[Boost-bugs] [Boost C++ Libraries] #12652: boost::optional<DefaultConstructable>::operator= chooses wrong overload for {}

Subject: [Boost-bugs] [Boost C++ Libraries] #12652: boost::optional<DefaultConstructable>::operator= chooses wrong overload for {}
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-12-07 01:03:10

#12652: boost::optional<DefaultConstructable>::operator= chooses wrong overload for
{}
------------------------------+-----------------------
 Reporter:  mathias@…         |      Owner:  fcacciola
     Type:  Bugs              |     Status:  new
Milestone:  To Be Determined  |  Component:  optional
  Version:  Boost 1.61.0      |   Severity:  Problem
 Keywords:                    |
------------------------------+-----------------------
 {{{
 boost::optional<int> op = 5; // creates engaged optional
 op = {}; // currently does op = 0;
 }}}

 For most types operator={} assigns from a value-constructed value of that
 type. That is the behavior of std::experimental::optional but not
 boost::optional<T>. It chooses the T&& overload. I think the standard
 avoids it by having the assign-from-T operator= be templated on U instead,
 which doesn't match {}.

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Ticket URL: <https://svn.boost.org/trac/boost/ticket/12652>
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