Rationale (June, 2014):

This suggested extension should be investigated by EWG before any action is taken.

[Accepted at the February, 2019 meeting as part of paper P1286R2.]

The current rules requiring a defaulted member function to have an exception-specification compatible with that of the implicitly-declared function are overly constraining. It should be possible, for example, to specify that a defaulted move constructor will be non-throwing, based on knowledge available to the programmer, even if the implicitly-declared constructor would be throwing.