Revert "[Clang][Sema] Always use latest redeclaration of primary template" (#114304)

Clang importer doesn't seem to work well with this change, see
discussion in the original PR.

Reverts llvm/llvm-project#114258

6 files changed, 18 insertions, 72 deletions

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index cd173d1..8691376 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -2708,7 +2708,7 @@ VarDecl *VarDecl::getTemplateInstantiationPattern() const {
     if (isTemplateInstantiation(VDTemplSpec->getTemplateSpecializationKind())) {
       auto From = VDTemplSpec->getInstantiatedFrom();
       if (auto *VTD = From.dyn_cast<VarTemplateDecl *>()) {
-        while (!VTD->isMemberSpecialization()) {
+        while (!VTD->hasMemberSpecialization()) {
           if (auto *NewVTD = VTD->getInstantiatedFromMemberTemplate())
             VTD = NewVTD;
           else
@@ -2718,7 +2718,7 @@ VarDecl *VarDecl::getTemplateInstantiationPattern() const {
       }
       if (auto *VTPSD =
               From.dyn_cast<VarTemplatePartialSpecializationDecl *>()) {
-        while (!VTPSD->isMemberSpecialization()) {
+        while (!VTPSD->hasMemberSpecialization()) {
           if (auto *NewVTPSD = VTPSD->getInstantiatedFromMember())
             VTPSD = NewVTPSD;
           else
@@ -2732,7 +2732,7 @@ VarDecl *VarDecl::getTemplateInstantiationPattern() const {
   // If this is the pattern of a variable template, find where it was
   // instantiated from. FIXME: Is this necessary?
   if (VarTemplateDecl *VTD = VD->getDescribedVarTemplate()) {
-    while (!VTD->isMemberSpecialization()) {
+    while (!VTD->hasMemberSpecialization()) {
       if (auto *NewVTD = VTD->getInstantiatedFromMemberTemplate())
         VTD = NewVTD;
       else
@@ -4153,7 +4153,7 @@ FunctionDecl::getTemplateInstantiationPattern(bool ForDefinition) const {
   if (FunctionTemplateDecl *Primary = getPrimaryTemplate()) {
     // If we hit a point where the user provided a specialization of this
     // template, we're done looking.
-    while (!ForDefinition || !Primary->isMemberSpecialization()) {
+    while (!ForDefinition || !Primary->hasMemberSpecialization()) {
       if (auto *NewPrimary = Primary->getInstantiatedFromMemberTemplate())
         Primary = NewPrimary;
       else
@@ -4170,7 +4170,7 @@ FunctionTemplateDecl *FunctionDecl::getPrimaryTemplate() const {
   if (FunctionTemplateSpecializationInfo *Info
         = TemplateOrSpecialization
             .dyn_cast<FunctionTemplateSpecializationInfo*>()) {
-    return Info->getTemplate()->getMostRecentDecl();
+    return Info->getTemplate();
   }
   return nullptr;
 }
diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index 1c92fd9..db0ea62 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -2030,7 +2030,7 @@ const CXXRecordDecl *CXXRecordDecl::getTemplateInstantiationPattern() const {
   if (auto *TD = dyn_cast<ClassTemplateSpecializationDecl>(this)) {
     auto From = TD->getInstantiatedFrom();
     if (auto *CTD = From.dyn_cast<ClassTemplateDecl *>()) {
-      while (!CTD->isMemberSpecialization()) {
+      while (!CTD->hasMemberSpecialization()) {
         if (auto *NewCTD = CTD->getInstantiatedFromMemberTemplate())
           CTD = NewCTD;
         else
@@ -2040,7 +2040,7 @@ const CXXRecordDecl *CXXRecordDecl::getTemplateInstantiationPattern() const {
     }
     if (auto *CTPSD =
             From.dyn_cast<ClassTemplatePartialSpecializationDecl *>()) {
-      while (!CTPSD->isMemberSpecialization()) {
+      while (!CTPSD->hasMemberSpecialization()) {
         if (auto *NewCTPSD = CTPSD->getInstantiatedFromMemberTemplate())
           CTPSD = NewCTPSD;
         else
diff --git a/clang/lib/AST/DeclTemplate.cpp b/clang/lib/AST/DeclTemplate.cpp
index 1db02d0..755ec72 100644
--- a/clang/lib/AST/DeclTemplate.cpp
+++ b/clang/lib/AST/DeclTemplate.cpp
@@ -993,17 +993,7 @@ ClassTemplateSpecializationDecl::getSpecializedTemplate() const {
   if (const auto *PartialSpec =
           SpecializedTemplate.dyn_cast<SpecializedPartialSpecialization*>())
     return PartialSpec->PartialSpecialization->getSpecializedTemplate();
-  return SpecializedTemplate.get<ClassTemplateDecl *>()->getMostRecentDecl();
-}
-
-llvm::PointerUnion<ClassTemplateDecl *,
-                   ClassTemplatePartialSpecializationDecl *>
-ClassTemplateSpecializationDecl::getSpecializedTemplateOrPartial() const {
-  if (const auto *PartialSpec =
-          SpecializedTemplate.dyn_cast<SpecializedPartialSpecialization *>())
-    return PartialSpec->PartialSpecialization->getMostRecentDecl();
-
-  return SpecializedTemplate.get<ClassTemplateDecl *>()->getMostRecentDecl();
+  return SpecializedTemplate.get<ClassTemplateDecl*>();
 }
 
 SourceRange
@@ -1293,39 +1283,6 @@ VarTemplateDecl::newCommon(ASTContext &C) const {
   return CommonPtr;
 }
 
-void VarTemplateDecl::mergePrevDecl(VarTemplateDecl *Prev) {
-  // If we haven't created a common pointer yet, then it can just be created
-  // with the usual method.
-  if (!getCommonPtrInternal())
-    return;
-
-  Common *ThisCommon = static_cast<Common *>(getCommonPtrInternal());
-  Common *PrevCommon = nullptr;
-  SmallVector<VarTemplateDecl *, 8> PreviousDecls;
-  for (; Prev; Prev = Prev->getPreviousDecl()) {
-    if (CommonBase *C = Prev->getCommonPtrInternal()) {
-      PrevCommon = static_cast<Common *>(C);
-      break;
-    }
-    PreviousDecls.push_back(Prev);
-  }
-
-  // If the previous redecl chain hasn't created a common pointer yet, then just
-  // use this common pointer.
-  if (!PrevCommon) {
-    for (auto *D : PreviousDecls)
-      D->setCommonPtr(ThisCommon);
-    return;
-  }
-
-  // Ensure we don't leak any important state.
-  assert(ThisCommon->Specializations.empty() &&
-         ThisCommon->PartialSpecializations.empty() &&
-         "Can't merge incompatible declarations!");
-
-  setCommonPtr(PrevCommon);
-}
-
 VarTemplateSpecializationDecl *
 VarTemplateDecl::findSpecialization(ArrayRef<TemplateArgument> Args,
                                     void *&InsertPos) {
@@ -1448,16 +1405,7 @@ VarTemplateDecl *VarTemplateSpecializationDecl::getSpecializedTemplate() const {
   if (const auto *PartialSpec =
           SpecializedTemplate.dyn_cast<SpecializedPartialSpecialization *>())
     return PartialSpec->PartialSpecialization->getSpecializedTemplate();
-  return SpecializedTemplate.get<VarTemplateDecl *>()->getMostRecentDecl();
-}
-
-llvm::PointerUnion<VarTemplateDecl *, VarTemplatePartialSpecializationDecl *>
-VarTemplateSpecializationDecl::getSpecializedTemplateOrPartial() const {
-  if (const auto *PartialSpec =
-          SpecializedTemplate.dyn_cast<SpecializedPartialSpecialization *>())
-    return PartialSpec->PartialSpecialization->getMostRecentDecl();
-
-  return SpecializedTemplate.get<VarTemplateDecl *>()->getMostRecentDecl();
+  return SpecializedTemplate.get<VarTemplateDecl *>();
 }
 
 SourceRange VarTemplateSpecializationDecl::getSourceRange() const {
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 3e8b76e..f8e5f3c 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4696,10 +4696,8 @@ void Sema::MergeVarDecl(VarDecl *New, LookupResult &Previous) {
 
   // Keep a chain of previous declarations.
   New->setPreviousDecl(Old);
-  if (NewTemplate) {
-    NewTemplate->mergePrevDecl(OldTemplate);
+  if (NewTemplate)
     NewTemplate->setPreviousDecl(OldTemplate);
-  }
 
   // Inherit access appropriately.
   New->setAccess(Old->getAccess());
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index e2a59f6..573e90a 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -9954,7 +9954,7 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
     auto SynthesizeAggrGuide = [&](InitListExpr *ListInit) {
       auto *Pattern = Template;
       while (Pattern->getInstantiatedFromMemberTemplate()) {
-        if (Pattern->isMemberSpecialization())
+        if (Pattern->hasMemberSpecialization())
           break;
         Pattern = Pattern->getInstantiatedFromMemberTemplate();
       }
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index de0ec01..b630638 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -343,7 +343,7 @@ struct TemplateInstantiationArgumentCollecter
       // If this function was instantiated from a specialized member that is
       // a function template, we're done.
       assert(FD->getPrimaryTemplate() && "No function template?");
-      if (FD->getPrimaryTemplate()->isMemberSpecialization())
+      if (FD->getPrimaryTemplate()->hasMemberSpecialization())
         return Done();
 
       // If this function is a generic lambda specialization, we are done.
@@ -442,11 +442,11 @@ struct TemplateInstantiationArgumentCollecter
         Specialized = CTSD->getSpecializedTemplateOrPartial();
     if (auto *CTPSD =
             Specialized.dyn_cast<ClassTemplatePartialSpecializationDecl *>()) {
-      if (CTPSD->isMemberSpecialization())
+      if (CTPSD->hasMemberSpecialization())
         return Done();
     } else {
       auto *CTD = Specialized.get<ClassTemplateDecl *>();
-      if (CTD->isMemberSpecialization())
+      if (CTD->hasMemberSpecialization())
         return Done();
     }
     return UseNextDecl(CTSD);
@@ -478,11 +478,11 @@ struct TemplateInstantiationArgumentCollecter
         Specialized = VTSD->getSpecializedTemplateOrPartial();
     if (auto *VTPSD =
             Specialized.dyn_cast<VarTemplatePartialSpecializationDecl *>()) {
-      if (VTPSD->isMemberSpecialization())
+      if (VTPSD->hasMemberSpecialization())
         return Done();
     } else {
       auto *VTD = Specialized.get<VarTemplateDecl *>();
-      if (VTD->isMemberSpecialization())
+      if (VTD->hasMemberSpecialization())
         return Done();
     }
     return UseNextDecl(VTSD);
@@ -4141,7 +4141,7 @@ getPatternForClassTemplateSpecialization(
   CXXRecordDecl *Pattern = nullptr;
   Specialized = ClassTemplateSpec->getSpecializedTemplateOrPartial();
   if (auto *CTD = Specialized.dyn_cast<ClassTemplateDecl *>()) {
-    while (!CTD->isMemberSpecialization()) {
+    while (!CTD->hasMemberSpecialization()) {
       if (auto *NewCTD = CTD->getInstantiatedFromMemberTemplate())
         CTD = NewCTD;
       else
@@ -4151,7 +4151,7 @@ getPatternForClassTemplateSpecialization(
   } else if (auto *CTPSD =
                  Specialized
                      .dyn_cast<ClassTemplatePartialSpecializationDecl *>()) {
-    while (!CTPSD->isMemberSpecialization()) {
+    while (!CTPSD->hasMemberSpecialization()) {
       if (auto *NewCTPSD = CTPSD->getInstantiatedFromMemberTemplate())
         CTPSD = NewCTPSD;
       else