[Clang] fixed clang frontend crash with friend class declaration and overload == (#133878)

Author: Ankur-0429

clang/docs/ReleaseNotes.rst

@@ -365,6 +365,7 @@ Bug Fixes to Attribute Support
 Bug Fixes to C++ Support
 ^^^^^^^^^^^^^^^^^^^^^^^^
 
+- Clang now supports implicitly defined comparison operators for friend declarations. (#GH132249)
 - Clang now diagnoses copy constructors taking the class by value in template instantiations. (#GH130866)
 - Clang is now better at keeping track of friend function template instance contexts. (#GH55509)
 - Clang now prints the correct instantiation context for diagnostics suppressed

clang/lib/Sema/SemaDeclCXX.cpp

@@ -9006,8 +9006,7 @@ bool Sema::CheckExplicitlyDefaultedComparison(Scope *S, FunctionDecl *FD,
       return true;
 
     if (llvm::none_of(RD->friends(), [&](const FriendDecl *F) {
-          return FD->getCanonicalDecl() ==
-                 F->getFriendDecl()->getCanonicalDecl();
+          return declaresSameEntity(F->getFriendDecl(), FD);
         })) {
       Diag(FD->getLocation(), diag::err_defaulted_comparison_not_friend)
           << int(DCK) << int(0) << RD;

clang/test/CXX/class/class.compare/class.compare.default/p1.cpp

@@ -285,3 +285,15 @@ struct j {
 };
 bool j::operator==(const j &) const = default;
 }
+
+namespace evil2 {
+  struct k {
+  };
+  
+  struct l {
+      friend bool operator==(const l& a, const l& b);
+      friend class k;
+  };
+  
+  bool operator==(const l& a, const l& b) = default;
+}