Re: [Boost-bugs] [Boost C++ Libraries] #12788: optional 1.63 no longer can be initialized from '<brace-enclosed initializer list>'

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #12788: optional 1.63 no longer can be initialized from '<brace-enclosed initializer list>'
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2017-02-24 13:37:41

#12788: optional 1.63 no longer can be initialized from '<brace-enclosed
initializer list>'
-------------------------------+----------------------
  Reporter:  piotrwn1@…        |      Owner:  akrzemi1
      Type:  Bugs              |     Status:  closed
 Milestone:  To Be Determined  |  Component:  optional
   Version:  Boost 1.63.0      |   Severity:  Problem
Resolution:  invalid           |   Keywords:
-------------------------------+----------------------
Changes (by akrzemi1):

 * cc: akrzemi1 (added)
 * status:  assigned => closed
 * resolution:   => invalid

Comment:

 This breakage is intentional.

 In fact the previous behavior was inconsistent with `std::optional` and
 error-prone. Braces should deduce type `optional<T>`, not to `T`. For more
 details of why it was confusing, see here:
  http://stackoverflow.com/questions/40391244/difference-between-boost-

 optional-and-stdexperimental-optional-assignment/40677193#40677193

 Now the following puts the optional into no-value state:

 {{{
 boost::optional<S> so;
 so = {};
 }}}

 Just like `std::optional`.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12788#comment:5>
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