Index: include/llvm/Support/YAMLTraits.h
===================================================================
--- include/llvm/Support/YAMLTraits.h
+++ include/llvm/Support/YAMLTraits.h
@@ -976,6 +976,10 @@
         void *Ctxt = nullptr,
         SourceMgr::DiagHandlerTy DiagHandler = nullptr,
         void *DiagHandlerCtxt = nullptr);
+  Input(MemoryBuffer& 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: lib/Support/YAMLTraits.cpp
===================================================================
--- lib/Support/YAMLTraits.cpp
+++ lib/Support/YAMLTraits.cpp
@@ -56,6 +56,19 @@
   DocIterator = Strm->begin();
 }
 
+Input::Input(MemoryBuffer& Input,
+             void *Ctxt,
+             SourceMgr::DiagHandlerTy DiagHandler,
+             void *DiagHandlerCtxt)
+  : IO(Ctxt),
+    Strm(new Stream(
+      MemoryBufferRef(Input.getBuffer(), Input.getBufferIdentifier()), SrcMgr)),
+    CurrentNode(nullptr) {
+  if (DiagHandler)
+    SrcMgr.setDiagHandler(DiagHandler, DiagHandlerCtxt);
+  DocIterator = Strm->begin();
+}
+
 Input::~Input() {
 }