Enumerable#find_all return Enumerator if non block given

mrbgems/mruby-enumerator/test/enumerator.rb

@@ -448,6 +448,10 @@ assert 'Enumerable#map' do
   assert_equal [[1,0],[4,1],[9,4]], c
 end
 
+assert 'Enumerable#find_all' do
+  assert_equal [[3,4]], [[1,2],[3,4],[5,6]].find_all.each{ |i| i[1] == 4 }
+end
+
 assert 'Array#each_index' do
   a = [1,2,3]
   b = a.each_index

mrblib/enum.rb

@@ -144,6 +144,8 @@ module Enumerable
   #
   # ISO 15.3.2.2.8
   def find_all(&block)
+    return to_enum :find_all unless block_given?
+
     ary = []
     self.each{|*val|
       ary.push(val.__svalue) if block.call(*val)