Returned to older version of IsStreamable

- this time based on code from Martin Moene
https://gist.github.com/martinmoene/5418947#file-insertionopdetector-cpp

include/internal/catch_sfinae.hpp

@@ -11,8 +11,6 @@
 // Try to detect if the current compiler supports SFINAE
 #include "catch_compiler_capabilities.h"
 
-#ifdef CATCH_SFINAE
-
 namespace Catch {
     
     struct TrueType {
@@ -26,6 +24,8 @@ namespace Catch {
         char sizer[2];
     };
 
+#ifdef CATCH_SFINAE
+
     template<bool> struct NotABooleanExpression;
 
     template<bool c> struct If : NotABooleanExpression<c> {};
@@ -35,10 +35,10 @@ namespace Catch {
     template<int size> struct SizedIf;
     template<> struct SizedIf<sizeof(TrueType)> : TrueType {};
     template<> struct SizedIf<sizeof(FalseType)> : FalseType {};
+
+#endif // CATCH_SFINAE
     
 } // end namespace Catch
 
-#endif // CATCH_SFINAE
-
 #endif // TWOBLUECUBES_CATCH_SFINAE_HPP_INCLUDED
 

include/internal/catch_tostring.hpp

@@ -20,11 +20,10 @@
 #endif
 
 namespace Catch {
+namespace Detail {
 
 #ifdef CATCH_SFINAE
 
-namespace Detail {
-
     template<typename T>
     class IsStreamInsertableHelper {
         template<int N> struct TrueIfSizeable : TrueType {};
@@ -40,53 +39,47 @@ namespace Detail {
     template<typename T>
     struct IsStreamInsertable : IsStreamInsertableHelper<T>::type {};
 
-    template<typename T>
-    void toStream( std::ostream& os, T const& value, typename IsStreamInsertable<T>::Enable* = 0 ) {
-        os << value;
-    }
-
-    template<typename T>
-    void toStream( std::ostream& os, T const&, typename IsStreamInsertable<T>::Disable* = 0 ) {
-        os << "{?}";
-    }
-   
-}
-
-template<typename T>
-struct StringMaker {
-    static std::string convert( T const& value ) {
-        std::ostringstream oss;
-        Detail::toStream( oss, value );
-        return oss.str();
-    }
-};
-
 #else
 
-namespace Detail {
+    struct BorgType {
+        template<typename T> BorgType( T const& );
+    };
+  
+    TrueType& testStreamable( std::ostream& );
+    FalseType testStreamable( FalseType );
+    
+    FalseType operator<<( std::ostream const&, BorgType const& );
 
-    struct NonStreamable {
-        template<typename T> NonStreamable( const T& ){}
+    template<typename T>
+    struct IsStreamInsertable {
+        static std::ostream &s;
+        static T const &t;
+        enum { value = sizeof( testStreamable(s << t) ) == sizeof( TrueType ) };
+    };
+    
+#endif
+
+    template<bool C>
+    struct StringMakerBase {
+        template<typename T>
+        static std::string convert( T const& ) { return "{?}"; }
+    };
+
+    template<>
+    struct StringMakerBase<true> {
+        template<typename T>
+        static std::string convert( T const& _value ) {
+            std::ostringstream oss;
+            oss << _value;
+            return oss.str();
+        }
     };
     
 } // end namespace Detail
 
-// If the type does not have its own << overload for ostream then
-// this one will be used instead
-inline std::ostream& operator << ( std::ostream& ss, Detail::NonStreamable ){
-    return ss << "{?}";
-}
-
 template<typename T>
-struct StringMaker {
-    static std::string convert( T const& value ) {
-        std::ostringstream oss;
-        oss << value;
-        return oss.str();
-    }
-};
-
-#endif
+struct StringMaker :
+    Detail::StringMakerBase<Detail::IsStreamInsertable<T>::value> {};
 
 
 template<typename T>

projects/SelfTest/TrickyTests.cpp

@@ -342,11 +342,9 @@ struct Awkward
     operator int() const { return 7; }
 };
 
-// This now works with GCC/ Clang usinh SFINAE
-// Uncomment when it works on all compilers that are tested
-//TEST_CASE( "non streamable", "" )
-//{
-//    Awkward awkward;
-//    std::string s = Catch::toString( awkward );
-//    REQUIRE( s == "7" ); // This is ambiguous without SFINAE
-//}
+TEST_CASE( "non streamable - with conv. op", "" )
+{
+    Awkward awkward;
+    std::string s = Catch::toString( awkward );
+    REQUIRE( s == "7" );
+}