what would u call defined? in ruby

defined? in ruby

=begin
<raggi> 	anyone know if there's a term that describes what the defined? keyword does?	12:44 PM
 <raggi> 	i asked my guys today if they could describe waht it does, and was ofc met mostly with silence, i know i can describe it, but i'm not sure i know of a term that means the same thing	12:44 PM
 <dkannan> 	raggi: type of slot - not a term as such	12:46 PM
 <raggi> 	dkannan: that's not what defined? is	12:46 PM
 <raggi> 	dkannan: try doing: defined?((1;1))	12:46 PM
 <dkannan> 	raggi: ok	12:47 PM
 <dkannan> 	raggi: some more: defined?(1); defined?(Fixnum); defined?(Object.new); defined?(o = Object.new);	12:51 PM
 <dkannan> 	raggi: it is like how the interpreter sees the world.	12:56 PM
 <dkannan> 	raggi: how does interpreter dry-run sound?	12:56 PM
 <raggi> 	i think the closest term is partial evaluation
=end

ruby-1.9.2-p0 > defined? foo
 => nil 
ruby-1.9.2-p0 > defined? foo #not defined
 => nil 
ruby-1.9.2-p0 > defined?((1;1))
 => "expression" 
ruby-1.9.2-p0 > defined?((1;1))
 => "expression" 
ruby-1.9.2-p0 > defined? 1
 => "expression" 
ruby-1.9.2-p0 > defined? Fixnum
 => "constant" 
ruby-1.9.2-p0 > defined? 1
 => "expression" 
ruby-1.9.2-p0 > defined? Object.new
 => "method" 
ruby-1.9.2-p0 > defined?(o = Object.new)
 => "assignment" 
ruby-1.9.2-p0 > o #o has been defined but it is nil
 => nil 
ruby-1.9.2-p0 > o = Object.new
 => #<Object:0x00000001181040> 
ruby-1.9.2-p0 > defined?(o)
 => "local-variable" 
ruby-1.9.2-p0 > defined? FOO
 => nil 
ruby-1.9.2-p0 > FOO
NameError: uninitialized constant Object::FOO
	from (irb):9
	from /home/deepak/.rvm/rubies/ruby-1.9.2-p0/bin/irb:17:in `<main>'
ruby-1.9.2-p0 > FOO = 10
ruby-1.9.2-p0 > defined? FOO
 => "constant" 

what does the rubyspec say?

defined?(o = Object.new) #assignment
defined?(o) #local-variable

seems like a bug (raggi) as the AST now has the variable 'o'. It is not without side-effects