Index: llvm/trunk/include/llvm/Support/YAMLTraits.h
===================================================================
--- llvm/trunk/include/llvm/Support/YAMLTraits.h
+++ llvm/trunk/include/llvm/Support/YAMLTraits.h
@@ -1114,6 +1114,10 @@
         void *Ctxt = nullptr,
         SourceMgr::DiagHandlerTy DiagHandler = nullptr,
         void *DiagHandlerCtxt = nullptr);
+  Input(MemoryBufferRef Input,
+        void *Ctxt = nullptr,
+        SourceMgr::DiagHandlerTy DiagHandler = nullptr,
+        void *DiagHandlerCtxt = nullptr);
   ~Input() override;
 
   // Check if there was an syntax or semantic error during parsing.
Index: llvm/trunk/lib/Support/YAMLTraits.cpp
===================================================================
--- llvm/trunk/lib/Support/YAMLTraits.cpp
+++ llvm/trunk/lib/Support/YAMLTraits.cpp
@@ -60,6 +60,14 @@
   DocIterator = Strm->begin();
 }
 
+Input::Input(MemoryBufferRef Input, void *Ctxt,
+             SourceMgr::DiagHandlerTy DiagHandler, void *DiagHandlerCtxt)
+    : IO(Ctxt), Strm(new Stream(Input, SrcMgr, false, &EC)) {
+  if (DiagHandler)
+    SrcMgr.setDiagHandler(DiagHandler, DiagHandlerCtxt);
+  DocIterator = Strm->begin();
+}
+
 Input::~Input() = default;
 
 std::error_code Input::error() { return EC; }
Index: llvm/trunk/unittests/Support/YAMLIOTest.cpp
===================================================================
--- llvm/trunk/unittests/Support/YAMLIOTest.cpp
+++ llvm/trunk/unittests/Support/YAMLIOTest.cpp
@@ -232,6 +232,22 @@
   }
 }
 
+//
+// Test YAML filename handling.
+//
+static void testErrorFilename(const llvm::SMDiagnostic &Error, void *) {
+  EXPECT_EQ(Error.getFilename(), "foo.yaml");
+}
+
+TEST(YAMLIO, TestGivenFilename) {
+  auto Buffer = llvm::MemoryBuffer::getMemBuffer("{ x: 42 }", "foo.yaml");
+  Input yin(*Buffer, nullptr, testErrorFilename);
+  FooBar Value;
+  yin >> Value;
+
+  EXPECT_TRUE(!!yin.error());
+}
+
 
 //===----------------------------------------------------------------------===//
 //  Test built-in types