1 files changed, 67 insertions, 0 deletions
diff --git a/clang-tools-extra/clang-tidy/misc/AssignOperatorSignatureCheck.cpp b/clang-tools-extra/clang-tidy/misc/AssignOperatorSignatureCheck.cpp
new file mode 100644
index 00000000000..26255401a65
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/misc/AssignOperatorSignatureCheck.cpp
@@ -0,0 +1,67 @@
+//===--- AssignOperatorSignatureCheck.cpp - clang-tidy ----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AssignOperatorSignatureCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+
+void AssignOperatorSignatureCheck::registerMatchers(
+    ast_matchers::MatchFinder *Finder) {
+  const auto HasGoodReturnType = methodDecl(returns(lValueReferenceType(pointee(
+      unless(isConstQualified()), hasDeclaration(equalsBoundNode("class"))))));
+
+  const auto IsSelf = qualType(
+      anyOf(hasDeclaration(equalsBoundNode("class")),
+            referenceType(pointee(hasDeclaration(equalsBoundNode("class"))))));
+  const auto IsSelfAssign =
+      methodDecl(unless(anyOf(isDeleted(), isPrivate(), isImplicit())),
+                 hasName("operator="), ofClass(recordDecl().bind("class")),
+                 hasParameter(0, parmVarDecl(hasType(IsSelf)))).bind("method");
+
+  Finder->addMatcher(
+      methodDecl(IsSelfAssign, unless(HasGoodReturnType)).bind("ReturnType"),
+      this);
+
+  const auto BadSelf = referenceType(
+      anyOf(lValueReferenceType(pointee(unless(isConstQualified()))),
+            rValueReferenceType(pointee(isConstQualified()))));
+
+  Finder->addMatcher(
+      methodDecl(IsSelfAssign, hasParameter(0, parmVarDecl(hasType(BadSelf))))
+          .bind("ArgumentType"),
+      this);
+
+  Finder->addMatcher(methodDecl(IsSelfAssign, isConst()).bind("Const"), this);
+}
+
+
+void AssignOperatorSignatureCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto* Method = Result.Nodes.getNodeAs<CXXMethodDecl>("method");
+  std::string Name = Method->getParent()->getName();
+
+  static const char *Messages[][2] = {
+      {"ReturnType", "operator=() should return '%0&'"},
+      {"ArgumentType", "operator=() should take '%0 const&', '%0&&' or '%0'"},
+      {"Const", "operator=() should not be marked 'const'"},
+  };
+
+  for (const auto& Message : Messages) {
+    if (Result.Nodes.getNodeAs<Decl>(Message[0]))
+      diag(Method->getLocStart(), Message[1]) << Name;
+  }
+}
+
+} // namespace tidy
+} // namespace clang