Ensure that expression do not contain aggregate functions

include/sqlpp11/count.h

@@ -51,7 +51,6 @@ namespace sqlpp
 
 
 		static_assert(is_noop<Flag>::value or std::is_same<distinct_t, Flag>::value, "count() used with flag other than 'distinct'");
-		static_assert(is_expression_t<Expr>::value, "count() requires a sql expression as argument");
 
 		struct _name_t
 		{
@@ -100,7 +99,6 @@ namespace sqlpp
 	template<typename T>
 		auto count(T t) -> count_t<noop, wrap_operand_t<T>>
 		{
-			static_assert(not contains_aggregate_function_t<wrap_operand_t<T>>::value, "count() cannot be used on an aggregate function");
 			static_assert(is_expression_t<wrap_operand_t<T>>::value, "count() requires an expression as argument");
 			return { t };
 		}
@@ -108,7 +106,6 @@ namespace sqlpp
 	template<typename T>
 		auto count(const distinct_t&, T t) -> count_t<distinct_t, wrap_operand_t<T>>
 		{
-			static_assert(not contains_aggregate_function_t<wrap_operand_t<T>>::value, "count() cannot be used on an aggregate function");
 			static_assert(is_expression_t<wrap_operand_t<T>>::value, "count() requires an expression as argument");
 			return { t };
 		}

include/sqlpp11/max.h

@@ -39,8 +39,6 @@ namespace sqlpp
 		using _traits = make_traits<value_type_of<Expr>, tag::is_expression, tag::is_named_expression>;
 		using _recursive_traits = make_recursive_traits<Expr, aggregate_function>;
 
-		static_assert(is_expression_t<Expr>::value, "max() requires a value expression as argument");
-
 		struct _name_t
 		{
 			static constexpr const char* _get_name() { return "MAX"; }
@@ -83,8 +81,7 @@ namespace sqlpp
 	template<typename T>
 		auto max(T t) -> max_t<wrap_operand_t<T>>
 		{
-			static_assert(not contains_aggregate_function_t<wrap_operand_t<T>>::value, "max() cannot be used on an aggregate function");
+			static_assert(is_expression_t<wrap_operand_t<T>>::value, "max() requires an expression as argument");
-			static_assert(is_expression_t<wrap_operand_t<T>>::value, "max() requires a value expression as argument");
 			return { t };
 		}
 

include/sqlpp11/min.h

@@ -39,8 +39,6 @@ namespace sqlpp
 		using _traits = make_traits<value_type_of<Expr>, tag::is_expression, tag::is_named_expression>;
 		using _recursive_traits = make_recursive_traits<Expr, aggregate_function>;
 
-		static_assert(is_expression_t<Expr>::value, "min() requires a value expression as argument");
-
 		struct _name_t
 		{
 			static constexpr const char* _get_name() { return "MIN"; }
@@ -83,8 +81,7 @@ namespace sqlpp
 	template<typename T>
 		auto min(T t) -> min_t<wrap_operand_t<T>>
 		{
-			static_assert(not contains_aggregate_function_t<wrap_operand_t<T>>::value, "min() cannot be used on an aggregate function");
+			static_assert(is_expression_t<wrap_operand_t<T>>::value, "min() requires an expression as argument");
-			static_assert(is_expression_t<wrap_operand_t<T>>::value, "min() requires a value expression as argument");
 			return { t };
 		}
 

include/sqlpp11/type_traits.h

@@ -68,6 +68,23 @@ namespace sqlpp
 	template<typename T>
 	using column_spec_can_be_null_t = typename detail::column_spec_can_be_null_impl<T>::type;
 
+	namespace tag
+	{
+		struct is_expression{};
+	};
+	namespace detail
+	{
+		template<typename T, typename Enable = void>
+		struct is_expression_impl { using type = std::false_type; };
+		template<typename T>
+		struct is_expression_impl<T, typename std::enable_if<
+					detail::is_element_of<tag::is_expression, typename T::_traits::_tags>::value
+					and not detail::is_element_of<tag::contains_aggregate_function, typename T::_recursive_traits::_tags>::value
+					>::type> { using type = std::true_type; };
+	}
+	template<typename T>
+	using is_expression_t = typename detail::is_expression_impl<T>::type;
+
 #define SQLPP_VALUE_TRAIT_GENERATOR(name) \
 	namespace tag\
 	{\
@@ -94,7 +111,6 @@ namespace sqlpp
 		detail::is_element_of<tag::is_floating_point, typename T::_traits::_tags>::value>;
 	SQLPP_VALUE_TRAIT_GENERATOR(is_text);
 	SQLPP_VALUE_TRAIT_GENERATOR(is_wrapped_value);
-	SQLPP_VALUE_TRAIT_GENERATOR(is_expression);
 	SQLPP_VALUE_TRAIT_GENERATOR(is_named_expression);
 	SQLPP_VALUE_TRAIT_GENERATOR(is_multi_expression);
 	SQLPP_VALUE_TRAIT_GENERATOR(is_alias);

test_constraints/CMakeLists.txt

@@ -24,7 +24,8 @@ function(test_constraint name pattern)
 
 endfunction(test_constraint)
 
-test_constraint(count_of_count "cannot be used on an aggregate function")
+test_constraint(count_of_count "requires an expression as argument")
+test_constraint(max_of_max "requires an expression as argument")
 test_constraint(no_conversion_operator_if_null_not_trivial "int i = row.alpha")
 test_constraint(require_insert "required column is missing")
 test_constraint(must_not_insert "one assignment is prohibited")

test_constraints/max_of_max.cpp

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2013-2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification, 
+ * are permitted provided that the following conditions are met:
+ * 
+ *  * Redistributions of source code must retain the above copyright notice, 
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright notice, 
+ *    this list of conditions and the following disclaimer in the documentation 
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Sample.h"
+#include "MockDb.h"
+#include <sqlpp11/functions.h>
+#include <iostream>
+
+MockDb db;
+
+int main()
+{
+	test::TabBar t;
+
+	max(max(t.alpha));
+}