Hello devs, I am trying to modify GHC's parser to allow the following syntax in types: a -> @m b but my naive attempt was unsuccessful: type :: { LHsType GhcPs } : btype { $1 } | btype '->' PREFIX_AT btype ctype ... For example when I try to parse the following code (and turn on the lexer debug log): test :: a -> @m b test = undefined I get the following token: ITvarid "test" token: ITdcolon NormalSyntax token: ITvarid "a" token: ITrarrow NormalSyntax token: ITtypeApp token: ITvarid "m" token: ITvarid "b" token: ITsemi Parse.hs:2:1: error: parse error (possibly incorrect indentation or mismatched brackets) | 2 | test = undefined I don't have much experience with hacking on the parser so I'm likely missing something obvious. Could someone please point at what I might be doing wrong? Thanks in advance. Cheers, Csongor