From 32fdcafb1a1ce8ab95a74d6049d0e167541b0c88 Mon Sep 17 00:00:00 2001
From: Eugene Kenny <elkenny@gmail.com>
Date: Sun, 20 Sep 2020 19:44:55 +0100
Subject: [PATCH] Ignore non-integer ranges in Style/RandomWithOffset

This cop only works correctly for ranges with integer bounds.
---
 CHANGELOG.md                                  |  1 +
 lib/rubocop/cop/style/random_with_offset.rb   |  6 ++---
 .../cop/style/random_with_offset_spec.rb      | 24 +++++++++++++++++++
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a481ed9e3d7..75c67127dc5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@
 * [#8739](https://github.com/rubocop-hq/rubocop/issues/8739): Fix an error for `Lint/UselessTimes` when using empty block argument. ([@koic][])
 * [#8742](https://github.com/rubocop-hq/rubocop/issues/8742): Fix some assignment counts for `Metrics/AbcSize`. ([@marcandre][])
 * [#8750](https://github.com/rubocop-hq/rubocop/pull/8750): Fix an incorrect auto-correct for `Style/MultilineWhenThen` when line break for multiple condidate values of `when` statement. ([@koic][])
+* [#8754](https://github.com/rubocop-hq/rubocop/pull/8754): Fix an error for `Style/RandomWithOffset` when using a range with non-integer bounds. ([@eugeneius][])
 
 ### Changes
 
diff --git a/lib/rubocop/cop/style/random_with_offset.rb b/lib/rubocop/cop/style/random_with_offset.rb
index 4da28c90e52..644269a7181 100644
--- a/lib/rubocop/cop/style/random_with_offset.rb
+++ b/lib/rubocop/cop/style/random_with_offset.rb
@@ -36,7 +36,7 @@ class RandomWithOffset < Base
             (send
               {nil? (const {nil? cbase} :Random) (const {nil? cbase} :Kernel)}
               :rand
-              {int irange erange}))
+              {int (irange int int) (erange int int)}))
         PATTERN
 
         def_node_matcher :rand_op_integer?, <<~PATTERN
@@ -44,7 +44,7 @@ class RandomWithOffset < Base
             (send
               {nil? (const {nil? cbase} :Random) (const {nil? cbase} :Kernel)}
               :rand
-              {int irange erange})
+              {int (irange int int) (erange int int)})
             {:+ :-}
             int)
         PATTERN
@@ -54,7 +54,7 @@ class RandomWithOffset < Base
             (send
               {nil? (const {nil? cbase} :Random) (const {nil? cbase} :Kernel)}
               :rand
-              {int irange erange})
+              {int (irange int int) (erange int int)})
             {:succ :pred :next})
         PATTERN
 
diff --git a/spec/rubocop/cop/style/random_with_offset_spec.rb b/spec/rubocop/cop/style/random_with_offset_spec.rb
index e7bc14a1693..64530575735 100644
--- a/spec/rubocop/cop/style/random_with_offset_spec.rb
+++ b/spec/rubocop/cop/style/random_with_offset_spec.rb
@@ -258,6 +258,30 @@
     RUBY
   end
 
+  it 'does not register an offense when using rand(irange) + offset with a non-integer range value' do
+    expect_no_offenses(<<~RUBY)
+      rand(0..limit) + 1
+    RUBY
+  end
+
+  it 'does not register an offense when using offset - rand(erange) with a non-integer range value' do
+    expect_no_offenses(<<~RUBY)
+      1 - rand(0...limit)
+    RUBY
+  end
+
+  it 'does not register an offense when using rand(irange).succ with a non-integer range value' do
+    expect_no_offenses(<<~RUBY)
+      rand(0..limit).succ
+    RUBY
+  end
+
+  it 'does not register an offense when using rand(erange).pred with a non-integer range value' do
+    expect_no_offenses(<<~RUBY)
+      rand(0...limit).pred
+    RUBY
+  end
+
   it 'does not register an offense when using range with double dots' do
     expect_no_offenses('rand(1..6)')
   end