maths: use SFINAE for round_to instead of assert

maths.hpp

@@ -89,8 +89,18 @@ rootsquare [[gnu::pure]] (T a, T b);
 //-----------------------------------------------------------------------------
 // Rounding
 template <typename T, typename U>
-typename std::common_type<T, U>::type
+inline
-round_to [[gnu::pure]] (T value, U size);
+typename std::common_type<
+    std::enable_if_t<std::is_integral<T>::value,T>,
+    std::enable_if_t<std::is_integral<U>::value,U>
+>::type
+round_to [[gnu::const]] (T value, U size)
+{
+    if (value % size == 0)
+        return value;
+
+    return value + (size - value % size);
+}
 
 
 template <typename T>

maths.ipp

@@ -22,16 +22,6 @@
 
 #include <type_traits>
 
-//-----------------------------------------------------------------------------
-template <typename T, typename U>
-typename std::common_type<T,U>::type
-round_to (T value, U size) {
-    static_assert (std::is_integral<T>::value, "align requires integral types");
-    static_assert (std::is_integral<U>::value, "align requires integral types");
-
-    return divup (value, size) * size;
-}
-
 
 //-----------------------------------------------------------------------------
 template <typename T>