Reference (section label): [class.union.anon]

Issue description:

Currently [class.union.anon]p2 says:

Each member-declaration in the member-specification of an anonymous union shall either define one or more public non-static data members or be a static_assert-declaration.

This prohibits empty declarations in anonymous unions, i.e.

struct A { union {int x;;} u; }; //ok
struct B { union {int y;;}; }; //error

I do not see any motivation for this discrepancy.

Suggested resolution:

Modify the quoted sentence:

Each member-declaration in the member-specification of an anonymous union shall either define one or more public non-static data members, be an empty-declaration or be a static_assert-declaration .