From 4bfd993c3039fca23176896eac6e21688ce2d8a0 Mon Sep 17 00:00:00 2001
From: Jan Zajic <jan.zajic@corpus.cz>
Date: Sat, 9 Nov 2019 21:12:23 +0100
Subject: [PATCH] change byte_slice(Int) ArgumentError->IndexError when out of
 range

---
 spec/std/string_spec.cr | 12 ++++++++++++
 src/string.cr           |  6 ++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/spec/std/string_spec.cr b/spec/std/string_spec.cr
index 8ace564ab67f..ececca3c7766 100644
--- a/spec/std/string_spec.cr
+++ b/spec/std/string_spec.cr
@@ -229,6 +229,18 @@ describe "String" do
     it "gets byte_slice with negative index" do
       "hello".byte_slice(-2, 3).should eq("lo")
     end
+
+    it "gets byte_slice(Int) with with start out of bounds" do
+      expect_raises(IndexError) do
+        "hello".byte_slice(10)
+      end
+    end
+
+    it "gets byte_slice(Int) with with start out of bounds" do
+      expect_raises(IndexError) do
+        "hello".byte_slice(-10)
+      end
+    end
   end
 
   describe "to_i" do
diff --git a/src/string.cr b/src/string.cr
index dac1b98bf53f..7dd2e1b18c86 100644
--- a/src/string.cr
+++ b/src/string.cr
@@ -953,8 +953,10 @@ class String
     end
   end
 
-  def byte_slice(start : Int)
-    byte_slice start, bytesize - start
+  def byte_slice(start : Int) : String
+    count = bytesize - start
+    raise IndexError.new if start > 0 && count < 0
+    byte_slice start, count
   end
 
   # Returns a substring starting from the *start* byte.