Added portable static asserts for (dynamic) join.on()

Also removed inaccessible code for adding more conditions to on()
dynamically. If someone should ever want that, he/she should use
dynamic_where(), I guess.

include/sqlpp11/cross_join.h

@@ -53,6 +53,35 @@ namespace sqlpp
   template <typename Lhs, typename Rhs>
   using check_cross_join_t = typename check_cross_join<Lhs, Rhs>::type;
 
+  SQLPP_PORTABLE_STATIC_ASSERT(assert_join_consist_of_cross_join_and_on_t,
+                               "join has to consist of a cross_join and a join condition");
+  SQLPP_PORTABLE_STATIC_ASSERT(assert_join_no_table_dependencies_t, "joined tables must not depend on other tables");
+  SQLPP_PORTABLE_STATIC_ASSERT(assert_join_on_no_foreign_table_dependencies_t,
+                               "on() condition must not depend on other tables");
+
+  template <typename CrossJoin, typename On>
+  struct check_join
+  {
+    using type = static_combined_check_t<
+        static_check_t<is_cross_join_t<CrossJoin>::value, assert_join_consist_of_cross_join_and_on_t>,
+        static_check_t<is_on_t<On>::value, assert_join_consist_of_cross_join_and_on_t>,
+        static_check_t<required_tables_of<CrossJoin>::size::value == 0, assert_join_no_table_dependencies_t>,
+        static_check_t<detail::is_subset_of<required_tables_of<On>, provided_tables_of<CrossJoin>>::value,
+                       assert_join_on_no_foreign_table_dependencies_t>>;
+  };
+
+  template <typename CrossJoin, typename On>
+  using check_join_t = typename check_join<CrossJoin, On>::type;
+
+  template <typename CrossJoin, typename Expr>
+  struct check_join_on
+  {
+    using type = static_combined_check_t<check_on_t<Expr>, check_join_t<CrossJoin, on_t<Expr>>>;
+  };
+
+  template <typename CrossJoin, typename Expr>
+  using check_join_on_t = typename check_join_on<CrossJoin, Expr>::type;
+
   template <typename CrossJoin, typename On>
   struct join_t;
 
@@ -73,16 +102,16 @@ namespace sqlpp
     static_assert(required_tables_of<cross_join_t>::size::value == 0, "joined tables must not depend on other tables");
 
     template <typename Expr>
-    auto on(Expr expr) -> join_t<cross_join_t, on_t<void, Expr>>
+    auto on(Expr expr) -> typename std::conditional<check_join_on_t<cross_join_t, Expr>::value,
+                                                    join_t<cross_join_t, on_t<Expr>>,
+                                                    bad_statement>::type
     {
-      static_assert(is_expression_t<Expr>::value, "argument is not an expression in on()");
-
-      static_assert(is_boolean_t<Expr>::value, "argument is not a boolean expression in on()");
+      check_join_on_t<cross_join_t, Expr>::_();
 
-      return {*this, {expr, {}}};
+      return {*this, {expr}};
     }
 
-    auto unconditionally() -> join_t<cross_join_t, on_t<void, unconditional_t>>
+    auto unconditionally() -> join_t<cross_join_t, on_t<unconditional_t>>
     {
       return {*this, {}};
     }

include/sqlpp11/dynamic_cross_join.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2016, Roland Bock
+ * Copyright (c) 2016-2016, Roland Bock
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modification,
@@ -32,6 +32,32 @@
 
 namespace sqlpp
 {
+  SQLPP_PORTABLE_STATIC_ASSERT(assert_dynamic_join_consist_of_cross_join_and_on_t,
+                               "dynamic join has to consist of a dynamic cross_join and a join condition");
+  SQLPP_PORTABLE_STATIC_ASSERT(assert_dynamic_join_no_table_dependencies_t,
+                               "dynamically joined tables must not depend on other tables");
+
+  template <typename CrossJoin, typename On>
+  struct check_dynamic_join
+  {
+    using type = static_combined_check_t<
+        static_check_t<is_dynamic_cross_join_t<CrossJoin>::value, assert_dynamic_join_consist_of_cross_join_and_on_t>,
+        static_check_t<is_on_t<On>::value, assert_dynamic_join_consist_of_cross_join_and_on_t>,
+        static_check_t<required_tables_of<CrossJoin>::size::value == 0, assert_dynamic_join_no_table_dependencies_t>>;
+  };
+
+  template <typename CrossJoin, typename On>
+  using check_dynamic_join_t = typename check_dynamic_join<CrossJoin, On>::type;
+
+  template <typename CrossJoin, typename Expr>
+  struct check_dynamic_join_on
+  {
+    using type = static_combined_check_t<check_on_t<Expr>, check_dynamic_join_t<CrossJoin, on_t<Expr>>>;
+  };
+
+  template <typename CrossJoin, typename Expr>
+  using check_dynamic_join_on_t = typename check_dynamic_join_on<CrossJoin, Expr>::type;
+
   template <typename CrossJoin, typename On>
   struct dynamic_join_t;
 
@@ -49,15 +75,16 @@ namespace sqlpp
                   "joined tables must not depend on other tables");
 
     template <typename Expr>
-    auto on(Expr expr) -> dynamic_join_t<dynamic_cross_join_t, on_t<void, Expr>>
+    auto on(Expr expr) -> typename std::conditional<check_dynamic_join_on_t<dynamic_cross_join_t, Expr>::value,
+                                                    dynamic_join_t<dynamic_cross_join_t, on_t<Expr>>,
+                                                    bad_statement>::type
     {
-      static_assert(is_expression_t<Expr>::value, "argument is not a boolean expression in on()");
-      static_assert(is_boolean_t<Expr>::value, "argument is not a boolean expression in on()");
+      check_dynamic_join_on_t<dynamic_cross_join_t, Expr>::_();
 
-      return {*this, {expr, {}}};
+      return {*this, {expr}};
     }
 
-    auto unconditionally() -> dynamic_join_t<dynamic_cross_join_t, on_t<void, unconditional_t>>
+    auto unconditionally() -> dynamic_join_t<dynamic_cross_join_t, on_t<unconditional_t>>
     {
       return {*this, {}};
     }

include/sqlpp11/dynamic_join.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2015, Roland Bock
+ * Copyright (c) 2016-2016, Roland Bock
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modification,

include/sqlpp11/join.h

@@ -42,13 +42,6 @@ namespace sqlpp
     using _provided_tables = provided_tables_of<CrossJoin>;
     using _required_tables = detail::make_difference_set_t<required_tables_of<On>, _provided_tables>;
 
-    static_assert(is_cross_join_t<CrossJoin>::value, "lhs argument for join() has to be a table or join");
-    static_assert(is_on_t<On>::value, "invalid on expression in join().on()");
-
-    static_assert(required_tables_of<CrossJoin>::size::value == 0, "joined tables must not depend on other tables");
-    static_assert(detail::is_subset_of<required_tables_of<On>, provided_tables_of<CrossJoin>>::value,
-                  "on() condition must not depend on other tables");
-
     template <typename T>
     auto join(T t) const -> decltype(::sqlpp::join(*this, t))
     {

include/sqlpp11/on.h

@@ -34,76 +34,57 @@
 
 namespace sqlpp
 {
-  template <typename Database, typename Expression>
+  SQLPP_PORTABLE_STATIC_ASSERT(assert_on_is_expression_t, "argument is not an expression in on()");
+  SQLPP_PORTABLE_STATIC_ASSERT(assert_on_is_boolean_expression_t, "argument is not a boolean expression in on()");
+
+  template <typename Expr>
+  struct check_on
+  {
+    using type = static_combined_check_t<static_check_t<is_expression_t<Expr>::value, assert_on_is_expression_t>,
+                                         static_check_t<is_boolean_t<Expr>::value, assert_on_is_boolean_expression_t>>;
+  };
+
+  template <typename Expr>
+  using check_on_t = typename check_on<Expr>::type;
+
+  template <typename Expression>
   struct on_t
   {
     using _traits = make_traits<no_value_t, tag::is_on>;
     using _nodes = detail::type_vector<Expression>;
 
-    using _is_dynamic = is_database<Database>;
-
-    template <typename Expr>
-    void add(Expr expr)
-    {
-      static_assert(_is_dynamic::value, "on::add() must not be called for static on()");
-      static_assert(is_expression_t<Expr>::value, "invalid expression argument in on::add()");
-      using _serialize_check = sqlpp::serialize_check_t<typename Database::_serializer_context_t, Expr>;
-      _serialize_check::_();
-
-      using ok = logic::all_t<_is_dynamic::value, is_expression_t<Expr>::value, _serialize_check::type::value>;
-
-      _add_impl(expr, ok());  // dispatch to prevent compile messages after the static_assert
-    }
-
-  private:
-    template <typename Expr>
-    void _add_impl(Expr expr, const std::true_type&)
-    {
-      return _dynamic_expressions.emplace_back(expr);
-    }
-
-    template <typename Expr>
-    void _add_impl(Expr expr, const std::false_type&);
-
-  public:
     Expression _expression;
-    interpretable_list_t<Database> _dynamic_expressions;
   };
 
   template <>
-  struct on_t<void, unconditional_t>
+  struct on_t<unconditional_t>
   {
     using _traits = make_traits<no_value_t, tag::is_on>;
     using _nodes = detail::type_vector<>;
   };
 
   template <typename Context>
-  struct serializer_t<Context, on_t<void, unconditional_t>>
+  struct serializer_t<Context, on_t<unconditional_t>>
   {
     using _serialize_check = consistent_t;
-    using T = on_t<void, unconditional_t>;
+    using T = on_t<unconditional_t>;
 
     static Context& _(const T&, Context& context)
     {
       return context;
     }
   };
 
-  template <typename Context, typename Database, typename... Expressions>
-  struct serializer_t<Context, on_t<Database, Expressions...>>
+  template <typename Context, typename Expression>
+  struct serializer_t<Context, on_t<Expression>>
   {
-    using _serialize_check = serialize_check_of<Context, Expressions...>;
-    using T = on_t<Database, Expressions...>;
+    using _serialize_check = serialize_check_of<Context, Expression>;
+    using T = on_t<Expression>;
 
     static Context& _(const T& t, Context& context)
     {
-      if (sizeof...(Expressions) == 0 and t._dynamic_expressions.empty())
-        return context;
       context << " ON (";
       serialize(t._expression, context);
-      if (not t._dynamic_expressions.empty())
-        context << " AND ";
-      interpret_list(t._dynamic_expressions, " AND ", context);
       context << " )";
       return context;
     }