Merge pull request #1099 from ashmaroli/stash-types-private-constant

Use a private constant to stash token-types

lib/liquid/parser.rb

@@ -44,11 +44,14 @@ module Liquid
       tok[0] == type
     end
 
+    SINGLE_TOKEN_EXPRESSION_TYPES = [:string, :number].freeze
+    private_constant :SINGLE_TOKEN_EXPRESSION_TYPES
+
     def expression
       token = @tokens[@p]
       if token[0] == :id
         variable_signature
-      elsif [:string, :number].include? token[0]
+      elsif SINGLE_TOKEN_EXPRESSION_TYPES.include? token[0]
         consume
       elsif token.first == :open_round
         consume