[clang-tools-extra] [clang-tidy] Fix false positives with deducing this in `readability-convert-member-functions-to-static` check (PR #141391)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

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

Author: None (flovent)

<details>
<summary>Changes</summary>

Fixes #<!-- -->141381.

Add check for `DeclRefExpr` which points to an explicit object parameter.

---
Full diff: https://github.com/llvm/llvm-project/pull/141391.diff


3 Files Affected:

- (modified) clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.cpp (+10) 
- (modified) clang-tools-extra/docs/ReleaseNotes.rst (+4) 
- (added) clang-tools-extra/test/clang-tidy/checkers/readability/convert-member-functions-to-static-deducing-this.cpp (+14) 


``````````diff
diff --git a/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.cpp b/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.cpp
index 1284df6bd99cf..5cdd00414e01e 100644
--- a/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.cpp
@@ -62,6 +62,16 @@ AST_MATCHER(CXXMethodDecl, usesThis) {
       return false; // Stop traversal.
     }
 
+    bool VisitDeclRefExpr(const DeclRefExpr *E) {
+      if (const auto *PVD = dyn_cast_if_present<ParmVarDecl>(E->getDecl());
+          PVD && PVD->isExplicitObjectParameter()) {
+        Used = true;
+        return false; // Stop traversal.
+      }
+
+      return true;
+    }
+
     // If we enter a class declaration, don't traverse into it as any usages of
     // `this` will correspond to the nested class.
     bool TraverseCXXRecordDecl(CXXRecordDecl *RD) { return true; }
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 8611b5e0af272..a138272cc8e39 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -234,6 +234,10 @@ Changes in existing checks
   tolerating fix-it breaking compilation when functions is used as pointers
   to avoid matching usage of functions within the current compilation unit.
 
+- Improved :doc:`readability-convert-member-functions-to-static
+  <clang-tidy/checks/readability/convert-member-functions-to-static>` check by
+  fixing false positives on member functions with an explicit object parameter.
+
 Removed checks
 ^^^^^^^^^^^^^^
 
diff --git a/clang-tools-extra/test/clang-tidy/checkers/readability/convert-member-functions-to-static-deducing-this.cpp b/clang-tools-extra/test/clang-tidy/checkers/readability/convert-member-functions-to-static-deducing-this.cpp
new file mode 100644
index 0000000000000..bb9755abc9cfa
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability/convert-member-functions-to-static-deducing-this.cpp
@@ -0,0 +1,14 @@
+// RUN: %check_clang_tidy -std=c++23 %s readability-convert-member-functions-to-static %t
+
+namespace std{
+  class string {};
+  void println(const char *format, const std::string &str) {}
+}
+
+namespace PR141381 {
+struct Hello {
+  std::string str_;
+
+  void hello(this Hello &self) { std::println("Hello, {0}!", self.str_); }
+};
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/141391