[Clang] use parent declaration context to avoid asserting cast failure in defaulted comparison method

Author: a-tarasyuk

clang/docs/ReleaseNotes.rst

@@ -889,7 +889,7 @@ Bug Fixes to C++ Support
   between the addresses of two labels (a GNU extension) to a pointer within a constant expression. (#GH95366).
 - Fix immediate escalation bugs in the presence of dependent call arguments. (#GH94935)
 - Clang now diagnoses explicit specializations with storage class specifiers in all contexts.
-
+- Fixed failed assertion when resolving context of defaulted comparison method outside of struct. (#GH96043).
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/Sema/SemaDeclCXX.cpp

@@ -9192,7 +9192,7 @@ ComputeDefaultedComparisonExceptionSpec(Sema &S, SourceLocation Loc,
     EnterExpressionEvaluationContext Context(
         S, Sema::ExpressionEvaluationContext::Unevaluated);
 
-    CXXRecordDecl *RD = cast<CXXRecordDecl>(FD->getLexicalParent());
+    CXXRecordDecl *RD = cast<CXXRecordDecl>(FD->getDeclContext());
     SourceLocation BodyLoc =
         FD->getEndLoc().isValid() ? FD->getEndLoc() : FD->getLocation();
     StmtResult Body =

clang/test/SemaCXX/defaulted-comparison-struct.cpp

@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+template <typename> class a {};
+template <typename b> b c(a<b>);
+template <typename d> class e {
+public:
+  typedef a<d *> f;
+  f begin();
+};
+template <typename d, typename g> constexpr bool operator==(d h, g i) {
+  return *c(h.begin()) == *c(i.begin());
+}
+struct j {
+  e<j> bar;
+  bool operator==(const j &) const;
+};
+bool j::operator==(const j &) const = default;