expose expression_cache/string_scanner via attr_reader, skip regex in filter args without colon

lib/liquid/parse_context.rb

@@ -3,7 +3,7 @@
 module Liquid
   class ParseContext
     attr_accessor :locale, :line_number, :trim_whitespace, :depth
-    attr_reader :partial, :warnings, :error_mode, :environment
+    attr_reader :partial, :warnings, :error_mode, :environment, :expression_cache, :string_scanner
 
     def initialize(options = Const::EMPTY_HASH)
       @environment = options.fetch(:environment, Environment.default)

lib/liquid/variable.rb

@@ -143,8 +143,8 @@ module Liquid
 
       # Resolve the name expression
       expr_markup = markup.byteslice(name_start, name_end - name_start)
-      cache = parse_context.instance_variable_get(:@expression_cache)
-      ss = parse_context.instance_variable_get(:@string_scanner)
+      cache = parse_context.expression_cache
+      ss = parse_context.string_scanner
 
       if Expression::LITERALS.key?(expr_markup)
         @name = Expression::LITERALS[expr_markup]
@@ -300,7 +300,8 @@ module Liquid
       filter_args  = []
       keyword_args = nil
       unparsed_args.each do |a|
-        if (matches = a.match(JustTagAttributes))
+        # Fast check: keyword args must contain ':'
+        if a.include?(':') && (matches = a.match(JustTagAttributes))
           keyword_args           ||= {}
           keyword_args[matches[1]] = parse_context.parse_expression(matches[2])
         else