Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -99,6 +99,7 @@
 def DeleteIncomplete : DiagGroup<"delete-incomplete">;
 def DeleteNonVirtualDtor : DiagGroup<"delete-non-virtual-dtor">;
 def AbstractFinalClass : DiagGroup<"abstract-final-class">;
+def AggregateCtors : DiagGroup<"aggregate-ctors">;
 
 def CXX11CompatDeprecatedWritableStr :
   DiagGroup<"c++11-compat-deprecated-writable-strings">;
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -6466,6 +6466,9 @@
 def warn_jump_out_of_seh_finally : Warning<
   "jump out of __finally block has undefined behavior">,
   InGroup<DiagGroup<"jump-seh-finally">>;
+def warn_aggregate_with_user_declared_constructor : Warning<
+  "aggregate type has user-declared constructors">,
+  InGroup<AggregateCtors>;
 def warn_non_virtual_dtor : Warning<
   "%0 has virtual functions but non-virtual destructor">,
   InGroup<NonVirtualDtor>, DefaultIgnore;
Index: lib/Sema/SemaDeclCXX.cpp
===================================================================
--- lib/Sema/SemaDeclCXX.cpp
+++ lib/Sema/SemaDeclCXX.cpp
@@ -5907,6 +5907,10 @@
            diag::warn_non_virtual_dtor) << Context.getRecordType(Record);
   }
 
+  if (Record->isAggregate() && Record->hasUserDeclaredConstructor()) {
+    Diag(Record->getLocation(), diag::warn_aggregate_with_user_declared_constructor);
+  }
+
   if (Record->isAbstract()) {
     if (FinalAttr *FA = Record->getAttr<FinalAttr>()) {
       Diag(Record->getLocation(), diag::warn_abstract_final_class)