Merge pull request #104 from koic/mark_unsafe_for_performance_casecmp

[Fix #101] Mark unsafe for `Performance/Casecmp` cop

CHANGELOG.md

@@ -9,6 +9,7 @@
 ### Changes
 
 * [#103](https://github.com/rubocop-hq/rubocop-performance/pull/103): **(BREAKING)** Drop support for Ruby 2.3. ([@koic][])
+* [#101](https://github.com/rubocop-hq/rubocop-performance/issues/101): Mark unsafe for `Performance/Casecmp` cop. ([@koic][])
 
 ## 1.5.2 (2019-12-25)
 

config/default.yml

@@ -26,6 +26,7 @@ Performance/Casecmp:
              Use `casecmp` rather than `downcase ==`, `upcase ==`, `== downcase`, or `== upcase`..
   Reference: 'https://github.com/JuanitoFatas/fast-ruby#stringcasecmp-vs-stringdowncase---code'
   Enabled: true
+  Safe: false
   VersionAdded: '0.36'
 
 Performance/ChainArrayAllocation:

lib/rubocop/cop/performance/casecmp.rb

@@ -5,6 +5,8 @@ module Cop
     module Performance
       # This cop identifies places where a case-insensitive string comparison
       # can better be implemented using `casecmp`.
+      # This cop is unsafe because `String#casecmp` and `String#casecmp?` behave
+      # differently when using Non-ASCII characters.
       #
       # @example
       #   # bad

manual/cops_performance.md

@@ -120,10 +120,12 @@ AutoCorrect | `false` | Boolean
 
 Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
 --- | --- | --- | --- | ---
-Enabled | Yes | Yes  | 0.36 | -
+Enabled | No | Yes  | 0.36 | -
 
 This cop identifies places where a case-insensitive string comparison
 can better be implemented using `casecmp`.
+This cop is unsafe because `String#casecmp` and `String#casecmp?` behave
+differently when using Non-ASCII characters.
 
 ### Examples