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1 // PR c++/85149
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2 // { dg-do run { target c++17 } }
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3
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4 template <typename T> struct is_void { static constexpr bool value = false; };
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5 template <> struct is_void<void> { static constexpr bool value = true; };
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6
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7 template<typename S, typename T>
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8 constexpr decltype(auto) pipeline(S source, T target)
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9 {
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10 return [=](auto... args)
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11 {
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12 if constexpr(false
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13 && is_void<decltype(source(args...))>::value)
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14 {
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15 source(args...);
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16 return target();
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17 }
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18 else
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19 {
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20 return target(source(args...));
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21 }
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22 };
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23 }
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24
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25 int main() {
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26 int i = 10;
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27 int j = 42;
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28 auto p = pipeline([&]{ return j; },
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29 [=](int val){ return val * i; });
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30 if (p() != 420)
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31 __builtin_abort();
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32 }
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