From 568cd18b43fb2fe98a5eb62f06a00648450d7068 Mon Sep 17 00:00:00 2001
From: Ulrich Kuettler <kuettler@gmail.com>
Date: Tue, 17 Feb 2015 20:50:19 +0100
Subject: [PATCH] Fix Issue 13390 - Be explicit about non-empty input and fail
 early

Add unittest
---
 std/range/package.d | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/std/range/package.d b/std/range/package.d
index db9fc9ea557..5c4000df373 100644
--- a/std/range/package.d
+++ b/std/range/package.d
@@ -2473,6 +2473,8 @@ random access and also offers a constructor taking an initial position
 $(D index). $(D Cycle) works with static arrays in addition to ranges,
 mostly for performance reasons.
 
+Note: The input range must not be empty.
+
 Tip: This is a great way to implement simple circular buffers.
 */
 struct Cycle(R)
@@ -2698,6 +2700,7 @@ nothrow:
 Cycle!R cycle(R)(R input)
     if (isForwardRange!R && !isInfinite!R)
 {
+    assert(!input.empty);
     return Cycle!R(input);
 }
 
@@ -2713,6 +2716,7 @@ Cycle!R cycle(R)(R input)
 Cycle!R cycle(R)(R input, size_t index = 0)
     if (isRandomAccessRange!R && !isInfinite!R)
 {
+    assert(!input.empty);
     return Cycle!R(input, index);
 }
 
@@ -2890,6 +2894,14 @@ unittest //10845
     auto a = recurrence!q{a[n - 1] ~ a[n - 2]}("1", "0");
 }
 
+// Issue 13390
+unittest
+{
+    import std.exception;
+    import core.exception : AssertError;
+    assertThrown!AssertError(cycle([0, 1, 2][0..0]));
+}
+
 private alias lengthType(R) = typeof(R.init.length.init);
 
 /**