With the proposed resolution of 2067, this no longer selects the copy constructor:

std::packaged_task<void()> p1;
std::packaged_task<void()> p2(p1);

Instead this constructor is a better match:

template <class F>
 explicit packaged_task(F&& f);

This attempts to package a packaged_task, which internally tries to copy p2, which fails because the copy constructor is deleted. For at least one implementation the resulting error message is much less helpful than the expected "cannot call deleted function" because it happens after instantiating several more templates rather than in the context where the constructor is called.

I believe the solution is to constrain to the template constructors so the template argument F cannot be deduced as (possibly cv) packaged_task& or packaged_task. It could be argued this constraint is already implied because packaged_task is not copyable and the template constructors require that "invoking a copy of f shall behave the same as invoking f".

Daniel points out that the variadic constructor of std::thread described in [thread.thread.constr] has a similar problem and suggests a similar wording change, which has been integrated below.

An alternative is to declare thread(thread&) and packaged_task(packaged_task&) as deleted.