diff --git a/clang/include/clang/Basic/Specifiers.h b/clang/include/clang/Basic/Specifiers.h
--- a/clang/include/clang/Basic/Specifiers.h
+++ b/clang/include/clang/Basic/Specifiers.h
@@ -19,6 +19,9 @@
 #include "llvm/Support/DataTypes.h"
 #include "llvm/Support/ErrorHandling.h"
 
+namespace llvm {
+class raw_ostream;
+} // namespace llvm
 namespace clang {
 
   /// Define the meaning of possible values of the kind in ExplicitSpecifier.
@@ -333,6 +336,8 @@
     // parameters are assumed to only get null on error.
     NullableResult,
   };
+  /// Prints human-readable debug representation.
+  llvm::raw_ostream &operator<<(llvm::raw_ostream&, NullabilityKind);
 
   /// Return true if \p L has a weaker nullability annotation than \p R. The
   /// ordering is: Unspecified < Nullable < NonNull.
diff --git a/clang/lib/Basic/IdentifierTable.cpp b/clang/lib/Basic/IdentifierTable.cpp
--- a/clang/lib/Basic/IdentifierTable.cpp
+++ b/clang/lib/Basic/IdentifierTable.cpp
@@ -849,6 +849,20 @@
   llvm_unreachable("Unknown nullability kind.");
 }
 
+llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, NullabilityKind NK) {
+  switch (NK) {
+  case NullabilityKind::NonNull:
+    return OS << "NonNull";
+  case NullabilityKind::Nullable:
+    return OS << "Nullable";
+  case NullabilityKind::NullableResult:
+    return OS << "NullableResult";
+  case NullabilityKind::Unspecified:
+    return OS << "Unspecified";
+  }
+  llvm_unreachable("Unknown nullability kind.");
+}
+
 diag::kind
 IdentifierTable::getFutureCompatDiagKind(const IdentifierInfo &II,
                                          const LangOptions &LangOpts) {