1 files changed, 63 insertions, 0 deletions
diff --git a/clang-tools-extra/clang-tidy/misc/MisplacedConstCheck.cpp b/clang-tools-extra/clang-tidy/misc/MisplacedConstCheck.cpp
new file mode 100644
index 00000000000..515b22c0c3e
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/misc/MisplacedConstCheck.cpp
@@ -0,0 +1,63 @@
+//===--- MisplacedConstCheck.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 "MisplacedConstCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+void MisplacedConstCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      valueDecl(hasType(isConstQualified()),
+                hasType(typedefType(hasDeclaration(
+                    typedefDecl(hasType(pointerType(unless(pointee(
+                                    anyOf(isConstQualified(),
+                                          ignoringParens(functionType())))))))
+                        .bind("typedef")))))
+          .bind("decl"),
+      this);
+}
+
+static QualType guessAlternateQualification(ASTContext &Context, QualType QT) {
+  // We're given a QualType from a typedef where the qualifiers apply to the
+  // pointer instead of the pointee. Strip the const qualifier from the pointer
+  // type and add it to the pointee instead.
+  if (!QT->isPointerType())
+    return QT;
+
+  Qualifiers Quals = QT.getLocalQualifiers();
+  Quals.removeConst();
+
+  QualType NewQT = Context.getPointerType(
+      QualType(QT->getPointeeType().getTypePtr(), Qualifiers::Const));
+  return NewQT.withCVRQualifiers(Quals.getCVRQualifiers());
+}
+
+void MisplacedConstCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *Var = Result.Nodes.getNodeAs<ValueDecl>("decl");
+  const auto *Typedef = Result.Nodes.getNodeAs<TypedefDecl>("typedef");
+  ASTContext &Ctx = *Result.Context;
+  QualType CanQT = Var->getType().getCanonicalType();
+
+  diag(Var->getLocation(), "%0 declared with a const-qualified typedef type; "
+                           "results in the type being '%1' instead of '%2'")
+      << Var << CanQT.getAsString(Ctx.getPrintingPolicy())
+      << guessAlternateQualification(Ctx, CanQT)
+             .getAsString(Ctx.getPrintingPolicy());
+  diag(Typedef->getLocation(), "typedef declared here", DiagnosticIDs::Note);
+}
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang