[clang-tools-extra] [clang-tidy] Add misc-shadowed-namespace-function check (PR #168406)

[Yanzuo Liu via cfe-commits]

================
@@ -0,0 +1,124 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "ShadowedNamespaceFunctionCheck.h"
+#include "../utils/FixItHintUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "llvm/ADT/STLExtras.h"
+
+using namespace clang;
+using namespace clang::ast_matchers;
+using namespace clang::tidy;
+
+namespace clang::tidy::misc {
+
+static bool hasSameParameters(const FunctionDecl *Func1,
+                              const FunctionDecl *Func2) {
+  if (Func1->param_size() != Func2->param_size())
+    return false;
+
+  return llvm::all_of_zip(
+      Func1->parameters(), Func2->parameters(),
+      [](const ParmVarDecl *Param1, const ParmVarDecl *Param2) {
+        return Param1->getType().getCanonicalType() ==
+               Param2->getType().getCanonicalType();
+      });
+}
+
+static std::pair<const FunctionDecl *, const NamespaceDecl *>
+findShadowedInNamespace(const NamespaceDecl *NS, const FunctionDecl *GlobalFunc,
+                        const std::string &GlobalFuncName) {
+
+  if (NS->isAnonymousNamespace())
+    return {nullptr, nullptr};
+
+  for (const auto *Decl : NS->decls()) {
+    // Check nested namespaces
+    if (const auto *NestedNS = dyn_cast<NamespaceDecl>(Decl)) {
+      auto [ShadowedFunc, ShadowedNamespace] =
+          findShadowedInNamespace(NestedNS, GlobalFunc, GlobalFuncName);
+      if (ShadowedFunc)
+        return {ShadowedFunc, ShadowedNamespace};
+    }
+
+    // Check functions
+    if (const auto *Func = dyn_cast<FunctionDecl>(Decl)) {
+      if (Func == GlobalFunc || Func->isTemplated() ||
+          Func->isThisDeclarationADefinition())
+        continue;
+
+      if (Func->getNameAsString() == GlobalFuncName && !Func->isVariadic() &&
+          hasSameParameters(Func, GlobalFunc) &&
+          Func->getReturnType().getCanonicalType() ==
+              GlobalFunc->getReturnType().getCanonicalType()) {
+        return {Func, NS};
+      }
+    }
+  }
+  return {nullptr, nullptr};
+}
+
+void ShadowedNamespaceFunctionCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      functionDecl(isDefinition(), decl(hasDeclContext(translationUnitDecl())),
+                   unless(anyOf(isImplicit(), isVariadic(), isMain(),
+                                isStaticStorageClass(),
+                                ast_matchers::isTemplateInstantiation())))
+          .bind("func"),
+      this);
+}
+
+void ShadowedNamespaceFunctionCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *Func = Result.Nodes.getNodeAs<FunctionDecl>("func");
+
+  const std::string FuncName = Func->getNameAsString();
----------------
zwuis wrote:

Can we use `NamedDecl::getName()` to reduce copy?

https://github.com/llvm/llvm-project/pull/168406