Yes this is annoying. The thing is that with the first constructor only we'd get (LHsSigWcType Id) after type checking, but we don't have such a thing. `HsTypes` are typechecked to `Types`. Perhaps we could have (LHsSigWcType (StopAtRenamer d)) where type family StopAtRenamer a where StopAtRenamer Id = Name StopAtRenamer x = x If this pattern happened a lot it might be worth it. But I think this is the only occurrence. Better ideas welcome. Simon | -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Alan | & Kim Zimmerman | Sent: 19 December 2015 13:15 | To: ghc-devs@haskell.org | Subject: ExprWithTySigOut | | At the moment HsExpr includes the following two constructors | | | ExprWithTySig | (LHsExpr id) | (LHsSigWcType id) | | | ExprWithTySigOut -- Post typechecking | (LHsExpr id) | (LHsSigWcType Name) -- Retain the signature, | -- as HsSigType Name, for | -- round-tripping purposes | | I do not understand why we need the second one, which hard-codes Name | instead of id. | | There are a couple of places where there is an XXXOut variant with | hard coded Name parameter, and these complicate creating any kind of | custom class intended to work on a parameterised AST as it ripples out | and forces Name instances of it everywhere. | | Perhaps we should introduce HsExprLR id id to cope with renaming? | | Alan | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmail.h | askell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc- | devs&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7c70b008fd4c5b43b | 3915e08d308766f7d%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=MB%2fBX | bBIUeYFlOOH5PGXV27wJpZRNKcHJV%2fTQmfI%2f%2bE%3d