+fds :: { [([RdrName], [RdrName])] }
+ : {- empty -} { [] }
+ | '|' fds1 { reverse $2 }
+
+fds1 :: { [([RdrName], [RdrName])] }
+ : fds1 ',' fd { $3 : $1 }
+ | fd { [$1] }
+
+fd :: { ([RdrName], [RdrName]) }
+ : varids0 '->' varids0 { (reverse $1, reverse $3) }
+
+varids0 :: { [RdrName] }
+ : {- empty -} { [] }
+ | varids0 tv_name { $2 : $1 }
+
+---------------------------------------------------