[core] Fix compile-time loop() detection for multiple inheritance (#14411)

esphome/core/application.h

@@ -118,6 +118,14 @@ void original_setup();  // NOLINT(readability-redundant-declaration) - used by c
 
 namespace esphome {
 
+/// SFINAE helper: detects whether T overrides Component::loop().
+/// When &T::loop is ambiguous (multiple inheritance with separate loop() methods),
+/// the ambiguity itself proves an override exists, so the true_type default is correct.
+template<typename T, typename = void> struct HasLoopOverride : std::true_type {};
+template<typename T>
+struct HasLoopOverride<T, std::void_t<decltype(&T::loop)>>
+    : std::bool_constant<!std::is_same_v<decltype(&T::loop), decltype(&Component::loop)>> {};
+
 // Teardown timeout constant (in milliseconds)
 // For reboots, it's more important to shut down quickly than disconnect cleanly
 // since we're not entering deep sleep. The only consequence of not shutting down
@@ -544,10 +552,9 @@ class Application {
 #endif
 
   /// Register a component, detecting loop() override at compile time.
-  /// The template resolves &T::loop vs &Component::loop as a constexpr bool
-  /// and forwards it to register_component_impl_ which stores it in component_state_.
+  /// Uses HasLoopOverride<T> which handles ambiguous &T::loop from multiple inheritance.
   template<typename T> void register_component_(T *comp) {
-    this->register_component_impl_(comp, !std::is_same_v<decltype(&T::loop), decltype(&Component::loop)>);
+    this->register_component_impl_(comp, HasLoopOverride<T>::value);
   }
 
   void register_component_impl_(Component *comp, bool has_loop);

esphome/core/config.py

@@ -517,9 +517,10 @@ async def _add_looping_components() -> None:
         return
 
     # Build constexpr sum for the exact count, deduplicating by type
+    # Uses HasLoopOverride<T> which handles ambiguous &T::loop from multiple inheritance
     type_counts = Counter(entries)
     terms = [
-        f"({count} * !std::is_same_v<decltype(&{cpp_type}::loop), decltype(&Component::loop)>)"
+        f"({count} * HasLoopOverride<{cpp_type}>::value)"
         for cpp_type, count in type_counts.items()
     ]
     constexpr_expr = " + \\\n  ".join(terms)