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Fixes to futures #505

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merged 5 commits into from
Nov 8, 2022
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@sean-parent sean-parent commented Oct 22, 2022

Fixed unnecessary copies of copyable result types when futures are used as rvalues. Propagating exceptions for move-only types are now scheduled on the executor (I'm not sure why they were not scheduled before). Added copy() algorithm to utility.hpp to explicitly copy objects. Added docs and tests.

Fixed unnecessary copies of copyable result types when futures are used as rvalues.
Propagating exceptions for move-only types are now scheduled on the executor (I'm not sure why they were not scheduled before).
Added `copy()` algorithm to utility.hpp to explicitly copy objects.
/// Returns a copy of the argument. Used to pass an lvalue to function taking an rvalue or to
/// copy a type with an `explicit` copy-constructor.
template <typename T>
T copy(const T& a) {
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@fosterbrereton fosterbrereton Nov 8, 2022

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Previously you gave an implementation of copy to be:

template <typename T>
constexpr std::decay_t<T> copy(T&& value) noexcept(
    noexcept(std::decay_t<T>{static_cast<T&&>(value)})) {
  static_assert(!std::is_same<std::decay_t<T>, T>::value, "explicit copy of rvalue.");
  return std::decay_t<T>{static_cast<T&&>(value)};
}

What's changed between now and then that's resulted in the greatly simplified variant?

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Moving to use the above - nothing changed other than my memory of writing the above...

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@fosterbrereton fosterbrereton left a comment

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I had one question about your copy implementation. Other than that I don't see anything wrong with this PR.

@sean-parent sean-parent merged commit d722622 into stlab:main Nov 8, 2022
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2 participants