Adding holder_caster typename SFINAE = void hooks to help work around the current lack of smart-pointer interoperability (#2833)

* Adding move_only_holder_caster `typename SFINAE = void` to enable external specializations.

* Adding SFINAE hook also to copyable_holder_caster, for uniformity, with comment to explain the purpose.
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Ralf W. Grosse-Kunstleve 2021-01-30 15:02:24 -05:00 committed by GitHub
parent 23c3edcf21
commit 932769b038
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@ -1525,7 +1525,11 @@ struct holder_helper {
};
/// Type caster for holder types like std::shared_ptr, etc.
template <typename type, typename holder_type>
/// The SFINAE hook is provided to help work around the current lack of support
/// for smart-pointer interoperability. Please consider it an implementation
/// detail that may change in the future, as formal support for smart-pointer
/// interoperability is added into pybind11.
template <typename type, typename holder_type, typename SFINAE = void>
struct copyable_holder_caster : public type_caster_base<type> {
public:
using base = type_caster_base<type>;
@ -1600,7 +1604,10 @@ protected:
template <typename T>
class type_caster<std::shared_ptr<T>> : public copyable_holder_caster<T, std::shared_ptr<T>> { };
template <typename type, typename holder_type>
/// Type caster for holder types like std::unique_ptr.
/// Please consider the SFINAE hook an implementation detail, as explained
/// in the comment for the copyable_holder_caster.
template <typename type, typename holder_type, typename SFINAE = void>
struct move_only_holder_caster {
static_assert(std::is_base_of<type_caster_base<type>, type_caster<type>>::value,
"Holder classes are only supported for custom types");