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

[Baranov Victor via cfe-commits]

================
@@ -0,0 +1,140 @@
+//===----------------------------------------------------------------------===//
+//
+// 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();
+      });
+}
+
+void ShadowedNamespaceFunctionCheck::registerMatchers(MatchFinder *Finder) {
+  // Simple matcher for all function definitions
+  Finder->addMatcher(functionDecl(isDefinition()).bind("func"), this);
+}
+
+void ShadowedNamespaceFunctionCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *Func = Result.Nodes.getNodeAs<FunctionDecl>("func");
+
+  if (!Func || !Result.SourceManager)
+    return;
+
+  // Skip if not in global namespace
+  const DeclContext *DC = Func->getDeclContext();
+  if (!DC->isTranslationUnit())
+    return;
+
+  // Skip templates, static functions, main, etc.
+  if (Func->isTemplated() || Func->isStatic() || Func->isMain() ||
+      Func->isImplicit() || Func->isVariadic())
+    return;
+
+  const std::string FuncName = Func->getNameAsString();
+  if (FuncName.empty())
+    return;
+
+  const ASTContext *Context = Result.Context;
+
+  // Look for functions with the same name in namespaces
+  const FunctionDecl *ShadowedFunc = nullptr;
+  const NamespaceDecl *ShadowedNamespace = nullptr;
+
+  // Traverse all declarations in the translation unit
+  for (const auto *Decl : Context->getTranslationUnitDecl()->decls()) {
+    if (const auto *NS = dyn_cast<NamespaceDecl>(Decl)) {
+      std::tie(ShadowedFunc, ShadowedNamespace) =
+          findShadowedInNamespace(NS, Func, FuncName);
+      if (ShadowedFunc)
+        break;
+    }
+  }
----------------
vbvictor wrote:

Could you please check with `--enable-check-profiling` how fast the check work comparing to others?
If it's among the slowest, we would probably need some memoization here.

Traversing all decls on function seems like a very heavy operation.


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