--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang-tools-extra/clang-tidy/utils/TransformerClangTidyCheck.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,113 @@
+//===---------- TransformerClangTidyCheck.cpp - clang-tidy ----------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "TransformerClangTidyCheck.h"
+#include "llvm/ADT/STLExtras.h"
+
+namespace clang {
+namespace tidy {
+namespace utils {
+using transformer::RewriteRule;
+
+#ifndef NDEBUG
+static bool hasExplanation(const RewriteRule::Case &C) {
+  return C.Explanation != nullptr;
+}
+#endif
+
+// This constructor cannot dispatch to the simpler one (below), because, in
+// order to get meaningful results from `getLangOpts` and `Options`, we need the
+// `ClangTidyCheck()` constructor to have been called. If we were to dispatch,
+// we would be accessing `getLangOpts` and `Options` before the underlying
+// `ClangTidyCheck` instance was properly initialized.
+TransformerClangTidyCheck::TransformerClangTidyCheck(
+    std::function<Optional<RewriteRule>(const LangOptions &,
+                                        const OptionsView &)>
+        MakeRule,
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context), Rule(MakeRule(getLangOpts(), Options)) {
+  if (Rule)
+    assert(llvm::all_of(Rule->Cases, hasExplanation) &&
+           "clang-tidy checks must have an explanation by default;"
+           " explicitly provide an empty explanation if none is desired");
+}
+
+TransformerClangTidyCheck::TransformerClangTidyCheck(RewriteRule R,
+                                                     StringRef Name,
+                                                     ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context), Rule(std::move(R)) {
+  assert(llvm::all_of(Rule->Cases, hasExplanation) &&
+         "clang-tidy checks must have an explanation by default;"
+         " explicitly provide an empty explanation if none is desired");
+}
+
+void TransformerClangTidyCheck::registerPPCallbacks(
+    const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
+  // Only allocate and register the IncludeInsert when some `Case` will add
+  // includes.
+  if (Rule && llvm::any_of(Rule->Cases, [](const RewriteRule::Case &C) {
+        return !C.AddedIncludes.empty();
+      })) {
+    Inserter = std::make_unique<IncludeInserter>(
+        SM, getLangOpts(), utils::IncludeSorter::IS_LLVM);
+    PP->addPPCallbacks(Inserter->CreatePPCallbacks());
+  }
+}
+
+void TransformerClangTidyCheck::registerMatchers(
+    ast_matchers::MatchFinder *Finder) {
+  if (Rule)
+    for (auto &Matcher : transformer::detail::buildMatchers(*Rule))
+      Finder->addDynamicMatcher(Matcher, this);
+}
+
+void TransformerClangTidyCheck::check(
+    const ast_matchers::MatchFinder::MatchResult &Result) {
+  if (Result.Context->getDiagnostics().hasErrorOccurred())
+    return;
+
+  assert(Rule && "check() should not fire if Rule is None");
+  RewriteRule::Case Case = transformer::detail::findSelectedCase(Result, *Rule);
+  Expected<SmallVector<transformer::detail::Transformation, 1>>
+      Transformations = transformer::detail::translateEdits(Result, Case.Edits);
+  if (!Transformations) {
+    llvm::errs() << "Rewrite failed: "
+                 << llvm::toString(Transformations.takeError()) << "\n";
+    return;
+  }
+
+  // No rewrite applied, but no error encountered either.
+  if (Transformations->empty())
+    return;
+
+  Expected<std::string> Explanation = Case.Explanation->eval(Result);
+  if (!Explanation) {
+    llvm::errs() << "Error in explanation: "
+                 << llvm::toString(Explanation.takeError()) << "\n";
+    return;
+  }
+
+  // Associate the diagnostic with the location of the first change.
+  DiagnosticBuilder Diag =
+      diag((*Transformations)[0].Range.getBegin(), *Explanation);
+  for (const auto &T : *Transformations)
+    Diag << FixItHint::CreateReplacement(T.Range, T.Replacement);
+
+  for (const auto &I : Case.AddedIncludes) {
+    auto &Header = I.first;
+    if (Optional<FixItHint> Fix = Inserter->CreateIncludeInsertion(
+            Result.SourceManager->getMainFileID(), Header,
+            /*IsAngled=*/I.second == transformer::IncludeFormat::Angled)) {
+      Diag << *Fix;
+    }
+  }
+}
+
+} // namespace utils
+} // namespace tidy
+} // namespace clang