coroutine<>::push_type function starts without pushing

[valentin.milea@…]

According to coroutine2 docs: "In contrast to coroutine<>::pull_type, instantiating an coroutine<>::push_type does not pass the control of execution to coroutine-function - instead the first call of coroutine<>::push_type::operator() synthesizes a complementary coroutine<>::pull_type and passes it as reference to coroutine-function. "

So the function of a push-coroutine should never be entered unless at least one value is pushed. But the coroutine always tries to unwind in destructor and mistakenly resumes the function. Example attached.

This bug is present in coroutine2. Original coroutine library is unaffected.

[olli]

thx, fixed