Add argument_type? method to make it easy to recognize argument nodes

Closes rubocop#11

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Changes
+
+* [#11](https://github.com/rubocop-hq/rubocop-ast/issues/11): Add `argument_type?` method to make it easy to recognize argument nodes. ([@tejasbubane][])
+
 ## 0.0.3 (2020-05-15)
 
 ### Changes

lib/rubocop/ast/node.rb

@@ -53,6 +53,7 @@ class Node < Parser::AST::Node # rubocop:disable Metrics/ClassLength
                     yield].freeze
       OPERATOR_KEYWORDS = %i[and or].freeze
       SPECIAL_KEYWORDS = %w[__FILE__ __LINE__ __ENCODING__].freeze
+      ARGUMENT_TYPES = %i[arg optarg restarg kwarg kwoptarg kwrestarg blockarg].freeze
 
       # @see https://www.rubydoc.info/gems/ast/AST/Node:initialize
       def initialize(type, children = [], properties = {})
@@ -456,6 +457,10 @@ def argument?
         parent&.send_type? && parent.arguments.include?(self)
       end
 
+      def argument_type?
+        ARGUMENT_TYPES.include?(type)
+      end
+
       def boolean_type?
         true_type? || false_type?
       end

spec/rubocop/ast/node_spec.rb

@@ -347,4 +347,16 @@ def used?
       end
     end
   end
+
+  describe '#argument_type?' do
+    let(:src) { ' bar { |a, b = 42, *c, d: 42, **e| nil }' }
+
+    it 'returns true for all argument types' do
+      node.children[1].children.each do |arg|
+        expect(arg.argument_type?).to eq(true)
+      end
+
+      expect(node.argument_type?).to eq(false)
+    end
+  end
 end