diff --git a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
new file mode 100644
index 0000000..90ac67b
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
@@ -0,0 +1,471 @@
+//===--- UseNullptrCheck.cpp - clang-tidy----------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "UseNullptrCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+#include "llvm/ADT/StringExtras.h"
+
+using namespace clang;
+using namespace clang::ast_matchers;
+using namespace llvm;
+
+namespace clang {
+namespace tidy {
+namespace modernize {
+
+const char CastSequence[] = "sequence";
+
+/// \brief Matches cast expressions that have a cast kind of CK_NullToPointer
+/// or CK_NullToMemberPointer.
+///
+/// Given
+/// \code
+///   int *p = 0;
+/// \endcode
+/// implicitCastExpr(isNullToPointer()) matches the implicit cast clang adds
+/// around \c 0.
+AST_MATCHER(CastExpr, isNullToPointer) {
+  return Node.getCastKind() == CK_NullToPointer ||
+         Node.getCastKind() == CK_NullToMemberPointer;
+}
+
+AST_MATCHER(Type, sugaredNullptrType) {
+  const Type *DesugaredType = Node.getUnqualifiedDesugaredType();
+  if (const BuiltinType *BT = dyn_cast<BuiltinType>(DesugaredType))
+    return BT->getKind() == BuiltinType::NullPtr;
+  return false;
+}
+
+/// \brief Create a matcher that finds implicit casts as well as the head of a
+/// sequence of zero or more nested explicit casts that have an implicit cast
+/// to null within.
+/// Finding sequences of explict casts is necessary so that an entire sequence
+/// can be replaced instead of just the inner-most implicit cast.
+StatementMatcher makeCastSequenceMatcher() {
+  StatementMatcher ImplicitCastToNull = implicitCastExpr(
+      isNullToPointer(),
+      unless(hasSourceExpression(hasType(sugaredNullptrType()))));
+
+  return castExpr(anyOf(ImplicitCastToNull,
+                        explicitCastExpr(hasDescendant(ImplicitCastToNull))),
+                  unless(hasAncestor(explicitCastExpr())))
+      .bind(CastSequence);
+}
+
+bool isReplaceableRange(SourceLocation StartLoc, SourceLocation EndLoc,
+                        const SourceManager &SM) {
+  return SM.isWrittenInSameFile(StartLoc, EndLoc);
+}
+
+/// \brief Replaces the provided range with the text "nullptr", but only if
+/// the start and end location are both in main file.
+/// Returns true if and only if a replacement was made.
+void replaceWithNullptr(ClangTidyCheck &Check, SourceManager &SM,
+                        SourceLocation StartLoc, SourceLocation EndLoc) {
+  CharSourceRange Range(SourceRange(StartLoc, EndLoc), true);
+  // Add a space if nullptr follows an alphanumeric character. This happens
+  // whenever there is an c-style explicit cast to nullptr not surrounded by
+  // parentheses and right beside a return statement.
+  SourceLocation PreviousLocation = StartLoc.getLocWithOffset(-1);
+  bool NeedsSpace = isAlphanumeric(*SM.getCharacterData(PreviousLocation));
+  Check.diag(Range.getBegin(), "use nullptr") << FixItHint::CreateReplacement(
+      Range, NeedsSpace ? " nullptr" : "nullptr");
+}
+
+/// \brief Returns the name of the outermost macro.
+///
+/// Given
+/// \code
+/// #define MY_NULL NULL
+/// \endcode
+/// If \p Loc points to NULL, this function will return the name MY_NULL.
+StringRef getOutermostMacroName(SourceLocation Loc, const SourceManager &SM,
+                                const LangOptions &LO) {
+  assert(Loc.isMacroID());
+  SourceLocation OutermostMacroLoc;
+
+  while (Loc.isMacroID()) {
+    OutermostMacroLoc = Loc;
+    Loc = SM.getImmediateMacroCallerLoc(Loc);
+  }
+
+  return Lexer::getImmediateMacroName(OutermostMacroLoc, SM, LO);
+}
+
+/// \brief RecursiveASTVisitor for ensuring all nodes rooted at a given AST
+/// subtree that have file-level source locations corresponding to a macro
+/// argument have implicit NullTo(Member)Pointer nodes as ancestors.
+class MacroArgUsageVisitor : public RecursiveASTVisitor<MacroArgUsageVisitor> {
+public:
+  MacroArgUsageVisitor(SourceLocation CastLoc, const SourceManager &SM)
+      : CastLoc(CastLoc), SM(SM), Visited(false), CastFound(false),
+        InvalidFound(false) {
+    assert(CastLoc.isFileID());
+  }
+
+  bool TraverseStmt(Stmt *S) {
+    bool VisitedPreviously = Visited;
+
+    if (!RecursiveASTVisitor<MacroArgUsageVisitor>::TraverseStmt(S))
+      return false;
+
+    // The point at which VisitedPreviously is false and Visited is true is the
+    // root of a subtree containing nodes whose locations match CastLoc. It's
+    // at this point we test that the Implicit NullTo(Member)Pointer cast was
+    // found or not.
+    if (!VisitedPreviously) {
+      if (Visited && !CastFound) {
+        // Found nodes with matching SourceLocations but didn't come across a
+        // cast. This is an invalid macro arg use. Can stop traversal
+        // completely now.
+        InvalidFound = true;
+        return false;
+      }
+      // Reset state as we unwind back up the tree.
+      CastFound = false;
+      Visited = false;
+    }
+    return true;
+  }
+
+  bool VisitStmt(Stmt *S) {
+    if (SM.getFileLoc(S->getLocStart()) != CastLoc)
+      return true;
+    Visited = true;
+
+    const ImplicitCastExpr *Cast = dyn_cast<ImplicitCastExpr>(S);
+    if (Cast && (Cast->getCastKind() == CK_NullToPointer ||
+                 Cast->getCastKind() == CK_NullToMemberPointer))
+      CastFound = true;
+
+    return true;
+  }
+
+  bool foundInvalid() const { return InvalidFound; }
+
+private:
+  SourceLocation CastLoc;
+  const SourceManager &SM;
+
+  bool Visited;
+  bool CastFound;
+  bool InvalidFound;
+};
+
+/// \brief Looks for implicit casts as well as sequences of 0 or more explicit
+/// casts with an implicit null-to-pointer cast within.
+///
+/// The matcher this visitor is used with will find a single implicit cast or a
+/// top-most explicit cast (i.e. it has no explicit casts as an ancestor) where
+/// an implicit cast is nested within. However, there is no guarantee that only
+/// explicit casts exist between the found top-most explicit cast and the
+/// possibly more than one nested implicit cast. This visitor finds all cast
+/// sequences with an implicit cast to null within and creates a replacement
+/// leaving the outermost explicit cast unchanged to avoid introducing
+/// ambiguities.
+class CastSequenceVisitor : public RecursiveASTVisitor<CastSequenceVisitor> {
+public:
+  CastSequenceVisitor(ASTContext &Context, ArrayRef<StringRef> NullMacros,
+                      ClangTidyCheck &check)
+      : SM(Context.getSourceManager()), Context(Context),
+        NullMacros(NullMacros), Check(check), FirstSubExpr(nullptr),
+        PruneSubtree(false) {}
+
+  bool TraverseStmt(Stmt *S) {
+    // Stop traversing down the tree if requested.
+    if (PruneSubtree) {
+      PruneSubtree = false;
+      return true;
+    }
+    return RecursiveASTVisitor<CastSequenceVisitor>::TraverseStmt(S);
+  }
+
+  // Only VisitStmt is overridden as we shouldn't find other base AST types
+  // within a cast expression.
+  bool VisitStmt(Stmt *S) {
+    CastExpr *C = dyn_cast<CastExpr>(S);
+    if (!C) {
+      FirstSubExpr = nullptr;
+      return true;
+    }
+    if (!FirstSubExpr)
+      FirstSubExpr = C->getSubExpr()->IgnoreParens();
+
+    if (C->getCastKind() != CK_NullToPointer &&
+        C->getCastKind() != CK_NullToMemberPointer) {
+      return true;
+    }
+
+    SourceLocation StartLoc = FirstSubExpr->getLocStart();
+    SourceLocation EndLoc = FirstSubExpr->getLocEnd();
+
+    // If the location comes from a macro arg expansion, *all* uses of that
+    // arg must be checked to result in NullTo(Member)Pointer casts.
+    //
+    // If the location comes from a macro body expansion, check to see if its
+    // coming from one of the allowed 'NULL' macros.
+    if (SM.isMacroArgExpansion(StartLoc) && SM.isMacroArgExpansion(EndLoc)) {
+      SourceLocation FileLocStart = SM.getFileLoc(StartLoc),
+                     FileLocEnd = SM.getFileLoc(EndLoc);
+      if (isReplaceableRange(FileLocStart, FileLocEnd, SM) &&
+          allArgUsesValid(C)) {
+        replaceWithNullptr(Check, SM, FileLocStart, FileLocEnd);
+      }
+      return skipSubTree();
+    }
+
+    if (SM.isMacroBodyExpansion(StartLoc) && SM.isMacroBodyExpansion(EndLoc)) {
+      StringRef OutermostMacroName =
+          getOutermostMacroName(StartLoc, SM, Context.getLangOpts());
+
+      // Check to see if the user wants to replace the macro being expanded.
+      if (std::find(NullMacros.begin(), NullMacros.end(), OutermostMacroName) ==
+          NullMacros.end()) {
+        return skipSubTree();
+      }
+
+      StartLoc = SM.getFileLoc(StartLoc);
+      EndLoc = SM.getFileLoc(EndLoc);
+    }
+
+    if (!isReplaceableRange(StartLoc, EndLoc, SM)) {
+      return skipSubTree();
+    }
+    replaceWithNullptr(Check, SM, StartLoc, EndLoc);
+
+    return skipSubTree();
+  }
+
+private:
+  bool skipSubTree() {
+    PruneSubtree = true;
+    return true;
+  }
+
+  /// \brief Tests that all expansions of a macro arg, one of which expands to
+  /// result in \p CE, yield NullTo(Member)Pointer casts.
+  bool allArgUsesValid(const CastExpr *CE) {
+    SourceLocation CastLoc = CE->getLocStart();
+
+    // Step 1: Get location of macro arg and location of the macro the arg was
+    // provided to.
+    SourceLocation ArgLoc, MacroLoc;
+    if (!getMacroAndArgLocations(CastLoc, ArgLoc, MacroLoc))
+      return false;
+
+    // Step 2: Find the first ancestor that doesn't expand from this macro.
+    ast_type_traits::DynTypedNode ContainingAncestor;
+    if (!findContainingAncestor(
+            ast_type_traits::DynTypedNode::create<Stmt>(*CE), MacroLoc,
+            ContainingAncestor))
+      return false;
+
+    // Step 3:
+    // Visit children of this containing parent looking for the least-descended
+    // nodes of the containing parent which are macro arg expansions that expand
+    // from the given arg location.
+    // Visitor needs: arg loc
+    MacroArgUsageVisitor ArgUsageVisitor(SM.getFileLoc(CastLoc), SM);
+    if (const auto *D = ContainingAncestor.get<Decl>())
+      ArgUsageVisitor.TraverseDecl(const_cast<Decl *>(D));
+    else if (const auto *S = ContainingAncestor.get<Stmt>())
+      ArgUsageVisitor.TraverseStmt(const_cast<Stmt *>(S));
+    else
+      llvm_unreachable("Unhandled ContainingAncestor node type");
+
+    return !ArgUsageVisitor.foundInvalid();
+  }
+
+  /// \brief Given the SourceLocation for a macro arg expansion, finds the
+  /// non-macro SourceLocation of the macro the arg was passed to and the
+  /// non-macro SourceLocation of the argument in the arg list to that macro.
+  /// These results are returned via \c MacroLoc and \c ArgLoc respectively.
+  /// These values are undefined if the return value is false.
+  ///
+  /// \returns false if one of the returned SourceLocations would be a
+  /// SourceLocation pointing within the definition of another macro.
+  bool getMacroAndArgLocations(SourceLocation Loc, SourceLocation &ArgLoc,
+                               SourceLocation &MacroLoc) {
+    assert(Loc.isMacroID() && "Only reasonble to call this on macros");
+
+    ArgLoc = Loc;
+
+    // Find the location of the immediate macro expansion.
+    while (true) {
+      std::pair<FileID, unsigned> LocInfo = SM.getDecomposedLoc(ArgLoc);
+      const SrcMgr::SLocEntry *E = &SM.getSLocEntry(LocInfo.first);
+      const SrcMgr::ExpansionInfo &Expansion = E->getExpansion();
+
+      SourceLocation OldArgLoc = ArgLoc;
+      ArgLoc = Expansion.getExpansionLocStart();
+      if (!Expansion.isMacroArgExpansion()) {
+        if (!MacroLoc.isFileID())
+          return false;
+
+        StringRef Name =
+            Lexer::getImmediateMacroName(OldArgLoc, SM, Context.getLangOpts());
+        return std::find(NullMacros.begin(), NullMacros.end(), Name) !=
+               NullMacros.end();
+      }
+
+      MacroLoc = SM.getImmediateExpansionRange(ArgLoc).first;
+
+      ArgLoc = Expansion.getSpellingLoc().getLocWithOffset(LocInfo.second);
+      if (ArgLoc.isFileID())
+        return true;
+
+      // If spelling location resides in the same FileID as macro expansion
+      // location, it means there is no inner macro.
+      FileID MacroFID = SM.getFileID(MacroLoc);
+      if (SM.isInFileID(ArgLoc, MacroFID)) {
+        // Don't transform this case. If the characters that caused the
+        // null-conversion come from within a macro, they can't be changed.
+        return false;
+      }
+    }
+
+    llvm_unreachable("getMacroAndArgLocations");
+  }
+
+  /// \brief Tests if TestMacroLoc is found while recursively unravelling
+  /// expansions starting at TestLoc. TestMacroLoc.isFileID() must be true.
+  /// Implementation is very similar to getMacroAndArgLocations() except in this
+  /// case, it's not assumed that TestLoc is expanded from a macro argument.
+  /// While unravelling expansions macro arguments are handled as with
+  /// getMacroAndArgLocations() but in this function macro body expansions are
+  /// also handled.
+  ///
+  /// False means either:
+  /// - TestLoc is not from a macro expansion
+  /// - TestLoc is from a different macro expansion
+  bool expandsFrom(SourceLocation TestLoc, SourceLocation TestMacroLoc) {
+    if (TestLoc.isFileID()) {
+      return false;
+    }
+
+    SourceLocation Loc = TestLoc, MacroLoc;
+
+    while (true) {
+      std::pair<FileID, unsigned> LocInfo = SM.getDecomposedLoc(Loc);
+      const SrcMgr::SLocEntry *E = &SM.getSLocEntry(LocInfo.first);
+      const SrcMgr::ExpansionInfo &Expansion = E->getExpansion();
+
+      Loc = Expansion.getExpansionLocStart();
+
+      if (!Expansion.isMacroArgExpansion()) {
+        if (Loc.isFileID()) {
+          return Loc == TestMacroLoc;
+        }
+        // Since Loc is still a macro ID and it's not an argument expansion, we
+        // don't need to do the work of handling an argument expansion. Simply
+        // keep recursively expanding until we hit a FileID or a macro arg
+        // expansion or a macro arg expansion.
+        continue;
+      }
+
+      MacroLoc = SM.getImmediateExpansionRange(Loc).first;
+      if (MacroLoc.isFileID() && MacroLoc == TestMacroLoc) {
+        // Match made.
+        return true;
+      }
+
+      Loc = Expansion.getSpellingLoc().getLocWithOffset(LocInfo.second);
+      if (Loc.isFileID()) {
+        // If we made it this far without finding a match, there is no match to
+        // be made.
+        return false;
+      }
+    }
+
+    llvm_unreachable("expandsFrom");
+  }
+
+  /// \brief Given a starting point \c Start in the AST, find an ancestor that
+  /// doesn't expand from the macro called at file location \c MacroLoc.
+  ///
+  /// \pre MacroLoc.isFileID()
+  /// \returns true if such an ancestor was found, false otherwise.
+  bool findContainingAncestor(ast_type_traits::DynTypedNode Start,
+                              SourceLocation MacroLoc,
+                              ast_type_traits::DynTypedNode &Result) {
+    // Below we're only following the first parent back up the AST. This should
+    // be fine since for the statements we care about there should only be one
+    // parent as far up as we care. If this assumption doesn't hold, need to
+    // revisit what to do here.
+
+    assert(MacroLoc.isFileID());
+
+    while (true) {
+      const auto &Parents = Context.getParents(Start);
+      if (Parents.empty())
+        return false;
+      assert(Parents.size() == 1 &&
+             "Found an ancestor with more than one parent!");
+
+      const ast_type_traits::DynTypedNode &Parent = Parents[0];
+
+      SourceLocation Loc;
+      if (const auto *D = Parent.get<Decl>())
+        Loc = D->getLocStart();
+      else if (const auto *S = Parent.get<Stmt>())
+        Loc = S->getLocStart();
+      else
+        llvm_unreachable("Expected to find Decl or Stmt containing ancestor");
+
+      if (!expandsFrom(Loc, MacroLoc)) {
+        Result = Parent;
+        return true;
+      }
+      Start = Parent;
+    }
+
+    llvm_unreachable("findContainingAncestor");
+  }
+
+private:
+  SourceManager &SM;
+  ASTContext &Context;
+  ArrayRef<StringRef> NullMacros;
+  ClangTidyCheck &Check;
+  Expr *FirstSubExpr;
+  bool PruneSubtree;
+};
+
+UseNullptrCheck::UseNullptrCheck(StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context) {
+  StringRef MacrosStr = Options.get("NullMacros", "");
+  MacrosStr.split(NullMacros, ",");
+}
+
+void UseNullptrCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "NullMacros",
+                llvm::join(NullMacros.begin(), NullMacros.end(), ","));
+}
+
+void UseNullptrCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(makeCastSequenceMatcher(), this);
+}
+
+void UseNullptrCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *NullCast = Result.Nodes.getNodeAs<CastExpr>(CastSequence);
+  assert(NullCast && "Bad Callback. No node provided");
+
+  // Given an implicit null-ptr cast or an explicit cast with an implicit
+  // null-to-pointer cast within use CastSequenceVisitor to identify sequences
+  // of explicit casts that can be converted into 'nullptr'.
+  CastSequenceVisitor(*Result.Context, NullMacros, *this)
+      .TraverseStmt(const_cast<CastExpr *>(NullCast));
+}
+
+} // namespace modernize
+} // namespace tidy
+} // namespace clang