Should raise TypeError instead of NoMethodError

mrbgems/mruby-enum-ext/mrblib/enum.rb

@@ -768,7 +768,12 @@ module Enumerable
 
   def zip(*arg, &block)
     result = block ? nil : []
-    arg = arg.map{|a|a.to_a}
+    arg = arg.map do |a|
+      unless a.respond_to?(:to_a)
+        raise TypeError, "wrong argument type #{a.class} (must respond to :to_a)"
+      end
+      a.to_a
+    end
 
     i = 0
     self.each do |*val|

mrbgems/mruby-enum-ext/test/enum.rb

@@ -170,6 +170,8 @@ assert("Enumerable#zip") do
   ret = []
   assert_equal nil, a.zip([1, 2], [8]) { |i| ret << i }
   assert_equal [[4, 1, 8], [5, 2, nil], [6, nil, nil]], ret
+
+  assert_raise(TypeError) { [1].zip(1) }
 end
 
 assert("Enumerable#to_h") do