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.
typeid expressions can never be constant, whether or not the operand is a polymorphic class type. The result of the expression is a reference, and the typeinfo class that the reference refers to is polymorphic, with a virtual destructor - it can never be a literal type.
Rationale (July, 2009):
The intent of this specification was that the address of such a typeinfo object could be treated as an address constant and thus usable in constant initialization (contrary to the statement in the comment, the result of typeid is an lvalue, not a reference).