Evaluate within a coroutine an expression which results in a type matching the following customisation points, assigning T to a variable called var if successful, immediately returning try_operation_return_as(X) from the calling function if unsuccessful:

• BOOST_OUTCOME_V2_NAMESPACE::try_operation_has_value(X)
• BOOST_OUTCOME_V2_NAMESPACE::try_operation_return_as(X)
• BOOST_OUTCOME_V2_NAMESPACE::try_operation_extract_value(X)

Default overloads for these customisation points are provided. See the recipe for supporting foreign input to BOOST_OUTCOME_TRY.

Hints are given to the compiler that the expression will be unsuccessful. If you expect success, you should use BOOST_OUTCOME_CO_TRY(var, expr) instead.

Overridable: Not overridable.

Definition: See BOOST_OUTCOME_CO_TRYV(expr) for most of the mechanics.

If successful, an auto &&var is initialised to the expression result’s .assume_value() if available, else to its .value(). This binds a reference possibly to the T stored inside the bound result of the expression, but possibly also to a temporary emitted from the value observer function.

Header: <boost/outcome/try.hpp>