1+++ 2title = "`is_error_type<E>`" 3description = "A customisable integral constant type true for `E` types which are to receive error throwing no-value policies." 4+++ 5 6A customisable integral constant type true for `E` types which are to receive 7error throwing no-value policies. Special weakened implicit construction enable 8is available for integral `T` types when combined with `E` types in this 9whitelist -- this permits `boost_result<int, boost::system::errc::errc_t` to 10retain its implicit constructors, despite the fact that `errc_t` as a C enum 11has an implicit conversion to `int`. 12 13*Overridable*: By template specialisation into the `trait` namespace. 14 15*Default*: False. Specialisations to true exist for: 16 17- `<boost/outcome/boost_result.hpp>` 18 - `boost::system::error_code` 19 - `boost::system::errc::errc_t` 20 - `boost::exception_ptr` 21 22- `<boost/outcome/std_result.hpp>` 23 - `std::error_code` 24 - `std::errc` 25 - `std::exception_ptr` 26 27*Namespace*: `BOOST_OUTCOME_V2_NAMESPACE::trait` 28 29*Header*: `<boost/outcome/trait.hpp>`