From 7609a1c7c66031b1edd5c8aa2a3718c3b1481829 Mon Sep 17 00:00:00 2001
From: Dave Abrahams <dave@boostpro.com>
Date: Mon, 25 Nov 2002 22:03:42 +0000
Subject: [PATCH] Refactored; added static assertions against the specification
 of a default implementation

[SVN r16414]
---
 include/boost/python/def.hpp | 112 ++++++++++++++++-------------------
 1 file changed, 52 insertions(+), 60 deletions(-)

diff --git a/include/boost/python/def.hpp b/include/boost/python/def.hpp
index 5631fb56..8914818b 100644
--- a/include/boost/python/def.hpp
+++ b/include/boost/python/def.hpp
@@ -18,15 +18,25 @@ namespace boost { namespace python {
 
 namespace detail
 {
-  template <class Fn, class A1>
-  void
-  dispatch_def(
-      void const*,
-      char const* name,
-      Fn fn,
-      A1 const& a1)
+  namespace error
   {
-      def_helper<A1> helper(a1);
+    // Compile-time error messages
+    template <bool> struct multiple_functions_passed_to_def;
+    template <> struct multiple_functions_passed_to_def<false> { typedef char type; };
+  }
+  
+  //
+  // def_from_helper --
+  //
+  // Use a def_helper to define a regular wrapped function in the current scope.
+  template <class F, class Helper>
+  void def_from_helper(
+      char const* name, F const& fn, Helper const& helper)
+  {
+      // Must not try to use default implementations except with method definitions.
+      typedef typename error::multiple_functions_passed_to_def<
+          Helper::has_default_implementation
+          >::type assertion;
       
       detail::scope_setattr_doc(
           name, boost::python::make_function(
@@ -35,41 +45,37 @@ namespace detail
               , helper.keywords())
           , helper.doc()
           );
-    }
+  }
 
-    template <class Fn, class A1, class A2>
-    void dispatch_def(
-        void const*,
-        char const* name,
-        Fn fn,
-        A1 const& a1,
-        A2 const& a2)
-    {
-        def_helper<A1,A2> helper(a1,a2);
+  //
+  // These two overloads discriminate between def() as applied to
+  // regular functions and def() as applied to the result of
+  // BOOST_PYTHON_FUNCTION_OVERLOADS(). The final argument is used to
+  // discriminate.
+  //
+  template <class Fn, class A1>
+  void
+  def_maybe_overloads(
+      char const* name
+      , Fn fn
+      , A1 const& a1
+      , ...)
+  {
+      detail::def_from_helper(name, fn, def_helper<A1>(a1));
+  }
 
-        detail::scope_setattr_doc(
-            name, python::make_function(
-                fn
-                , helper.policies()
-                , helper.keywords())
-            , helper.doc()
-            );
-    }
-
-    template <class StubsT, class SigT>
-    void dispatch_def(
-        detail::overloads_base const*,
-        char const* name,
-        SigT sig,
-        StubsT const& stubs)
-    {
-        //  convert sig to a type_list (see detail::get_signature in signature.hpp)
-        //  before calling detail::define_with_defaults.
-
-        scope current;
-        detail::define_with_defaults(
-            name, stubs, current, detail::get_signature(sig));
-    }
+  template <class StubsT, class SigT>
+  void def_maybe_overloads(
+      char const* name
+      , SigT sig
+      , StubsT const& stubs
+      , detail::overloads_base const*)
+  {
+      scope current;
+      
+      detail::define_with_defaults(
+          name, stubs, current, detail::get_signature(sig));
+  }
 }
 
 template <class Fn>
@@ -81,33 +87,19 @@ void def(char const* name, Fn fn)
 template <class Arg1T, class Arg2T>
 void def(char const* name, Arg1T arg1, Arg2T const& arg2)
 {
-    //  The arguments may be:
-    //      def(name, function)
-    //      def(name, function, policy)
-    //      def(name, function, doc_string)
-    //      def(name, signature, stubs)
-
-    detail::dispatch_def(&arg2, name, arg1, arg2);
+    detail::def_maybe_overloads(name, arg1, arg2, &arg2);
 }
 
-template <class Arg1T, class Arg2T, class Arg3T>
-void def(char const* name, Arg1T arg1, Arg2T const& arg2, Arg3T const& arg3)
+template <class F, class A1, class A2>
+void def(char const* name, F f, A1 const& a1, A2 const& a2)
 {
-    detail::dispatch_def(&arg2, name, arg1, arg2, arg3);
+    detail::def_from_helper(name, f, detail::def_helper<A1,A2>(a1,a2));
 }
 
 template <class F, class A1, class A2, class A3>
 void def(char const* name, F f, A1 const& a1, A2 const& a2, A3 const& a3)
 {
-    detail::def_helper<A1,A2,A3> helper(a1,a2,a3);
-
-    detail::scope_setattr_doc(
-        name, python::make_function(
-            f
-            , helper.policies()
-            , helper.keywords())
-        , helper.doc()
-        );
+    detail::def_from_helper(name, f, detail::def_helper<A1,A2,A3>(a1,a2,a3));
 }
 
 }} // namespace boost::python