[ruby/irb] fix reserved words and completion for them

https://github.com/ruby/irb/commit/6184b227ad

lib/irb/completion.rb

@@ -17,11 +17,12 @@ module IRB
     # Set of reserved words used by Ruby, you should not use these for
     # constants or variables
     ReservedWords = %w[
+      __ENCODING__ __LINE__ __FILE__
       BEGIN END
       alias and
       begin break
       case class
-      def defined do
+      def defined? do
       else elsif end ensure
       false for
       if in
@@ -255,7 +256,7 @@ module IRB
 
       else
         candidates = eval("methods | private_methods | local_variables | instance_variables | self.class.constants", bind).collect{|m| m.to_s}
-        conditions |= ReservedWords
+        candidates |= ReservedWords
 
         if doc_namespace
           candidates.find{ |i| i == input }

test/irb/test_completion.rb

@@ -35,5 +35,17 @@ module TestIRB
     def test_complete_symbol_failure
       assert_nil(IRB::InputCompletor::PerfectMatchedProc.(":aiueo", bind: binding))
     end
+
+    def test_complete_reserved_words
+      candidates = IRB::InputCompletor.retrieve_completion_data("de", bind: binding)
+      %w[def defined?].each do |word|
+        assert_include candidates, word
+      end
+
+      candidates = IRB::InputCompletor.retrieve_completion_data("__", bind: binding)
+      %w[__ENCODING__ __LINE__ __FILE__].each do |word|
+        assert_include candidates, word
+      end
+    end
   end
 end