[Spikhalskiy]

A member operator call reported the provider of getArg(0)->getType(). For an operator inherited from a base class, that argument is a derived-to-base implicit cast, so the use was attributed to the base class instead of the type the operator was called on. VisitMemberExpr already strips implicit casts, so p.get() and p->x disagreed.

With libstdc++, std::shared_ptr inherits operator-> and operator* from std::__shared_ptr_access in bits/shared_ptr_base.h, so misc-include-cleaner reported <memory> as unused after p->x, while libc++, which declares them on std::shared_ptr, did not.

This strips implicit casts from the object argument the same way, and adds WalkAST tests for inherited operator+, operator-> and operator*.

Fixes #240048

[llvmorg-github-actions]

@llvm/pr-subscribers-clang-tools-extra

Author: Dmitry Spikhalsky (Spikhalskiy)

Changes

A member operator call reported the provider of getArg(0)->getType(). For an operator inherited from a base class, that argument is a derived-to-base implicit cast, so the use was attributed to the base class instead of the type the operator was called on. VisitMemberExpr already strips implicit casts, so p.get() and p->x disagreed.

With libstdc++, std::shared_ptr inherits operator-> and operator* from std::__shared_ptr_access in bits/shared_ptr_base.h, so misc-include-cleaner reported <memory> as unused after p->x, while libc++, which declares them on std::shared_ptr, did not.

This strips implicit casts from the object argument the same way, and adds WalkAST tests for inherited operator+, operator-> and operator*.

Fixes #240048

---

Full diff: https://github.com/llvm/llvm-project/pull/240052.diff

3 Files Affected:

• (modified) clang-tools-extra/docs/ReleaseNotes.md (+6)
• (modified) clang-tools-extra/include-cleaner/lib/WalkAST.cpp (+4-2)
• (modified) clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp (+15)

diff --git a/clang-tools-extra/docs/ReleaseNotes.md b/clang-tools-extra/docs/ReleaseNotes.md
index de205ae3343db9..c3481b91e6da87 100644
--- a/clang-tools-extra/docs/ReleaseNotes.md
+++ b/clang-tools-extra/docs/ReleaseNotes.md
@@ -283,6 +283,12 @@ infrastructure are described first, followed by tool-specific sections.
   {option}`IgnoreHeaders` patterns containing `/` against header paths on
   Windows.
 
+- Improved {doc}`misc-include-cleaner
+  <clang-tidy/checks/misc/include-cleaner>` check by attributing a member
+  operator inherited from a base class to the derived type, so the derived
+  type's header is no longer reported as unused. This made `<memory>` look
+  unused after `p->x` on a `std::shared_ptr` with libstdc++ but not libc++.
+
 - Fixed an infinite loop in {doc}`misc-multiple-inheritance
   <clang-tidy/checks/misc/multiple-inheritance>` when checking a class that
   inherits from itself or has a circular inheritance graph.
diff --git a/clang-tools-extra/include-cleaner/lib/WalkAST.cpp b/clang-tools-extra/include-cleaner/lib/WalkAST.cpp
index 5449411371e601..68a2cef03d86f6 100644
--- a/clang-tools-extra/include-cleaner/lib/WalkAST.cpp
+++ b/clang-tools-extra/include-cleaner/lib/WalkAST.cpp
@@ -161,8 +161,10 @@ class ASTWalker : public RecursiveASTVisitor<ASTWalker> {
       return false;
     if (auto *CD = S->getCalleeDecl()) {
       if (isa<CXXMethodDecl>(CD)) {
-        // Treat this as a regular member reference.
-        report(S->getOperatorLoc(), getMemberProvider(S->getArg(0)->getType()),
+        // Treat this as a regular member reference. Like VisitMemberExpr, look
+        // through the derived-to-base cast an inherited operator adds.
+        report(S->getOperatorLoc(),
+               getMemberProvider(S->getArg(0)->IgnoreImpCasts()->getType()),
                RefType::Implicit);
       } else {
         report(S->getOperatorLoc(), dyn_cast<NamedDecl>(CD), RefType::Implicit);
diff --git a/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp b/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp
index c9519c2e91b68a..87e78eb7750885 100644
--- a/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp
+++ b/clang-tools-extra/include-cleaner/unittests/WalkASTTest.cpp
@@ -502,6 +502,21 @@ TEST(WalkAST, Operator) {
   testWalk(
       "struct string {int operator+(string); }; using $implicit^foo = string;",
       "int k = foo() ^+ string();");
+  // Inherited member operators are attributed to the derived type, like other
+  // inherited members.
+  testWalk("struct Base { int operator+(Base); }; "
+           "struct $implicit^Derived : Base {};",
+           "int k = Derived() ^+ Derived();");
+  testWalk(R"cpp(
+      template <typename T> struct PtrBase { T *operator->(); T &operator*(); };
+      template <typename T> struct $implicit^Ptr : PtrBase<T> {};
+      struct Foo { int a; };)cpp",
+           "void test(Ptr<Foo> &V) { V^->a; }");
+  testWalk(R"cpp(
+      template <typename T> struct PtrBase { T *operator->(); T &operator*(); };
+      template <typename T> struct $implicit^Ptr : PtrBase<T> {};
+      struct Foo { int a; };)cpp",
+           "void test(Ptr<Foo> &V) { (^*V).a; }");
 }
 
 TEST(WalkAST, VarDecls) {

[github-actions]

🪟 Windows x64 Test Results

• 3452 tests passed
• 38 tests skipped

✅ The build succeeded and all tests passed.

[github-actions]

🐧 Linux x64 Test Results

• 5632 tests passed
• 8 tests skipped

✅ The build succeeded and all tests passed.