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131
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1 // { dg-do compile { target c++17 } }
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2 // { dg-options "-fconcepts" }
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111
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3
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4 // Check that we can evaluate constant requires-expressions
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5 // as constant expressions, for the curious case when they
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6 // appear within predicate constraints.
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7
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8 template<typename... Ts> struct variant { };
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9
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10 template<typename T>
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11 concept bool Streamable()
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12 {
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13 return requires (T t) { t; };
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14 }
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15
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16 template<typename T>
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17 concept bool Range()
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18 {
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19 return requires (T t) { t; };
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20 }
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21
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22 template<class T>
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23 requires Streamable<T>() and not Range<T>()
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24 void print(const T& x) { }
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25
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26 int main()
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27 {
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28 print("hello"); // { dg-error "cannot call" }
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29 }
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