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

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

Fixes #141381.

---------

Co-authored-by: fubowen <[email protected]>
Co-authored-by: flovent <[email protected]>

Author: 3 people

clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStatic.cpp

@@ -81,7 +81,8 @@ void ConvertMemberFunctionsToStatic::registerMatchers(MatchFinder *Finder) {
           unless(anyOf(
               isExpansionInSystemHeader(), isVirtual(), isStatic(),
               hasTrivialBody(), isOverloadedOperator(), cxxConstructorDecl(),
-              cxxDestructorDecl(), cxxConversionDecl(), isTemplate(),
+              cxxDestructorDecl(), cxxConversionDecl(),
+              isExplicitObjectMemberFunction(), isTemplate(),
               isDependentContext(),
               ofClass(anyOf(
                   isLambda(),

clang-tools-extra/docs/ReleaseNotes.rst

@@ -256,6 +256,10 @@ 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.
+
 - Improved :doc:`readability-math-missing-parentheses
   <clang-tidy/checks/readability/math-missing-parentheses>` check by fixing
   false negatives where math expressions are the operand of assignment operators

clang-tools-extra/test/clang-tidy/checkers/readability/convert-member-functions-to-static-deducing-this.cpp

@@ -0,0 +1,22 @@
+// RUN: %check_clang_tidy -std=c++23-or-later %s readability-convert-member-functions-to-static %t
+
+namespace std{
+  class string {};
+  void println(const char *format, const std::string &str) {}
+}
+
+struct Hello {
+  std::string str_;
+
+  void ByValueSelf(this Hello self) { std::println("Hello, {0}!", self.str_); }
+
+  void ByLRefSelf(this Hello &self) { std::println("Hello, {0}!", self.str_); }
+
+  void ByRRefSelf(this Hello&& self) {}
+
+  template<typename Self> void ByForwardRefSelf(this Self&& self) {}
+
+  void MultiParam(this Hello &self, int a, double b) {}
+
+  void UnnamedExplicitObjectParam(this Hello &) {}
+};