Index: clang/include/clang/AST/DeclBase.h
===================================================================
--- clang/include/clang/AST/DeclBase.h
+++ clang/include/clang/AST/DeclBase.h
@@ -2427,6 +2427,8 @@
                    bool Deserialize = false) const;
 
 private:
+  void addDeclImpl(Decl *D, bool Internal);
+
   /// Whether this declaration context has had externally visible
   /// storage added since the last lookup. In this case, \c LookupPtr's
   /// invariant may not hold and needs to be fixed before we perform
Index: clang/lib/AST/DeclBase.cpp
===================================================================
--- clang/lib/AST/DeclBase.cpp
+++ clang/lib/AST/DeclBase.cpp
@@ -1570,20 +1570,25 @@
   }
 }
 
-void DeclContext::addDecl(Decl *D) {
+void DeclContext::addDeclImpl(Decl *D, bool Internal) {
+  DeclContext *PrimaryContext = nullptr;
+  NamedDecl *ND = nullptr;
+  // Calculate the primary context before adding the decl. Calculating the
+  // primary context might end up unintentionally adding the new decl to the
+  // same lookup we will manually add it at the end of this function.
+  if ((ND = dyn_cast<NamedDecl>(D)))
+    PrimaryContext = ND->getDeclContext()->getPrimaryContext();
+
   addHiddenDecl(D);
 
-  if (auto *ND = dyn_cast<NamedDecl>(D))
-    ND->getDeclContext()->getPrimaryContext()->
-        makeDeclVisibleInContextWithFlags(ND, false, true);
+  if (ND)
+    PrimaryContext->makeDeclVisibleInContextWithFlags(ND, Internal, true);
 }
 
-void DeclContext::addDeclInternal(Decl *D) {
-  addHiddenDecl(D);
+void DeclContext::addDecl(Decl *D) { addDeclImpl(D, /*Internal*/ false); }
 
-  if (auto *ND = dyn_cast<NamedDecl>(D))
-    ND->getDeclContext()->getPrimaryContext()->
-        makeDeclVisibleInContextWithFlags(ND, true, true);
+void DeclContext::addDeclInternal(Decl *D) {
+  addDeclImpl(D, /*Internal*/ true);
 }
 
 /// buildLookup - Build the lookup data structure with all of the