Added missing requires clause to the get() function of the type_safe_union.

It will now cause a compile time error if called inappropriately.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403382

dlib/type_safe_union/type_safe_union_kernel.h

@@ -301,7 +301,26 @@ namespace dlib
             }
         }
 
-        template <typename T> T& get() { construct<T>();  return *reinterpret_cast<T*>(mem.get()); }
+        template <typename T> 
+        T& get(
+        ) 
+        { 
+            // ERROR: You are trying to get a type of object that isn't currently
+            // in the type_safe_union.
+            COMPILE_TIME_ASSERT(( is_same_type<T,T1>::value ||
+                                 is_same_type<T,T2>::value ||
+                                 is_same_type<T,T3>::value ||
+                                 is_same_type<T,T4>::value ||
+                                 is_same_type<T,T5>::value ||
+                                 is_same_type<T,T6>::value ||
+                                 is_same_type<T,T7>::value ||
+                                 is_same_type<T,T8>::value ||
+                                 is_same_type<T,T9>::value ||
+                                 is_same_type<T,T10>::value 
+                                    ));
+
+            construct<T>();  return *reinterpret_cast<T*>(mem.get()); 
+        }
 
     };
 

dlib/type_safe_union/type_safe_union_kernel_abstract.h

@@ -120,6 +120,8 @@ namespace dlib
         T& get(
         );
         /*!
+            requires
+                - T must be one of the types given to this object's template arguments
             ensures
                 - #is_empty() == false
                 - #contains<T>() == true