[clang-tidy] Correctly ignore function templates in derived-method-shadowing-base-method (#185741) (#185875)

This commit fixes a false positive in the
derived-method-shadowin-base-method clang-tidy check, as described in
[ticket 185741](https://github.com/llvm/llvm-project/issues/185741)

Fixes #185741

---------

Co-authored-by: Tom James <tom.james@siemens.com>
Co-authored-by: Zeyi Xu <mitchell.xu2@gmail.com>

clang-tools-extra/clang-tidy/bugprone/DerivedMethodShadowingBaseMethodCheck.cpp

@@ -81,6 +81,10 @@ AST_MATCHER(CXXMethodDecl, nameCollidesWithMethodInBase) {
 // similar matchers are used elsewhere in LLVM
 AST_MATCHER(CXXMethodDecl, isOutOfLine) { return Node.isOutOfLine(); }
 
+AST_MATCHER(CXXMethodDecl, isTemplate) {
+  return Node.getDescribedFunctionTemplate() != nullptr;
+}
+
 } // namespace
 
 DerivedMethodShadowingBaseMethodCheck::DerivedMethodShadowingBaseMethodCheck(
@@ -94,8 +98,8 @@ void DerivedMethodShadowingBaseMethodCheck::registerMatchers(
           unless(anyOf(isOutOfLine(), isStaticStorageClass(), isImplicit(),
                        cxxConstructorDecl(), isOverride(), isPrivate(),
                        // isFinal(), //included with isOverride,
-                       // Templates are not handled yet
-                       ast_matchers::isTemplateInstantiation(),
+                       // TODO: Templates are not handled yet
+                       isTemplate(), ast_matchers::isTemplateInstantiation(),
                        ast_matchers::isExplicitTemplateSpecialization())),
           ofClass(cxxRecordDecl(isDerivedFrom(cxxRecordDecl()))
                       .bind("derived_class")),

clang-tools-extra/docs/ReleaseNotes.rst

@@ -204,6 +204,10 @@ Changes in existing checks
   <clang-tidy/checks/bugprone/casting-through-void>` check by running only on
   C++ files because suggested ``reinterpret_cast`` is not available in pure C.
 
+- Improved :doc:`bugprone-derived-method-shadowing-base-method
+  <clang-tidy/checks/bugprone/derived-method-shadowing-base-method>` check by 
+  correctly ignoring function templates.
+
 - Improved :doc:`bugprone-exception-escape
   <clang-tidy/checks/bugprone/exception-escape>` check by adding
   `TreatFunctionsWithoutSpecificationAsThrowing` option to support reporting

clang-tools-extra/test/clang-tidy/checkers/bugprone/derived-method-shadowing-base-method.cpp

@@ -137,3 +137,10 @@ public:
     void methodWithArg(MyInt *I);
     void methodWithArg(MyInt const* I);
 };
+
+class R: public Base
+{
+public:
+    template <typename T>
+    Base* getThis();
+};