Mercurial > hg > CbC > CbC_gcc
view gcc/testsuite/g++.dg/cpp0x/sfinae64.C @ 145:1830386684a0
gcc-9.2.0
author | anatofuz |
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date | Thu, 13 Feb 2020 11:34:05 +0900 |
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// PR c++/87748 // { dg-do compile { target c++11 } } template <class T> T&& declval(); template <bool B, class T> struct enable_if; template <class T> struct enable_if <true, T> { typedef T type; }; struct true_type { static const bool value = true; }; struct false_type { static const bool value = false; }; struct string { string (const char *p); }; /// Template to map all type arguments to void, useful for SFINAE, see also WG21 N3911. template<class...> using void_t = void; /// REQUIRES<value> - Simplified version of enable_if<> to use SFINAE in function templates. template<bool value> using REQUIRES = typename ::enable_if<value, bool>::type; /// DerivesString<T> - Check if @a T is of type 'string'. template<class T> struct DerivesString { static const int value = __is_same_as (T, string); }; /// Has__aida_visit__<T,Visitor> - Check if @a T provides a member template __aida_visit__<>(Visitor). template<class, class, class = void> struct Has__aida_visit__ : false_type {}; template<class T, class V> struct Has__aida_visit__<T, V, void_t< decltype (declval<T>().template __aida_visit__<V> (*(V*) 0)) >> : true_type {}; struct Foo { template<class V> void __accept__ (V*); }; /// Base template for Visitor classes, dispatches operator() to visit_<type>() methods. template<class DerivedVisitor> class VisitorDispatcher { DerivedVisitor* derived () { return static_cast<DerivedVisitor*> (this); } protected: typedef const char* Name; ///< Member name argument type for visit() methods. public: // dispatch for calls like: visitor (field, "field"); template<class A, REQUIRES< (!Has__aida_visit__<A, DerivedVisitor>::value) > = true> void operator() (A &a, Name n) { return derived()->visit_string (a, n); } }; class PspecVisitor : public VisitorDispatcher<PspecVisitor> { public: void visit_string (::string &a, Name name); }; int main (int argc, char *argv[]) { #ifdef WITHASSERT // define this to fix g++-8.1.1 static_assert (Has__aida_visit__<string, PspecVisitor>::value == false, ""); #endif PspecVisitor v; string str ("A string"); v (str, "some_string"); static_assert (Has__aida_visit__<string, PspecVisitor>::value == false, ""); return 0; } // g++ -std=gnu++14 -Wall -O2 aidavisit.cc && ./a.out