auto failure(T &&, …) - Boost.Outcome documentation

# `auto failure(T &&, ...)`

Returns appropriate type sugar for constructing an unsuccessful result or outcome, usually `failure_type<EC, EP = void>` with a decayed `T`.

Two default overloads are provided, one taking a single required parameter with optional spare storage value parameter returning `failure_type<std::decay_t<T>>`, the other taking two required parameters with optional spare storage value parameter returning `failure_type<std::decay_t<T>, std::decay_t<U>>`. Both overloads perfectly forward their inputs.

Note that `failure()` overloads are permitted by Outcome to return something other than `failure_type`. For example, `basic_result`’s `auto as_failure() const &` returns whatever type `failure()` returns, and `BOOST_OUTCOME_TRY(var, expr)` by default returns for failure whatever `.as_failure()` returns. This can be useful to have `BOOST_OUTCOME_TRY(...}` propagate on failure something custom for some specific input `basic_result` or `basic_outcome`.

Overridable: By Argument Dependent Lookup (ADL).

Requires: Always available.

Namespace: `BOOST_OUTCOME_V2_NAMESPACE`

Header: `<boost/outcome/success_failure.hpp>`

Last revised: February 23, 2021 at 17:37:27 UTC