Test.y

{
module Main where
}

%error { parseError }
%errorhandlertype explist
%monad { Either String }
%name parseFoo
%tokentype { Char }

%token
  char { $$ }

%%

Foo :: { String }
  : char {% Left "error" }
  | char { "good" }

{
parseError :: ([Char], [String]) -> Either String a
parseError (got, expected) = Left $ show got <> ", " <> show expected

main :: IO ()
main = print $ parseFoo "x"

-- unused rules: 1
-- reduce/reduce conflicts: 1
-- Right "good"
}