[clang-tidy] Rename out-of-line function definitions

Member function templates defined out-of-line were resulting in
conflicting naming failures with overlapping usage sets. With this
change, out-of-line definitions are treated as a usage of the failure
which is the inline declaration.

Author: revane

clang-tools-extra/clang-tidy/utils/RenamerClangTidyCheck.cpp

@@ -123,6 +123,9 @@ static const NamedDecl *getFailureForNamedDecl(const NamedDecl *ND) {
   if (const auto *Method = dyn_cast<CXXMethodDecl>(ND)) {
     if (const CXXMethodDecl *Overridden = getOverrideMethod(Method))
       Canonical = cast<NamedDecl>(Overridden->getCanonicalDecl());
+    else if (const FunctionTemplateDecl *Primary = Method->getPrimaryTemplate())
+      Canonical =
+          cast<NamedDecl>(Primary->getTemplatedDecl()->getCanonicalDecl());
 
     if (Canonical != ND)
       return Canonical;

clang-tools-extra/docs/ReleaseNotes.rst

@@ -343,7 +343,8 @@ Changes in existing checks
   <clang-tidy/checks/readability/identifier-naming>` check in `GetConfigPerFile`
   mode by resolving symbolic links to header files. Fixed handling of Hungarian
   Prefix when configured to `LowerCase`. Added support for renaming designated
-  initializers. Added support for renaming macro arguments.
+  initializers. Added support for renaming macro arguments. Fixed renaming
+  conflicts arising from out-of-line member function template definitions.
 
 - Improved :doc:`readability-implicit-bool-conversion
   <clang-tidy/checks/readability/implicit-bool-conversion>` check to provide

clang-tools-extra/test/clang-tidy/checkers/readability/identifier-naming-ool.cpp

@@ -0,0 +1,30 @@
+// RUN: %check_clang_tidy %s readability-identifier-naming %t -std=c++20 \
+// RUN:   --config='{CheckOptions: { \
+// RUN:     readability-identifier-naming.MethodCase: CamelCase, \
+// RUN:  }}'
+
+namespace SomeNamespace {
+namespace Inner {
+
+class SomeClass {
+public:
+    template <typename T>
+    int someMethod();
+// CHECK-MESSAGES: :[[@LINE-1]]:9: warning: invalid case style for method 'someMethod' [readability-identifier-naming]
+// CHECK-FIXES: {{^}}    int SomeMethod();
+};
+template <typename T>
+int SomeClass::someMethod() {
+// CHECK-FIXES: {{^}}int SomeClass::SomeMethod() {
+    return 5;
+}
+
+} // namespace Inner
+
+void someFunc() {
+    Inner::SomeClass S;
+    S.someMethod<int>();
+// CHECK-FIXES: {{^}}    S.SomeMethod<int>();
+}
+
+} // namespace SomeNamespace