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111
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1 // PR c++/78131
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131
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2 // { dg-do compile { target c++17 } }
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111
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3
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4 template <typename TF>
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5 constexpr auto f(TF)
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6 {
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7 return [](auto...) constexpr { return true; };
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8 }
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9
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10 // Compiles and works as intended.
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11 template <typename T0>
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12 void ok_0(T0)
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13 {
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14 static_assert(f([](auto x) -> decltype(x){})(T0{}));
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15 }
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16
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17 // Compiles and works as intended.
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18 template <typename T0>
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19 void ok_1(T0)
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20 {
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21 constexpr auto a = f([](auto x) -> decltype(x){})(T0{});
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22 if constexpr(a) { }
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23 }
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24
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25 // Compile-time error!
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26 template <typename T0>
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27 void fail_0(T0)
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28 {
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29 if constexpr(f([](auto x) -> decltype(x){})(T0{})) { }
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30 }
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