[MacPorts] #66646: qt5-qtwebengine: fatal error: 'optional' file not found

[MacPorts]

#66646: qt5-qtwebengine: fatal error: 'optional' file not found
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  Reporter:  mf2k             |      Owner:  MarcusCalhoun-Lopez
      Type:  defect           |     Status:  assigned
  Priority:  Normal           |  Milestone:
 Component:  ports            |    Version:  2.8.99
Resolution:                   |   Keywords:
      Port:  qt5-qtwebengine  |
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Comment (by kencu):

 I suspect it’s because builld sets std=c++14 but optional needs std=c++17.

 https://en.cppreference.com/w/cpp/utility/optional

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Ticket URL: <https://trac.macports.org/ticket/66646#comment:4>
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