From 1b86d90136efb98c7b331a84ca163587307a49af Mon Sep 17 00:00:00 2001
From: "yuuji.yaginuma" <yuuji.yaginuma@gmail.com>
Date: Thu, 17 May 2018 17:32:27 +0900
Subject: Enable `Performance/UnfreezeString` cop
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

In Ruby 2.3 or later, `String#+@` is available and `+@` is faster than `dup`.

```ruby
# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  gem "benchmark-ips"
end

Benchmark.ips do |x|
  x.report('+@') { +"" }
  x.report('dup') { "".dup }
  x.compare!
end
```

```
$ ruby -v benchmark.rb
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]
Warming up --------------------------------------
                  +@   282.289k i/100ms
                 dup   187.638k i/100ms
Calculating -------------------------------------
                  +@      6.775M (± 3.6%) i/s -     33.875M in   5.006253s
                 dup      3.320M (± 2.2%) i/s -     16.700M in   5.032125s

Comparison:
                  +@:  6775299.3 i/s
                 dup:  3320400.7 i/s - 2.04x  slower

```
---
 .rubocop.yml | 3 +++
 1 file changed, 3 insertions(+)

(limited to '.rubocop.yml')

diff --git a/.rubocop.yml b/.rubocop.yml
index a673e6ba83..c6c8d8ca00 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -208,3 +208,6 @@ Performance/EndWith:
 
 Performance/RegexpMatch:
   Enabled: true
+
+Performance/UnfreezeString:
+  Enabled: true
-- 
cgit v1.2.3