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Section: 126.96.36.199 [expos.only.func] Status: Tentatively Resolved Submitter: Marshall Clow Opened: 2017-07-11 Last modified: 2019-06-22
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In several places in this Clause the operation DECAY_COPY(x) is used. All such uses mean call the function decay_copy(x) and use the result, where decay_copy is defined as follows:
but decay_copy is not defined in any synopsis.The Ranges TS has a similar use of DECAY_COPY, except that theirs is also constexpr and noexcept. We should mark the function decay_copy as "exposition only" and constexpr and noexcept.
[2017-07-16, Daniel comments]
Currently there exists no proper way to mark decay_copy as conditionally noexcept as explained in N3255 section "Adding to the Standard". This is also slighly related to the request to add an is_nothrow_convertible trait, as requested by LWG 2040.
[ 2017-11-01 P3 as result of c++std-lib online vote. ]
[2019-03-22; Daniel comments]
Starting with N4800 have now a constexpr and conditionally noexcept decay-copy in the working draft (188.8.131.52 [expos.only.func]). The pre-condition for that specification helper became possible by adoption of P0758R1, which introduced the missing is_nothrow_convertible trait.
Rationale:Resolved by editorial creation of decay-copy after acceptance of P0758R1.