A customisable integral constant type true for E types which are to receive error throwing no-value policies. Special weakened implicit construction enable is available for integral T types when combined with E types in this whitelist – this permits boost_result<int, boost::system::errc::errc_t to retain its implicit constructors, despite the fact that errc_t as a C enum has an implicit conversion to int.

Overridable: By template specialisation into the trait namespace.

Default: False. Specialisations to true exist for:

Namespace: OUTCOME_V2_NAMESPACE::trait

Header: <outcome/trait.hpp>