This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 112c. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
The relationship between when an expression is potentially evaluated, especially with respect to contexts requiring constant expressions, and non-type template arguments is not clear and should be clarified. In particular, it seems that these contexts should be potentially-evaluated.
See also issue 1378.
Additional note, January, 2012:
Further discussion indicates that this is not a defect and should be closed as such.
Notes from the February, 2012 meeting:
CWG determined that the current wording is clear enough that an instantiation is required whenever it affects the semantics of the program.