Fix NativeModule templates to work with clang (#15917)

* Fix NativeModule templates to work with clang

* Change files

Author: acoates-ms

change/react-native-windows-660aa91b-ff55-4316-a3db-b8910ba99e8c.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Fix NativeModule templates to work with clang",
+  "packageName": "react-native-windows",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}

vnext/Microsoft.ReactNative.Cxx/ModuleRegistration.h

@@ -17,19 +17,23 @@
 // The macros below are internal implementation details for macro defined in nativeModules.h
 //
 
+// ADL-based fallback: returns false for any type not tagged by the macros below.
+// Using ADL instead of explicit template specialization allows the macros to be
+// used inside a namespace (explicit specializations of a global template must
+// occur at global scope, which the macros cannot guarantee).
 template <typename T>
-struct IsReactTurboModule;
+constexpr bool ReactIsReactTurboModuleImpl(T *) noexcept {
+  return false;
+}
 
-// Default to false if no specific override
 template <typename T>
-struct IsReactTurboModule : std::false_type {};
+struct IsReactTurboModule : std::bool_constant<ReactIsReactTurboModuleImpl(static_cast<T *>(nullptr))> {};
 
 #define INTERNAL_REACT_MODULE_REGISTRATION_AND_PROVIDER(                                                            \
     moduleStruct, moduleName, eventEmitterName, isReactTurboModule)                                                 \
   struct moduleStruct;                                                                                              \
                                                                                                                     \
-  template <>                                                                                                       \
-  struct IsReactTurboModule<moduleStruct> : std::isReactTurboModule##_type {};                                      \
+  constexpr bool ReactIsReactTurboModuleImpl(moduleStruct *) noexcept { return isReactTurboModule; }                \
                                                                                                                     \
   template <class TDummy>                                                                                           \
   struct moduleStruct##_ModuleRegistration final : winrt::Microsoft::ReactNative::ModuleRegistration {              \
@@ -70,8 +74,7 @@ struct IsReactTurboModule : std::false_type {};
     moduleStruct, moduleName, eventEmitterName, isReactTurboModule)                                    \
   struct moduleStruct;                                                                                 \
                                                                                                        \
-  template <>                                                                                          \
-  struct IsReactTurboModule<moduleStruct> : std::isReactTurboModule##_type {};                         \
+  constexpr bool ReactIsReactTurboModuleImpl(moduleStruct *) noexcept { return isReactTurboModule; }   \
                                                                                                        \
   template <class TRegistry>                                                                           \
   constexpr void GetReactModuleInfo(moduleStruct *, TRegistry &registry) noexcept {                    \

vnext/Microsoft.ReactNative.Cxx/NativeModules.h

@@ -918,7 +918,7 @@ struct ModuleEventFieldInfo<TFunc<void(TArgs...)> TModule::*> {
       return [module = static_cast<ModuleType *>(module), field](IReactContext const &) noexcept {
         // Default emitter will do nothing
         // This will be replaced with a method that will call the jsi EventEmitter when JS requests the emitter
-        module->*field = [](TArgs... args) noexcept {};
+        module->*field = [](TArgs... /*args*/) noexcept {};
       };
     } else {
       return [module = static_cast<ModuleType *>(module), field, eventName, eventEmitterName](