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2805.void and reference type alternatives invariant,variant<> andindex()

Section: 22.6[variant], 22.6.3[variant.variant], 22.6.3.2[variant.ctor]Status:ResolvedSubmitter: SwitzerlandOpened: 2016-11-10Last modified: 2020-09-06

Priority:Not Prioritized

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Discussion:

Addresses CH 3, CH 4, CH 5, CH 6, CH 8

1. variant allows reference types as alternatives;optional explicitly forbids to be instantiated for reference types. This is inconsistent.

2. variant<int, void> should be as usable asvariant<int>.

3. variant<> should not have anindex() function.

4. Clarify the intended behavior ofvariant for alternative types that are references.

5. Clarifyvariant construction.

Proposed change:

1. Consider allowing reference types for both or none.

2. —

3. Consider specifying a specialization forvariant<>like:

   template<> class variant<> { public:   variant() = delete;   variant(const variant&) = delete;   variant& operator=(variant const&) = delete;};

4. Add a respective note.

5. Add a note thatvariant<> cannot be constructed.

[Issues Telecon 16-Dec-2016]

Resolved by the adoption ofP0501R0.

Proposed resolution: