[clang-tools-extra] [clang-tidy] Fix erroneous warning to make deleted function public (PR #182577)

[Jakob Widauer via cfe-commits]

https://github.com/jwidauer updated https://github.com/llvm/llvm-project/pull/182577

>From 67237569a2503d63573378ddc71c1f25d29d231f Mon Sep 17 00:00:00 2001
From: Jakob Widauer <jakob.widauer at gmail.com>
Date: Fri, 20 Feb 2026 20:17:30 +0100
Subject: [PATCH] [clang-tidy] Fix erroneous warning to make deleted function
 public

---
 .../modernize/UseEqualsDeleteCheck.cpp        | 22 ++++-
 clang-tools-extra/docs/ReleaseNotes.rst       |  5 ++
 .../checkers/modernize/use-equals-delete.cpp  | 84 +++++++++++++------
 3 files changed, 86 insertions(+), 25 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.cpp
index 25140152219cf..cc1d858a2809c 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseEqualsDeleteCheck.cpp
@@ -39,6 +39,22 @@ AST_MATCHER(CXXMethodDecl, isSpecialFunction) {
   return isa<CXXDestructorDecl>(Node) || Node.isCopyAssignmentOperator() ||
          Node.isMoveAssignmentOperator();
 }
+
+AST_MATCHER(CXXMethodDecl, hasPublicOverload) {
+  const DeclContext::lookup_result LookupResult =
+      Node.getParent()->lookup(Node.getNameInfo().getName());
+
+  if (LookupResult.isSingleResult())
+    return false; // No overloads
+
+  static constexpr auto IsPublicOverload = [](const Decl *Overload) {
+    return (isa<CXXMethodDecl>(Overload) ||
+            isa<FunctionTemplateDecl>(Overload)) &&
+           Overload->getAccess() == AS_public;
+  };
+
+  return llvm::any_of(LookupResult, IsPublicOverload);
+}
 } // namespace
 
 static constexpr char SpecialFunction[] = "SpecialFunction";
@@ -66,8 +82,12 @@ void UseEqualsDeleteCheck::registerMatchers(MatchFinder *Finder) {
           .bind(SpecialFunction),
       this);
 
+  // Add a matcher for deleted private member functions, with a public overload,
+  // to recommend moving them to the public section.
   Finder->addMatcher(
-      cxxMethodDecl(isDeleted(), unless(isPublic())).bind(DeletedNotPublic),
+      cxxMethodDecl(isDeleted(), unless(isPublic()),
+                    anyOf(hasPublicOverload(), isSpecialFunction()))
+          .bind(DeletedNotPublic),
       this);
 }
 
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 22992c5a1d5d8..7caff15e13947 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -151,6 +151,11 @@ New check aliases
 Changes in existing checks
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+- Improved :doc:`modernize-use-equals-delete
+  <clang-tidy/checks/modernize/use-equals-delete>` check by only warning on 
+  private deleted functions, if they do not have a public overload or are a
+  special member function.
+
 - Improved :doc:`bugprone-argument-comment
   <clang-tidy/checks/bugprone/argument-comment>` to also check for C++11
   inherited constructors.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-equals-delete.cpp b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-equals-delete.cpp
index 061a2722b1ac7..aa63cbcd356a5 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-equals-delete.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-equals-delete.cpp
@@ -194,28 +194,64 @@ class C {
 
 namespace PR33759 {
 
-  class Number {
-    private:
-      Number();
-      ~Number();
-
-    public:
-      static Number& getNumber() {
-        static Number number;
-        return number;
-      }
-
-      int getIntValue() { return (int)someFloat; }
-      float getFloatValue() { return someFloat; }
-    private:
-      float someFloat;
-  };
-
-  class Number2 {
-    private:
-      Number2();
-      ~Number2();
-    public:
-      static Number& getNumber();
-  };
+class Number {
+  private:
+    Number();
+    ~Number();
+
+  public:
+    static Number& getNumber() {
+      static Number number;
+      return number;
+    }
+
+    int getIntValue() { return (int)someFloat; }
+    float getFloatValue() { return someFloat; }
+  private:
+    float someFloat;
+};
+
+class Number2 {
+  private:
+    Number2();
+    ~Number2();
+  public:
+    static Number& getNumber();
+};
+}
+
+namespace PR54276 {
+
+class PrivateDeletedFunctionWithPublicOverload {
+  public:
+    void foo() {}
+  private:
+    void foo(int) = delete;
+    // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: deleted member function should be public [modernize-use-equals-delete]
+};
+
+class PrivateDeletedFunctionWithPrivateOverload {
+  private:
+    void foo() {}
+    void foo(int) = delete;
+};
+
+class PrivateDeletedFunctionTemplateWithPublicOverload {
+  public:
+    template<typename T>
+    void foo(T) {}
+  private:
+    template<typename T>
+    void foo(T, int) = delete;
+    // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: deleted member function should be public [modernize-use-equals-delete]
+};
+
+class PrivateDeletedFunctionTemplateWithPrivateOverload {
+  private:
+    template<typename T>
+    void foo(T) {}
+    template<typename T>
+    void foo(T, int) = delete;
+};
+
 }