Index: clang/lib/AST/ItaniumMangle.cpp
===================================================================
--- clang/lib/AST/ItaniumMangle.cpp
+++ clang/lib/AST/ItaniumMangle.cpp
@@ -2338,7 +2338,8 @@
     return true;
   if (Ty->isBuiltinType())
     return false;
-
+  if (isa<AutoType>(Ty))
+    return false;
   return true;
 }
 
@@ -3250,14 +3251,13 @@
 }
 
 void CXXNameMangler::mangleType(const AutoType *T) {
-  QualType D = T->getDeducedType();
-  // <builtin-type> ::= Da  # dependent auto
-  if (D.isNull()) {
-    assert(T->getKeyword() != AutoTypeKeyword::GNUAutoType &&
-           "shouldn't need to mangle __auto_type!");
-    Out << (T->isDecltypeAuto() ? "Dc" : "Da");
-  } else
-    mangleType(D);
+  assert(T->getDeducedType().isNull() &&
+         "Deduced AutoType shouldn't be handled here!");
+  assert(T->getKeyword() != AutoTypeKeyword::GNUAutoType &&
+         "shouldn't need to mangle __auto_type!");
+  // <builtin-type> ::= Da # auto
+  //                ::= Dc # decltype(auto)
+  Out << (T->isDecltypeAuto() ? "Dc" : "Da");
 }
 
 void CXXNameMangler::mangleType(const DeducedTemplateSpecializationType *T) {
Index: clang/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
===================================================================
--- clang/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
+++ clang/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
@@ -52,10 +52,10 @@
   
   template<class T> auto foo() { return [](const T&) { return 42; }; }
 };
-//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIdE14default_lambdaIdEEDavENKUlRKdE_clES5_(%class.anon
+//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIdE14default_lambdaIdEEDavENKUlRKdE_clES4_(%class.anon
 int run2 = A<double>{}.func()(3.14);
 
-//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIcE14default_lambdaIcEEDavENKUlRKcE_clES5_(%class.anon
+//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIcE14default_lambdaIcEEDavENKUlRKcE_clES4_(%class.anon
 int run3 = A<char>{}.func()('a');
 } // end inline_member_function