US062 09.04.4 [dcl.fct.def.coroutine].5 Make unhandled_exception in promise types optional P2100

[wg21bot]

Coroutine promise types are currently required to define an unhandled_exception member function. For many simple promise types, the definition of this function is simple and trivial; it just rethrows. It is unfortunate that authors of promise types are required to write this boilerplate. Many other coroutine extension points are only used if they exist, but this one is required. It would be nice if it was not required for noexcept coroutines.

Proposed change:
If the coroutine is noexcept, do not wrap the invocation of the function body in a try/catch block and do not require that promise types define an unhandled_exception method.

[jfbastien]

EWG Monday: http://wiki.edg.com/bin/view/Wg21belfast/US062

US062 Does EWG want to consider this for C++20

F	A
18	0

Motion passes. Gor, Michal and Lewis to come back with a paper.

[jfbastien]

See P2100

[jfbastien]

Based on discussion of D2100R0 Keep unhandled_exception of a promise type mandatory - a response to US062 and FR066

Reject US062 and FR066

SF	F	N	A	SA
12	8	1	0	0