[modules] When instantiating a class member, don't expect to find the previous

declaration in the instantiation if the previous declaration came from another
definition of the class template that got merged into the pattern definition.

llvm-svn: 219552

1 files changed, 33 insertions, 12 deletions

diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index dce8ca4c8a9..a07f7765fcb 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -261,6 +261,24 @@ void Sema::InstantiateAttrs(const MultiLevelTemplateArgumentList &TemplateArgs,
   }
 }
 
+/// Get the previous declaration of a declaration for the purposes of template
+/// instantiation. If this finds a previous declaration, then the previous
+/// declaration of the instantiation of D should be an instantiation of the
+/// result of this function.
+template<typename DeclT>
+static DeclT *getPreviousDeclForInstantiation(DeclT *D) {
+  DeclT *Result = D->getPreviousDecl();
+
+  // If the declaration is within a class, and the previous declaration was
+  // merged from a different definition of that class, then we don't have a
+  // previous declaration for the purpose of template instantiation.
+  if (Result && isa<CXXRecordDecl>(D->getDeclContext()) &&
+      D->getLexicalDeclContext() != Result->getLexicalDeclContext())
+    return nullptr;
+
+  return Result;
+}
+
 Decl *
 TemplateDeclInstantiator::VisitTranslationUnitDecl(TranslationUnitDecl *D) {
   llvm_unreachable("Translation units cannot be instantiated");
@@ -347,7 +365,7 @@ Decl *TemplateDeclInstantiator::InstantiateTypedefNameDecl(TypedefNameDecl *D,
     }
   }
 
-  if (TypedefNameDecl *Prev = D->getPreviousDecl()) {
+  if (TypedefNameDecl *Prev = getPreviousDeclForInstantiation(D)) {
     NamedDecl *InstPrev = SemaRef.FindInstantiatedDecl(D->getLocation(), Prev,
                                                        TemplateArgs);
     if (!InstPrev)
@@ -370,13 +388,15 @@ Decl *TemplateDeclInstantiator::InstantiateTypedefNameDecl(TypedefNameDecl *D,
 
 Decl *TemplateDeclInstantiator::VisitTypedefDecl(TypedefDecl *D) {
   Decl *Typedef = InstantiateTypedefNameDecl(D, /*IsTypeAlias=*/false);
-  Owner->addDecl(Typedef);
+  if (Typedef)
+    Owner->addDecl(Typedef);
   return Typedef;
 }
 
 Decl *TemplateDeclInstantiator::VisitTypeAliasDecl(TypeAliasDecl *D) {
   Decl *Typedef = InstantiateTypedefNameDecl(D, /*IsTypeAlias=*/true);
-  Owner->addDecl(Typedef);
+  if (Typedef)
+    Owner->addDecl(Typedef);
   return Typedef;
 }
 
@@ -394,7 +414,7 @@ TemplateDeclInstantiator::VisitTypeAliasTemplateDecl(TypeAliasTemplateDecl *D) {
   TypeAliasDecl *Pattern = D->getTemplatedDecl();
 
   TypeAliasTemplateDecl *PrevAliasTemplate = nullptr;
-  if (Pattern->getPreviousDecl()) {
+  if (getPreviousDeclForInstantiation<TypedefNameDecl>(Pattern)) {
     DeclContext::lookup_result Found = Owner->lookup(Pattern->getDeclName());
     if (!Found.empty()) {
       PrevAliasTemplate = dyn_cast<TypeAliasTemplateDecl>(Found.front());
@@ -714,9 +734,9 @@ Decl *TemplateDeclInstantiator::VisitStaticAssertDecl(StaticAssertDecl *D) {
 
 Decl *TemplateDeclInstantiator::VisitEnumDecl(EnumDecl *D) {
   EnumDecl *PrevDecl = nullptr;
-  if (D->getPreviousDecl()) {
+  if (EnumDecl *PatternPrev = getPreviousDeclForInstantiation(D)) {
     NamedDecl *Prev = SemaRef.FindInstantiatedDecl(D->getLocation(),
-                                                   D->getPreviousDecl(),
+                                                   PatternPrev,
                                                    TemplateArgs);
     if (!Prev) return nullptr;
     PrevDecl = cast<EnumDecl>(Prev);
@@ -878,7 +898,7 @@ Decl *TemplateDeclInstantiator::VisitClassTemplateDecl(ClassTemplateDecl *D) {
   CXXRecordDecl *PrevDecl = nullptr;
   ClassTemplateDecl *PrevClassTemplate = nullptr;
 
-  if (!isFriend && Pattern->getPreviousDecl()) {
+  if (!isFriend && getPreviousDeclForInstantiation(Pattern)) {
     DeclContext::lookup_result Found = Owner->lookup(Pattern->getDeclName());
     if (!Found.empty()) {
       PrevClassTemplate = dyn_cast<ClassTemplateDecl>(Found.front());
@@ -1072,7 +1092,7 @@ Decl *TemplateDeclInstantiator::VisitVarTemplateDecl(VarTemplateDecl *D) {
   VarDecl *Pattern = D->getTemplatedDecl();
   VarTemplateDecl *PrevVarTemplate = nullptr;
 
-  if (Pattern->getPreviousDecl()) {
+  if (getPreviousDeclForInstantiation(Pattern)) {
     DeclContext::lookup_result Found = Owner->lookup(Pattern->getDeclName());
     if (!Found.empty())
       PrevVarTemplate = dyn_cast<VarTemplateDecl>(Found.front());
@@ -1182,7 +1202,7 @@ TemplateDeclInstantiator::VisitFunctionTemplateDecl(FunctionTemplateDecl *D) {
   if (!isFriend) {
     Owner->addDecl(InstTemplate);
   } else if (InstTemplate->getDeclContext()->isRecord() &&
-             !D->getPreviousDecl()) {
+             !getPreviousDeclForInstantiation(D)) {
     SemaRef.CheckFriendAccess(InstTemplate);
   }
 
@@ -1193,9 +1213,9 @@ Decl *TemplateDeclInstantiator::VisitCXXRecordDecl(CXXRecordDecl *D) {
   CXXRecordDecl *PrevDecl = nullptr;
   if (D->isInjectedClassName())
     PrevDecl = cast<CXXRecordDecl>(Owner);
-  else if (D->getPreviousDecl()) {
+  else if (CXXRecordDecl *PatternPrev = getPreviousDeclForInstantiation(D)) {
     NamedDecl *Prev = SemaRef.FindInstantiatedDecl(D->getLocation(),
-                                                   D->getPreviousDecl(),
+                                                   PatternPrev,
                                                    TemplateArgs);
     if (!Prev) return nullptr;
     PrevDecl = cast<CXXRecordDecl>(Prev);
@@ -2259,7 +2279,8 @@ Decl *TemplateDeclInstantiator::VisitUsingDecl(UsingDecl *D) {
     if (CheckRedeclaration) {
       if (SemaRef.CheckUsingShadowDecl(NewUD, InstTarget, Prev, PrevDecl))
         continue;
-    } else if (UsingShadowDecl *OldPrev = Shadow->getPreviousDecl()) {
+    } else if (UsingShadowDecl *OldPrev =
+                   getPreviousDeclForInstantiation(Shadow)) {
       PrevDecl = cast_or_null<UsingShadowDecl>(SemaRef.FindInstantiatedDecl(
           Shadow->getLocation(), OldPrev, TemplateArgs));
     }