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.
[Moved to DR at the April, 2013 meeting.]
Currently, literal class types can have mutable members. It is not clear whether that poses any particular problems with constexpr objects and constant expressions, and if so, what should be done about it.
Proposed resolution (February, 2012):
Change 7.7 [expr.const] paragraph 2 as follows:
an lvalue-to-rvalue conversion (7.3.2 [conv.lval]) unless it is applied to
a glvalue of integral or enumeration type that refers to a non-volatile const object with a preceding initialization, initialized with a constant expression, or
a glvalue of literal type that refers to a non-volatile object defined with constexpr, or that refers to a sub-object of such an object, or
a glvalue of literal type that refers to a non-volatile temporary object whose lifetime has not ended, initialized with a constant expression;