[ 2017-02-23, Jonathan comments and suggests wording ]

I don't think the Clause 17 wording in [res.on.functions] is sufficient to require that the delete expression is well-formed. A class-specific deallocation function ([class.free]) would not be covered by [res.on.functions] and so could throw:

struct Y { void operator delete(void*) noexcept(false) { throw 1; } };