friend blocking_kind tag_invoke()

in include/unifex/when_all.hpp [324:359]

• 33 lines of code
• 8 McCabe index (conditional complexity)

  friend blocking_kind tag_invoke(tag_t<blocking>, const sender& s) noexcept {
    bool alwaysInline = true;
    bool alwaysBlocking = true;
    bool neverBlocking =  false;

    auto handleBlockingStatus = [&](blocking_kind kind) noexcept {
      switch (kind) {
        case blocking_kind::never:
          neverBlocking = true;
          [[fallthrough]];
        case blocking_kind::maybe:
          alwaysBlocking = false;
          [[fallthrough]];
        case blocking_kind::always:
          alwaysInline = false;
          [[fallthrough]];
        case blocking_kind::always_inline:
          break;
      }
    };

    std::apply([&](const auto&... senders) {
      (void)std::initializer_list<int>{
        (handleBlockingStatus(blocking(senders)), 0)... };
    }, s.senders_);

    if (neverBlocking) {
      return blocking_kind::never;
    } else if (alwaysInline) {
      return blocking_kind::always_inline;
    } else if (alwaysBlocking) {
      return blocking_kind::always;
    } else {
      return blocking_kind::maybe;
    }
  }