[clang] [clang-tools-extra] [clang-tidy] fix misc-unconventional-assign-operator entity match (PR #154430)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov created https://github.com/llvm/llvm-project/pull/154430

Makes sure UnconventionalAssignOperatorCheck checks if the types reference the same entity, not the exact declaration.

This adds a new matcher to support this check.

This fixes a regression introduced by #147835. Since this regression was never released, there are no release notes.

Fixes #153770

>From 08806abfbfbc9073964b9889007689c39aef8263 Mon Sep 17 00:00:00 2001
From: Matheus Izvekov <mizvekov at gmail.com>
Date: Tue, 19 Aug 2025 18:49:24 -0300
Subject: [PATCH] [clang-tidy] fix misc-unconventional-assign-operator entity
 match

Makes sure UnconventionalAssignOperatorCheck checks if the types reference the
same entity, not the exact declaration.

This adds a new matcher to support this check.

This fixes a regression introduced by #147835. Since this regression was never
released, there are no release notes.

Fixes #153770
---
 .../clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp | 8 +++++---
 .../checkers/misc/unconventional-assign-operator.cpp      | 8 ++++++++
 clang/include/clang/ASTMatchers/ASTMatchers.h             | 8 ++++++++
 clang/lib/ASTMatchers/Dynamic/Registry.cpp                | 1 +
 4 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp b/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp
index 3fdaf9239f6af..8200239b982a0 100644
--- a/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp
@@ -29,11 +29,13 @@ void UnconventionalAssignOperatorCheck::registerMatchers(
   const auto HasGoodReturnType =
       cxxMethodDecl(returns(hasCanonicalType(lValueReferenceType(pointee(
           unless(isConstQualified()),
-          anyOf(autoType(), hasDeclaration(equalsBoundNode("class"))))))));
+          anyOf(autoType(),
+                hasDeclaration(declaresSameEntityAsBoundNode("class"))))))));
 
   const auto IsSelf = qualType(hasCanonicalType(
-      anyOf(hasDeclaration(equalsBoundNode("class")),
-            referenceType(pointee(hasDeclaration(equalsBoundNode("class")))))));
+      anyOf(hasDeclaration(declaresSameEntityAsBoundNode("class")),
+            referenceType(pointee(
+                hasDeclaration(declaresSameEntityAsBoundNode("class")))))));
   const auto IsAssign =
       cxxMethodDecl(unless(anyOf(isDeleted(), isPrivate(), isImplicit())),
                     hasName("operator="), ofClass(recordDecl().bind("class")))
diff --git a/clang-tools-extra/test/clang-tidy/checkers/misc/unconventional-assign-operator.cpp b/clang-tools-extra/test/clang-tidy/checkers/misc/unconventional-assign-operator.cpp
index 28b53ae4af63d..d7a5797cc2844 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/misc/unconventional-assign-operator.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/misc/unconventional-assign-operator.cpp
@@ -176,3 +176,11 @@ struct TemplateAssignment {
   }
 };
 }
+
+namespace GH153770 {
+  struct A;
+  struct A {
+    A() = default;
+    A& operator=(const A&) = default;
+  };
+} // namespace GH153770
diff --git a/clang/include/clang/ASTMatchers/ASTMatchers.h b/clang/include/clang/ASTMatchers/ASTMatchers.h
index cbd931cabd806..289711ddfb1b8 100644
--- a/clang/include/clang/ASTMatchers/ASTMatchers.h
+++ b/clang/include/clang/ASTMatchers/ASTMatchers.h
@@ -5739,6 +5739,14 @@ AST_POLYMORPHIC_MATCHER_P(equalsBoundNode,
   return Builder->removeBindings(Predicate);
 }
 
+/// Matches a declaration if it declares the same entity as the node previously
+/// bound to \p ID.
+AST_MATCHER_P(Decl, declaresSameEntityAsBoundNode, std::string, ID) {
+  return Builder->removeBindings([&](const internal::BoundNodesMap &Nodes) {
+    return !clang::declaresSameEntity(&Node, Nodes.getNodeAs<Decl>(ID));
+  });
+}
+
 /// Matches the condition variable statement in an if statement.
 ///
 /// Given
diff --git a/clang/lib/ASTMatchers/Dynamic/Registry.cpp b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
index 7f6a6aaed1734..48a7b91969aef 100644
--- a/clang/lib/ASTMatchers/Dynamic/Registry.cpp
+++ b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
@@ -240,6 +240,7 @@ RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(enumDecl);
   REGISTER_MATCHER(enumType);
   REGISTER_MATCHER(equalsBoundNode);
+  REGISTER_MATCHER(declaresSameEntityAsBoundNode);
   REGISTER_MATCHER(equalsIntegralValue);
   REGISTER_MATCHER(explicitCastExpr);
   REGISTER_MATCHER(exportDecl);