Make the const-removal clearly visible. This simplifies the production code changes significantly.

For background see: https://claude.ai/share/4085d9ab-a859-44cc-bb56-450e472f817a

Author: rwgk

include/pybind11/detail/init.h

@@ -167,7 +167,12 @@ void construct(value_and_holder &v_h, Holder<Class> holder, bool need_alias) {
                          "is not an alias instance");
     }
 
-    v_h.value_ptr<typename std::remove_pointer<decltype(ptr)>::type>() = ptr;
+    // Cast away constness to store in void* storage.
+    // The value_and_holder storage is fundamentally untyped (void**), so we lose
+    // const-correctness here by design. The const qualifier will be restored
+    // when the pointer is later retrieved and cast back to the original type.
+    // This explicit const_cast makes the const-removal clearly visible.
+    v_h.value_ptr() = const_cast<void *>(static_cast<const void *>(ptr));
     v_h.type->init_instance(v_h.inst, &holder);
 }
 

include/pybind11/detail/value_and_holder.h

@@ -33,7 +33,7 @@ struct value_and_holder {
 
     template <typename V = void>
     V *&value_ptr() const {
-        return cast_void<V>(vh[0]);
+        return reinterpret_cast<V *&>(vh[0]);
     }
     // True if this `value_and_holder` has a non-null value pointer
     explicit operator bool() const { return value_ptr() != nullptr; }
@@ -72,17 +72,6 @@ struct value_and_holder {
             inst->nonsimple.status[index] &= (std::uint8_t) ~instance::status_instance_registered;
         }
     }
-
-private:
-    template <typename V, detail::enable_if_t<!std::is_const<V>::value, bool> = true>
-    static V *&cast_void(void *&ptr) {
-        return reinterpret_cast<V *&>(ptr);
-    }
-
-    template <typename V, detail::enable_if_t<std::is_const<V>::value, bool> = true>
-    static V *&cast_void(void *&ptr) {
-        return reinterpret_cast<V *&>(const_cast<const void *&>(ptr));
-    }
 };
 
 // This is a semi-public API to check if the corresponding instance has been constructed with a