Add `language_eval` method.

Library/Homebrew/cask/lib/hbc/cask.rb

@@ -11,7 +11,10 @@ module Hbc
       @token = token
       @sourcefile_path = sourcefile_path
       @dsl = dsl || DSL.new(@token)
-      @dsl.instance_eval(&block) if block_given?
+      if block_given?
+        @dsl.instance_eval(&block)
+        @dsl.language_eval
+      end
     end
 
     DSL::DSL_METHODS.each do |method_name|

Library/Homebrew/cask/lib/hbc/dsl.rb

@@ -100,30 +100,31 @@ module Hbc
     end
 
     def language(*args, &block)
-      @language ||= {}
-
       if !args.empty? && block_given?
         args.each do |arg|
           MacOS.languages.each_with_index do |l, index|
             string_or_regex = arg == :default ? %r{^en} : arg
             next unless l.match(string_or_regex)
-            next unless @language[:level].nil? || @language[:level] > index
+            next unless @language.nil? || @language[:level].nil? || @language[:level] > index
             @language = {
                           block: block,
                           level: index,
                         }
           end
         end
-
-        if args.include?(:default)
-          # :default has to be the last language block in order to assign return value of the selected `language` block to `@language`
-          @language = @language[:block].call
-        end
       else
+        language_eval
         @language
       end
     end
 
+
+    def language_eval
+      if @language.is_a?(Hash) && @language.key?(:block)
+        @language = @language[:block].call
+      end
+    end
+
     def url(*args, &block)
       url_given = !args.empty? || block_given?
       return @url unless url_given