[clang-tools-extra] [clang-tidy] New bugprone-method-hiding check (PR #154746)

[via cfe-commits]

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@@ -0,0 +1,129 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "MethodHidingCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include <stack>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+namespace {
+
+bool sameBasicType(const ParmVarDecl *Lhs, const ParmVarDecl *Rhs) {
+  if (Lhs && Rhs) {
+    return Lhs->getType()
+               .getCanonicalType()
+               .getNonReferenceType()
+               .getUnqualifiedType() == Rhs->getType()
+                                            .getCanonicalType()
+                                            .getNonReferenceType()
+                                            .getUnqualifiedType();
+  }
+  return false;
+}
+
+bool namesCollide(const CXXMethodDecl &Lhs, const CXXMethodDecl &Rhs) {
+  if (Lhs.getNameAsString() != Rhs.getNameAsString())
+    return false;
+  if (Lhs.isConst() != Rhs.isConst())
+    return false;
+  if (Lhs.getNumParams() != Rhs.getNumParams())
+    return false;
+  for (unsigned int It = 0; It < Lhs.getNumParams(); ++It)
+    if (!sameBasicType(Lhs.getParamDecl(It), Rhs.getParamDecl(It)))
+      return false;
+  // Templates are not handled yet
+  if (Lhs.isTemplated() || Rhs.isTemplated())
+    return false;
+  if (Lhs.isTemplateInstantiation() || Rhs.isTemplateInstantiation())
+    return false;
+  if (Lhs.isFunctionTemplateSpecialization() ||
+      Rhs.isFunctionTemplateSpecialization())
+    return false;
+  return true;
+}
+
+AST_MATCHER(CXXMethodDecl, nameCollidesWithMethodInBase) {
+  const CXXRecordDecl *DerivedClass = Node.getParent();
+  for (const auto &Base : DerivedClass->bases()) {
+    std::stack<const CXXBaseSpecifier *> Stack;
+    Stack.push(&Base);
+    while (!Stack.empty()) {
+      const CXXBaseSpecifier *CurrentBaseSpec = Stack.top();
+      Stack.pop();
+
+      if (CurrentBaseSpec->getAccessSpecifier() ==
+          clang::AccessSpecifier::AS_private)
+        continue;
+
+      const auto *CurrentRecord =
+          CurrentBaseSpec->getType()->getAsCXXRecordDecl();
+      if (!CurrentRecord)
+        continue;
+
+      for (const auto &BaseMethod : CurrentRecord->methods()) {
+        if (namesCollide(*BaseMethod, Node)) {
+          ast_matchers::internal::BoundNodesTreeBuilder Result(*Builder);
+          Builder->setBinding("base_method",
+                              clang::DynTypedNode::create(*BaseMethod));
+          return true;
+        }
+      }
+
+      for (const auto &SubBase : CurrentRecord->bases())
+        Stack.push(&SubBase);
+    }
+  }
+  return false;
+}
+
+// Same as clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp,
+// similar matchers are used elsewhere in LLVM
+AST_MATCHER(CXXMethodDecl, isOutOfLine) { return Node.isOutOfLine(); }
+
+} // namespace
+
+MethodHidingCheck::MethodHidingCheck(StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context) {}
+
+void MethodHidingCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      cxxMethodDecl(
+          unless(anyOf(isOutOfLine(), isStaticStorageClass(), isImplicit(),
+                       cxxConstructorDecl(), isOverride(),
+                       // isFinal(), //included with isOverride,
+                       isPrivate())),
----------------
t-a-james wrote:

If `Derived::foo()` is private then calling it downstream is a compiler error, which makes it much harder to accidentally call the wrong method

https://github.com/llvm/llvm-project/pull/154746