Reverted to verified version + NFC

Author: dmpolukhin

clang/lib/Serialization/ASTWriterDecl.cpp

@@ -33,14 +33,10 @@ using namespace serialization;
 
 namespace {
 
-// Helper function that returns dependent decl context for the declaration
-// passed in the argument.
-template <typename DCT> DCT *getDependentDeclContext(Decl *D) {
-  if (auto *DC = llvm::dyn_cast_or_null<DCT>(D->getDeclContext());
-      DC && DC->isDependentContext() && DC->isThisDeclarationADefinition()) {
-    return DC;
-  }
-  return nullptr;
+// Helper function that returns true if the decl passed in the argument is
+// a defintion in dependent contxt.
+template <typename DT> bool isDefinitionInDependentContext(DT *D) {
+  return D->isDependentContext() && D->isThisDeclarationADefinition();
 }
 
 } // namespace
@@ -820,9 +816,11 @@ void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
     // For a friend function defined inline within a class template, we have to
     // force the definition to be the one inside the definition of the template
     // class. Remember this relation to deserialize them together.
-    if (auto *RD = getDependentDeclContext<CXXRecordDecl>(D))
+    if (auto *RD = dyn_cast<CXXRecordDecl>(D->getLexicalParent());
+        isDefinitionInDependentContext(RD)) {
       Writer.RelatedDeclsMap[Writer.GetDeclRef(RD)].push_back(
           Writer.GetDeclRef(D));
+    }
   }
 
   Record.push_back(D->param_size());
@@ -1589,7 +1587,8 @@ void ASTDeclWriter::VisitCXXRecordDecl(CXXRecordDecl *D) {
     }
     // For lambdas inside template functions, remember the mapping to
     // deserialize them together.
-    if (auto *FD = getDependentDeclContext<FunctionDecl>(D)) {
+    if (auto *FD = llvm::dyn_cast_or_null<FunctionDecl>(D->getDeclContext());
+        FD && isDefinitionInDependentContext(FD)) {
       Writer.RelatedDeclsMap[Writer.GetDeclRef(FD)].push_back(
           Writer.GetDeclRef(D));
     }