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2518. [fund.ts.v2] Non-member swap for propagate_const should call member swap

Section: 3.7.10 [fund.ts.v2::propagate_const.algorithms] Status: TS Submitter: Tim Song Opened: 2015-07-08 Last modified: 2017-07-30

Priority: 3

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Discussion:

Addresses: fund.ts.v2

For consistency with the rest of the standard library, the non-member swap for propagate_const should call member swap.

[2015-07, Telecon]

Both P3 and NAD were suggested.

[2016-02-20, Ville comments]

Feedback from an implementation:

The implementation of propagate_const in libstdc++ calls propagate_const's member swap from the non-member swap.

[2016-11-08, Issaquah]

Adopted during NB comment resolution

Proposed resolution:

This wording is relative to N4529.

1. Edit [propagate_const.algorithms] as indicated:

   -1- template <class T>
   constexpr void swap(propagate_const<T>& pt1, propagate_const<T>& pt2) noexcept(see below)
   

   -2- The constant-expression in the exception-specification is noexcept(swap(pt1.t_, pt2.t_)pt1.swap(pt2)).

   -3- Effects: swap(pt1.t_, pt2.t_)pt1.swap(pt2).