Proposed resolution (February, 2016):

Change 7.7 [expr.const] paragraph 5 as follows:

A constant expression is either a glvalue core constant expression whose value refers to an entity that is a permitted result of a constant expression (as defined below), or a prvalue core constant expression whose value is an object where, for that object and its subobjects satisfies the following constraints:

• if the value is an object of class type, each non-static data member of reference type refers to an entity that is a permitted result of a constant expression, and

• if the object or subobject value is of pointer type, it contains the address of an object with static storage duration, the address past the end of such an object (7.6.6 [expr.add]), the address of a function, or a null pointer value., and

• if the value is an object of class or array type, each subobject satisfies these constraints for the value.

An entity is a permitted result of a constant expression if...

[Adopted at the February, 2016 meeting.]

According to 7.7 [expr.const] paragraph 5,

A constant expression is either a glvalue core constant expression whose value... or a prvalue core constant expression whose value is an object where...

Since an integer literal is prvalue that is not an object, this definition does not allow it to be a constant expression.