--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang-tools-extra/clang-tidy/fuchsia/DefaultArgumentsDeclarationsCheck.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,54 @@
+//===--- DefaultArgumentsDeclarationsCheck.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 "DefaultArgumentsDeclarationsCheck.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace fuchsia {
+
+void DefaultArgumentsDeclarationsCheck::registerMatchers(MatchFinder *Finder) {
+  // Declaring default parameters is disallowed.
+  Finder->addMatcher(parmVarDecl(hasDefaultArgument()).bind("decl"), this);
+}
+
+void DefaultArgumentsDeclarationsCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *D = Result.Nodes.getNodeAs<ParmVarDecl>("decl");
+  if (!D)
+    return;
+
+  SourceRange DefaultArgRange = D->getDefaultArgRange();
+
+  if (DefaultArgRange.getEnd() != D->getEndLoc())
+    return;
+
+  if (DefaultArgRange.getBegin().isMacroID()) {
+    diag(D->getBeginLoc(),
+         "declaring a parameter with a default argument is disallowed");
+    return;
+  }
+
+  SourceLocation StartLocation =
+      D->getName().empty() ? D->getBeginLoc() : D->getLocation();
+
+  SourceRange RemovalRange(
+      Lexer::getLocForEndOfToken(StartLocation, 0, *Result.SourceManager,
+                                 Result.Context->getLangOpts()),
+      DefaultArgRange.getEnd());
+
+  diag(D->getBeginLoc(),
+       "declaring a parameter with a default argument is disallowed")
+      << D << FixItHint::CreateRemoval(RemovalRange);
+}
+
+} // namespace fuchsia
+} // namespace tidy
+} // namespace clang