+ | ipvar '::' type { LL (HsPredTy (HsIParam (unLoc $1) $3)) }
+ | type { $1 }
+
+----------------------
+-- Notes for 'ctypedoc'
+-- It would have been nice to simplify the grammar by unifying `ctype` and
+-- ctypedoc` into one production, allowing comments on types everywhere (and
+-- rejecting them after parsing, where necessary). This is however not possible
+-- since it leads to ambiguity. The reason is the support for comments on record
+-- fields:
+-- data R = R { field :: Int -- ^ comment on the field }
+-- If we allow comments on types here, it's not clear if the comment applies
+-- to 'field' or to 'Int'. So we must use `ctype` to describe the type.