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2740. constexpr optional<T>::operator->

Section: 22.5.3.6 [optional.observe] Status: C++17 Submitter: Agustín K-ballo Bergé Opened: 2016-07-02 Last modified: 2017-07-30

Priority: 0

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Discussion:

optional<T>::operator->s are constrained to be constexpr functions only when T is not a type with an overloaded unary operator&. This constrain comes from the need to use addressof (or a similar mechanism), and the inability to do so in a constant expression in C++14. Given that addressof is now constexpr, this constrain is no longer needed.

[2016-07 Chicago]

Monday: P0 - tentatively ready

Proposed resolution:

This wording is relative to N4594.

1. Modify [optional.object.observe] as indicated:

   constexpr T const* operator->() const;
   constexpr T* operator->();
   

   -1- Requires: *this contains a value.

   -2- Returns: val.

   -3- Throws: Nothing.

   -4- Remarks: Unless T is a user-defined type with overloaded unary operator&, tThese functions shall be constexpr functions.