clean and refactor

lib/melon/passes/method_compiler.rb

@@ -32,7 +32,7 @@ module Melon
         w = Vm::Tree::CallSite.new()
         puts "receiver #{statement}"
         w.name = name
-        w.arguments = process(args)
+        w.arguments = process(args) || []
         w.receiver = process(receiver)
         w
       end

lib/melon/ruby_method.rb

@@ -6,6 +6,9 @@ module Melon
 
     def initialize(name , args_type , locals_type , source )
       @name , @args_type , @locals_type , @source = name , args_type, locals_type , source
+      raise "Name must be symbol" unless name.is_a?(Symbol)
+      raise "args_type must be type" unless args_type.is_a?(Parfait::Type)
+      raise "locals_type must be type" unless locals_type.is_a?(Parfait::Type)
     end
 
     def normalize_source