GHC-problem with parsing infix type synonyms - bug?

Hi I read from the type-extensions.html part of the GHC 6.2 manual: "After expanding type synonyms, GHC does validity checking on types, looking for the following mal-formedness which isn't detected simply by kind checking: ... Partially-applied type synonym." However, when entering:

infix 9 :-+-: type (f :-+-: g) t o1 o2 = Either (f t o1 o2) (g t o1 o2)

or simpler variations e.g. without brackets, except where no arguments are present after (f :-+-: g), I get parse errors (yes, _parse_) on this very line. Also, the above works for data, and the "lexical syntax is the same as that for data constructors" [someone had read this somewhere]. Best Wishes, Johan Glimming