Proposed resolution:

This wording is relative to N4842.

1. Modify [locale] as indicated:

   […]
   ~locale(); // not virtual
   const locale& operator=(const locale& other) noexcept;
   template<class Facet> locale combine(const locale& other) const;
   […]
   

2. Modify [locale.cons] as indicated:

   const locale& operator=(const locale& other) noexcept;
   

   -14- Effects: Creates a copy of other, replacing the current value.

   -15- Returns: *this.

[ 2019-12-21 Issue Prioritization ]

Priority to 3 after reflector discussion based on the observation that we have implementation divergence.

Curiously, locale's copy assignment operator currently returns const locale&. As Casey Carter noted in microsoft/STL#268, this is:

• Weird!

• The only occurrence in the entire Standard Library.

• Preventing locale from satisfying std::copyable.

We aren't aware of any reason for this to be const. (I observe that this hasn't changed since N1804 on 2005-04-27 and probably goes back to C++98; I suspect that when this was originally specified, copy assignment operators were relatively new, and conventions for them weren't rigorously followed.)