From 54da39a2df6fd230d2c888e1d54adb29780983ee Mon Sep 17 00:00:00 2001
From: Dmitry Olshansky <dmitry.olsh@gmail.com>
Date: Thu, 16 Mar 2017 16:57:34 +0100
Subject: [PATCH] Make std.algo.copy CTFE-able

---
 std/algorithm/mutation.d | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/std/algorithm/mutation.d b/std/algorithm/mutation.d
index 5cb4f125ed9..f1aa9ee4769 100644
--- a/std/algorithm/mutation.d
+++ b/std/algorithm/mutation.d
@@ -375,7 +375,7 @@ if (areCopyCompatibleArrays!(SourceRange, TargetRange))
     assert(tlen >= slen,
             "Cannot copy a source range into a smaller target range.");
 
-    immutable overlaps = () @trusted {
+    immutable overlaps = __ctfe || () @trusted {
         return source.ptr < target.ptr + tlen &&
                target.ptr < source.ptr + slen; }();
 
@@ -486,6 +486,14 @@ $(HTTP sgi.com/tech/stl/copy_backward.html, STL's copy_backward'):
     assert(dest == [0, 0, 1, 2, 4]);
 }
 
+// Test CTFE copy.
+@safe unittest
+{
+    enum c = copy([1,2,3], [4,5,6,7]);
+    assert(c == [7]);
+}
+
+
 @safe unittest
 {
     import std.algorithm.iteration : filter;