Address http://bugs.llvm.org/pr30994 so that a non-friend can properly replace a friend, and a visible friend can properly replace an invisible friend but not vice verse, and definitions are not replaced. This fixes the two FIXME in SemaTemplate/friend-template.cpp.

The code implements Richard Smith suggestion in comment 3 of the PR.

reviewer: Vassil Vassilev

Differential Revision: https://reviews.llvm.org/D31540

llvm-svn: 300443

2 files changed, 19 insertions, 0 deletions

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 2b22e5bb50a..6a288cdb21f 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -1536,6 +1536,10 @@ bool NamedDecl::declarationReplaces(NamedDecl *OldD, bool IsKnownNewer) const {
   if (isa<ObjCMethodDecl>(this))
     return false;
 
+  if (getFriendObjectKind() > OldD->getFriendObjectKind() &&
+      !isThisDeclarationADefinition())
+    return false;
+
   // For parameters, pick the newer one. This is either an error or (in
   // Objective-C) permitted as an extension.
   if (isa<ParmVarDecl>(this))
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index cda70c5edcd..ae7444579b0 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -861,6 +861,21 @@ const FunctionType *Decl::getFunctionType(bool BlocksToo) const {
   return Ty->getAs<FunctionType>();
 }
 
+bool Decl::isThisDeclarationADefinition() const {
+  if (auto *TD = dyn_cast<TagDecl>(this))
+    return TD->isThisDeclarationADefinition();
+  if (auto *FD = dyn_cast<FunctionDecl>(this))
+    return FD->isThisDeclarationADefinition();
+  if (auto *VD = dyn_cast<VarDecl>(this))
+    return VD->isThisDeclarationADefinition();
+  if (auto *CTD = dyn_cast<ClassTemplateDecl>(this))
+    return CTD->isThisDeclarationADefinition();
+  if (auto *FTD = dyn_cast<FunctionTemplateDecl>(this))
+    return FTD->isThisDeclarationADefinition();
+  if (auto *VTD = dyn_cast<VarTemplateDecl>(this))
+    return VTD->isThisDeclarationADefinition();
+  return false;
+}
 
 /// Starting at a given context (a Decl or DeclContext), look for a
 /// code context that is not a closure (a lambda, block, etc.).