https://github.com/llvm/llvm-project/issues/121980
4 files changed
tree: faf4c92ac2ce90f93eb12f7d1dbb6c3dcd342935
  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
README.md

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