Make Lint/RedundantWithIndex cop aware of offset argument

Follow up of rubocop#4796 (comment).

Actually, it is only `with_index` method that accepts an offset argument.
`with_with_index` method doesn't accept offset argument.
However, I think that the same AST will be low maintenance cost.

CHANGELOG.md

@@ -13,6 +13,7 @@
 
 * [#4888](https://github.com/bbatsov/rubocop/pull/4888): Improve offense message of `Style/StderrPuts`. ([@jaredbeck][])
 * [#4886](https://github.com/bbatsov/rubocop/issues/4886): Fix false offense for Style/CommentedKeyword. ([@michniewicz][])
+* [#4977](https://github.com/bbatsov/rubocop/pull/4977): Make `Lint/RedundantWithIndex` cop aware of offset argument. ([@koic][])
 
 ### New features
 

lib/rubocop/cop/lint/redundant_with_index.rb

@@ -33,7 +33,7 @@ class RedundantWithIndex < Cop
         def_node_matcher :redundant_with_index?, <<-PATTERN
           (block
             $(send
-              _ {:each_with_index :with_index})
+              _ {:each_with_index :with_index} ...)
             (args
               (arg _))
             ...)
@@ -51,7 +51,7 @@ def autocorrect(node)
               if send.method_name == :each_with_index
                 corrector.replace(send.loc.selector, 'each')
               else
-                corrector.remove(send.loc.selector)
+                corrector.remove(with_index_range(send))
                 corrector.remove(send.loc.dot)
               end
             end
@@ -69,7 +69,7 @@ def message(node)
         end
 
         def with_index_range(send)
-          range_between(send.loc.selector.begin_pos, send.loc.selector.end_pos)
+          range_between(send.loc.selector.begin_pos, send.source.length)
         end
       end
     end

spec/rubocop/cop/lint/redundant_with_index_spec.rb

@@ -19,6 +19,13 @@
     RUBY
   end
 
+  it 'registers an offense when using `ary.each.with_index(1) { |v| v }`' do
+    expect_offense(<<-RUBY.strip_indent)
+      ary.each.with_index(1) { |v| v }
+               ^^^^^^^^^^^^^ Remove redundant `with_index`.
+    RUBY
+  end
+
   it 'registers an offense when using `ary.each_with_object([]).with_index ' \
      '{ |v| v }`' do
     expect_offense(<<-RUBY.strip_indent)
@@ -39,6 +46,12 @@
     expect(new_source).to eq 'ary.each { |v| v }'
   end
 
+  it 'autocorrects to ary.each from ary.each.with_index(1)' do
+    new_source = autocorrect_source('ary.each.with_index(1) { |v| v }')
+
+    expect(new_source).to eq 'ary.each { |v| v }'
+  end
+
   it 'autocorrects to ary.each from ary.each_with_object([]).with_index' do
     new_source = autocorrect_source('ary.each_with_object([]) { |v| v }')