On GCC 14.2.1 and libstdc++, during await_resume this comparison in taskbase.h:

Q_ASSERT(this->mAwaitedCoroutine != nullptr);

seems to hit an infinite recursion in std::expected here:

template<typename _Up>
  friend constexpr bool
  operator==(const expected& __x, const _Up& __v)
  // FIXME: noexcept(noexcept(bool(*__x == __v)))
  { return __x.has_value() && bool(*__x == __v); }

for this template instance:

std::operator==<std::coroutine_handle<QCoro::detail::TaskPromise<std::expected<A, B>>>>

where A and B are types used in my code.

I am not sure where the left-hand std::expected comes from, but it seems like the multiple implicit conversions that need to happen here (coroutine_handle to coroutine_handle<>, nullptr_t to coroutine_handle<>) cause sufficient ambiguity for GCC to perform the comparison in an unexpected way.

This is fixed if I change this to an implicit conversion to bool instead, as is done elsewhere in this file.