Merge pull request #8957 from marcandre/comp_doc

Improve doc for MultipleComparison

docs/modules/ROOT/pages/cops_style.adoc

@@ -6074,7 +6074,8 @@ end
 |===
 
 This cop checks against comparing a variable with multiple items, where
-`Array#include?` could be used instead to avoid code repetition.
+`Array#include?`, `Set#include?` or a `case` could be used instead
+to avoid code repetition.
 It accepts comparisons of multiple method calls to avoid unnecessary method calls
 by default. It can be configured by `AllowMethodComparison` option.
 
@@ -6089,6 +6090,17 @@ foo if a == 'a' || a == 'b' || a == 'c'
 # good
 a = 'a'
 foo if ['a', 'b', 'c'].include?(a)
+
+VALUES = Set['a', 'b', 'c'].freeze
+# elsewhere...
+foo if VALUES.include?(a)
+
+case foo
+when 'a', 'b', 'c' then foo
+# ...
+end
+
+# accepted (but consider `case` as above)
 foo if a == b.lightweight || a == b.heavyweight
 ----
 

lib/rubocop/cop/style/multiple_comparison.rb

@@ -4,7 +4,8 @@ module RuboCop
   module Cop
     module Style
       # This cop checks against comparing a variable with multiple items, where
-      # `Array#include?` could be used instead to avoid code repetition.
+      # `Array#include?`, `Set#include?` or a `case` could be used instead
+      # to avoid code repetition.
       # It accepts comparisons of multiple method calls to avoid unnecessary method calls
       # by default. It can be configured by `AllowMethodComparison` option.
       #
@@ -16,6 +17,17 @@ module Style
       #   # good
       #   a = 'a'
       #   foo if ['a', 'b', 'c'].include?(a)
+      #
+      #   VALUES = Set['a', 'b', 'c'].freeze
+      #   # elsewhere...
+      #   foo if VALUES.include?(a)
+      #
+      #   case foo
+      #   when 'a', 'b', 'c' then foo
+      #   # ...
+      #   end
+      #
+      #   # accepted (but consider `case` as above)
       #   foo if a == b.lightweight || a == b.heavyweight
       #
       # @example AllowMethodComparison: true (default)