Index: clang/lib/Sema/SemaDeclCXX.cpp
===================================================================
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -16595,7 +16595,8 @@
   bool AddToScope = true;
   NamedDecl *ND = ActOnFunctionDeclarator(DCScope, D, DC, TInfo, Previous,
                                           TemplateParams, AddToScope);
-  if (!ND) return nullptr;
+  if (!ND || ND->isInvalidDecl())
+    return nullptr;
 
   assert(ND->getLexicalDeclContext() == CurContext);
 
Index: clang/test/CodeGenCXX/invalid-decl.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/invalid-decl.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -emit-llvm %s -verify
+class test1 {
+  template <typename> friend int bar(bool = true) { // expected-note {{previous declaration is here}}
+    return 1;
+  }
+  template <typename> friend int bar(bool); // expected-error {{friend declaration specifying a default argument must be the only declaration}}
+};
+
+class test2 {
+  friend int bar(bool = true) // expected-note {{previous declaration is here}}
+  {
+    return 1;
+  }
+  friend int bar(bool); // expected-error {{friend declaration specifying a default argument must be the only declaration}}
+};