[clang-tools-extra] [clang-tidy] Unsafe CRTP check (PR #82403)

[Piotr Zegar via cfe-commits]

================
@@ -0,0 +1,167 @@
+//===--- UnsafeCrtpCheck.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 "UnsafeCrtpCheck.h"
+#include "../utils/LexerUtils.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+namespace {
+// Finds a node if it's already a bound node.
+AST_MATCHER_P(CXXRecordDecl, isBoundNode, std::string, ID) {
+  return Builder->removeBindings(
+      [&](const ast_matchers::internal::BoundNodesMap &Nodes) {
+        const auto *BoundRecord = Nodes.getNodeAs<CXXRecordDecl>(ID);
+        return BoundRecord != &Node;
+      });
+}
+
+bool hasPrivateConstructor(const CXXRecordDecl *RD) {
+  for (auto &&Ctor : RD->ctors()) {
+    if (Ctor->getAccess() == AS_private)
+      return true;
+  }
+
+  return false;
+}
+
+bool isDerivedParameterBefriended(const CXXRecordDecl *CRTP,
+                                  const NamedDecl *Param) {
+  for (auto &&Friend : CRTP->friends()) {
+    const auto *TTPT =
+        dyn_cast<TemplateTypeParmType>(Friend->getFriendType()->getType());
+
+    if (TTPT && TTPT->getDecl() == Param)
+      return true;
+  }
+
+  return false;
+}
+
+bool isDerivedClassBefriended(const CXXRecordDecl *CRTP,
+                              const CXXRecordDecl *Derived) {
+  for (auto &&Friend : CRTP->friends()) {
+    if (Friend->getFriendType()->getType()->getAsCXXRecordDecl() == Derived)
+      return true;
+  }
+
+  return false;
+}
+
+std::optional<const NamedDecl *>
+getDerivedParameter(const ClassTemplateSpecializationDecl *CRTP,
----------------
PiotrZSL wrote:

You still should be able to read 'T' from templateArgument() via [getAsTemplate](https://clang.llvm.org/doxygen/classclang_1_1TemplateArgument.html#a83db07b04d0629a21962a65e8a8bfcc3) ()

https://github.com/llvm/llvm-project/pull/82403