From e05e049c6942198c5be49101d7caeef9a1b00119 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 17 Nov 2015 16:38:34 +1100
Subject: [PATCH] cast: ensure real<->int or size reduction in trunc_cast

---
 cast.hpp | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/cast.hpp b/cast.hpp
index c0d57aab..90e8129d 100644
--- a/cast.hpp
+++ b/cast.hpp
@@ -71,9 +71,17 @@ sign_cast (const U u)
 /// assert if the value cannot be cast loslessly from U to T, else return the
 /// converted value.Note: this is only a debug-time check and is compiled out
 /// in optimised builds.
-
-template <typename T, typename U>
-T
+template <
+    typename T,
+    typename U
+>
+std::enable_if_t<
+    // either we're casting from real to integer
+    !std::is_floating_point<T>::value && std::is_floating_point<U>::value
+    // or we're reducing the size of the type
+    || sizeof (T) < sizeof (U),
+    T
+>
 trunc_cast (U u)
 {
     auto t = static_cast<T> (u);