This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 112e. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
[Adopted at the February, 2016 meeting.]
According to 6.8 [basic.types] bullet 10.5.3, all the members of a class type must be of non-volatile literal types. This seems overly constraining for unions; it would seem to be sufficient if at least one of its non-static members were of a literal type.
Proposed resolution (September, 2015):
Change 6.8 [basic.types] bullet 10.5 as follows:
A type is a literal type if it is:
a possibly cv-qualified class type (Clause 11 [class]) that has all of the following properties:
it has a trivial destructor,
it is an aggregate type (9.4.2 [dcl.init.aggr]) or has at least one constexpr constructor or constructor template that is not a copy or move constructor,
all of its non-static data members and base classes are of non-volatile literal types.