Prefer "using" over "typedef"

doc/conversion.qbk

@@ -150,10 +150,10 @@ This includes C++ built-in pointers, `std::shared_ptr`,
     class Banana : public Fruit {};
 
     // Use one of these:
-    typedef Fruit* FruitPtr;
+    using FruitPtr = Fruit*;
-    typedef std::shared_ptr<Fruit> FruitPtr;
+    using FruitPtr = std::shared_ptr<Fruit>;
-    typedef boost::shared_ptr<Fruit> FruitPtr;
+    using FruitPtr = boost::shared_ptr<Fruit>;
-    typedef boost::intrusive_ptr<Fruit> FruitPtr;
+    using FruitPtr = boost::intrusive_ptr<Fruit>;
 
     void f(FruitPtr fruit) {
       // ... logic which leads us to believe it is a banana

include/boost/implicit_cast.hpp

@@ -17,7 +17,7 @@ namespace detail {
 
 template<class T> struct icast_identity
 {
-    typedef T type;
+    using type = T;
 };
 
 } // namespace detail

include/boost/polymorphic_cast.hpp

@@ -113,7 +113,7 @@ namespace boost
         std::is_reference<Target>::value, Target
     >::type polymorphic_downcast(Source& x)
     {
-        typedef typename std::remove_reference<Target>::type* target_pointer_type;
+        using target_pointer_type = typename std::remove_reference<Target>::type*;
         return *boost::polymorphic_downcast<target_pointer_type>(
             std::addressof(x)
         );

test/implicit_cast.cpp

@@ -18,8 +18,8 @@ struct foo
     operator long() const { return 0; }
 };
 
-typedef type<long> long_type;
+using long_type = type<long>;
-typedef type<foo> foo_type;
+using foo_type = type<foo>;
 
 int main()
 {