If requested info about some operator, ie (+) :info (+) is working as expected:

> :i (+)
class Num a where
  (+) :: a -> a -> a
  ...
  	-- Defined in ‘GHC.Num’
infixl 6 +

When additional space character is there :info (+ ) it won't parse:

> :i (+ )

<interactive>:1:3: error:
    parse error (possibly incorrect indentation or mismatched brackets)

Note that the same thing is working with :type so its strange it doesn't use the same parser in both places:

> :t (+ )
(+ ) :: Num a => a -> a -> a