From befc9896d0f699163e6c252771ef3f4234b48f3b Mon Sep 17 00:00:00 2001
From: Nathan Sashihara <21227491+n8sh@users.noreply.github.com>
Date: Tue, 9 Jan 2018 15:05:59 -0500
Subject: [PATCH] Fix Issue 18217: Don't repeatedly call unpredictableSeed to
 initialize rndGen

Explanation: https://github.com/dlang/phobos/pull/5788#discussion_r146110307
---
 std/random.d | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/std/random.d b/std/random.d
index 5741b8e868c..4a493f78585 100644
--- a/std/random.d
+++ b/std/random.d
@@ -1357,8 +1357,8 @@ A singleton instance of the default random number generator
     static bool initialized;
     if (!initialized)
     {
-        static if (isSeedable!(Random, typeof(map!((a) => unpredictableSeed)(repeat(0)))))
-            result.seed(map!((a) => unpredictableSeed)(repeat(0)));
+        static if (isSeedable!(Random, ReturnType!unpredictableSeed))
+            result.seed(unpredictableSeed); // Avoid unnecessary copy.
         else
             result = Random(unpredictableSeed);
         initialized = true;