================
@@ -0,0 +1,101 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "UseAsConstCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+namespace {
+
+AST_MATCHER(Expr, isLValueExpr) { return Node.isLValue(); }
+
+AST_MATCHER_P(ExplicitCastExpr, hasSourceExpressionAsWritten,
+              ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
+  const Expr *Sub = Node.getSubExprAsWritten();
+  return Sub != nullptr && InnerMatcher.matches(*Sub, Finder, Builder);
+}
+
+AST_MATCHER(ExplicitCastExpr, addsOnlyConst) {
+  const auto *Ref = Node.getTypeAsWritten()->getAs<LValueReferenceType>();
+  if (Ref == nullptr)
+    return false;
+  const Expr *Sub = Node.getSubExprAsWritten();
+  return Sub != nullptr &&
+         Finder->getASTContext().hasSameType(Ref->getPointeeType(),
+                                             Sub->getType().withConst());
+}
+
+} // namespace
+
+UseAsConstCheck::UseAsConstCheck(StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      Inserter(Options.getLocalOrGlobal("IncludeStyle",
+                                        utils::IncludeSorter::IS_LLVM),
+               areDiagsSelfContained()),
+      IgnoreMacros(Options.getLocalOrGlobal("IgnoreMacros", true)) {}
+
+void UseAsConstCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "IncludeStyle", Inserter.getStyle());
+  Options.store(Opts, "IgnoreMacros", IgnoreMacros);
+}
+
+void UseAsConstCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      cxxStaticCastExpr(
+          unless(isTypeDependent()),
+          hasDestinationType(qualType(hasCanonicalType(
+              lValueReferenceType(pointee(qualType(isConstQualified())))))),
+          hasSourceExpressionAsWritten(
+              expr(unless(isTypeDependent()), isLValueExpr(),
+                   unless(hasType(qualType(isConstQualified()))))
----------------
zwuis wrote:

```cpp
using T = const int;
T x;
static_cast<const int&>(x)
```

IIUC this causes false positive because of missing `hasCanonicalType` matcher.

https://github.com/llvm/llvm-project/pull/210554
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