2 files changed, 32 insertions, 17 deletions
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index 8460030b4b2..35c0f690db8 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -3491,13 +3491,16 @@ Decl *ASTNodeImporter::VisitObjCCategoryDecl(ObjCCategoryDecl *D) {
                                        Importer.Import(D->getCategoryNameLoc()), 
                                           Name.getAsIdentifierInfo(),
                                           ToInterface,
-                                          ImportObjCTypeParamList(
-                                            D->getTypeParamList()),
+                                          /*TypeParamList=*/nullptr,
                                        Importer.Import(D->getIvarLBraceLoc()),
                                        Importer.Import(D->getIvarRBraceLoc()));
     ToCategory->setLexicalDeclContext(LexicalDC);
     LexicalDC->addDeclInternal(ToCategory);
     Importer.Imported(D, ToCategory);
+    // Import the type parameter list after calling Imported, to avoid
+    // loops when bringing in their DeclContext.
+    ToCategory->setTypeParamList(ImportObjCTypeParamList(
+                                   D->getTypeParamList()));
     
     // Import protocols
     SmallVector<ObjCProtocolDecl *, 4> Protocols;
@@ -3819,14 +3822,17 @@ Decl *ASTNodeImporter::VisitObjCInterfaceDecl(ObjCInterfaceDecl *D) {
     ToIface = ObjCInterfaceDecl::Create(Importer.getToContext(), DC,
                                         Importer.Import(D->getAtStartLoc()),
                                         Name.getAsIdentifierInfo(),
-                                        ImportObjCTypeParamList(
-                                          D->getTypeParamListAsWritten()),
+                                        /*TypeParamList=*/nullptr,
                                         /*PrevDecl=*/nullptr, Loc,
                                         D->isImplicitInterfaceDecl());
     ToIface->setLexicalDeclContext(LexicalDC);
     LexicalDC->addDeclInternal(ToIface);
   }
   Importer.Imported(D, ToIface);
+  // Import the type parameter list after calling Imported, to avoid
+  // loops when bringing in their DeclContext.
+  ToIface->setTypeParamList(ImportObjCTypeParamList(
+                              D->getTypeParamListAsWritten()));
   
   if (D->isThisDeclarationADefinition() && ImportDefinition(D, ToIface))
     return nullptr;
diff --git a/clang/lib/AST/DeclObjC.cpp b/clang/lib/AST/DeclObjC.cpp
index da4bc549cf4..b540e37cd07 100644
--- a/clang/lib/AST/DeclObjC.cpp
+++ b/clang/lib/AST/DeclObjC.cpp
@@ -259,6 +259,15 @@ ObjCTypeParamList *ObjCInterfaceDecl::getTypeParamList() const {
   return nullptr;
 }
 
+void ObjCInterfaceDecl::setTypeParamList(ObjCTypeParamList *TPL) {
+  TypeParamList = TPL;
+  if (!TPL)
+    return;
+  // Set the declaration context of each of the type parameters.
+  for (auto typeParam : *TypeParamList)
+    typeParam->setDeclContext(this);
+}
+
 ObjCInterfaceDecl *ObjCInterfaceDecl::getSuperClass() const {
   // FIXME: Should make sure no callers ever do this.
   if (!hasDefinition())
@@ -1302,7 +1311,7 @@ ObjCInterfaceDecl::ObjCInterfaceDecl(const ASTContext &C, DeclContext *DC,
                                      ObjCInterfaceDecl *PrevDecl,
                                      bool IsInternal)
     : ObjCContainerDecl(ObjCInterface, DC, Id, CLoc, AtLoc),
-      redeclarable_base(C), TypeForDecl(nullptr), TypeParamList(typeParamList),
+      redeclarable_base(C), TypeForDecl(nullptr), TypeParamList(nullptr),
       Data() {
   setPreviousDecl(PrevDecl);
   
@@ -1312,11 +1321,7 @@ ObjCInterfaceDecl::ObjCInterfaceDecl(const ASTContext &C, DeclContext *DC,
   
   setImplicit(IsInternal);
 
-  // Update the declaration context of the type parameters.
-  if (typeParamList) {
-    for (auto typeParam : *typeParamList)
-      typeParam->setDeclContext(this);
-  }
+  setTypeParamList(typeParamList);
 }
 
 void ObjCInterfaceDecl::LoadExternalDefinition() const {
@@ -1799,16 +1804,11 @@ ObjCCategoryDecl::ObjCCategoryDecl(DeclContext *DC, SourceLocation AtLoc,
                                    SourceLocation IvarLBraceLoc,
                                    SourceLocation IvarRBraceLoc)
   : ObjCContainerDecl(ObjCCategory, DC, Id, ClassNameLoc, AtLoc),
-    ClassInterface(IDecl), TypeParamList(typeParamList),
+    ClassInterface(IDecl), TypeParamList(nullptr),
     NextClassCategory(nullptr), CategoryNameLoc(CategoryNameLoc),
     IvarLBraceLoc(IvarLBraceLoc), IvarRBraceLoc(IvarRBraceLoc) 
 {
-  // Set the declaration context of each of the type parameters.
-  if (typeParamList) {
-    for (auto typeParam : *typeParamList) {
-      typeParam->setDeclContext(this);
-    }
-  }
+  setTypeParamList(typeParamList);
 }
 
 ObjCCategoryDecl *ObjCCategoryDecl::Create(ASTContext &C, DeclContext *DC,
@@ -1853,6 +1853,15 @@ void ObjCCategoryDecl::setImplementation(ObjCCategoryImplDecl *ImplD) {
   getASTContext().setObjCImplementation(this, ImplD);
 }
 
+void ObjCCategoryDecl::setTypeParamList(ObjCTypeParamList *TPL) {
+  TypeParamList = TPL;
+  if (!TPL)
+    return;
+  // Set the declaration context of each of the type parameters.
+  for (auto typeParam : *TypeParamList)
+    typeParam->setDeclContext(this);
+}
+
 
 //===----------------------------------------------------------------------===//
 // ObjCCategoryImplDecl