> Are you arguing for Solution D? Or are you proposing some new solution E? I > can't tell.
I suspect that I’m arguing for Solution B, but it’s hard to tell because it’s not described in enough detail in the Wiki. > Easy > > type instance WrapL ToolPass t = ... > > What am I missing? This assumes that `WrapL` is an open type family. In this case, there’s no problem. The merge request description has the following definition of WrapL: type instance WrapL p (f :: * -> *) where WrapL (GhcPass p) f = Located (f (GhcPass p)) WrapL p f = f p type LPat p = WrapL p Pat That wouldn’t be extensible. However, if WrapL is open, then Solution D sounds good to me. - Vlad > On 28 Oct 2019, at 13:20, Simon Peyton Jones <[email protected]> wrote: > > Vlad > > Are you arguing for Solution D? Or are you proposing some new solution E? I > can't tell. > > > | As to merge request !1970, it isn’t good to special-case GhcPass in a > | closed type family, making other tools second-class citizens. Let’s say I > | have `MyToolPass`, how would I write an instance of `WrapL` for it? > > Easy > > type instance WrapL ToolPass t = ... > > What am I missing? > > Simon > > | -----Original Message----- > | From: Vladislav Zavialov <[email protected]> > | Sent: 28 October 2019 10:07 > | To: Simon Peyton Jones <[email protected]> > | Cc: [email protected] > | Subject: Re: Handling source locations in HsSyn via TTG > | > | I care about this, and I maintain my viewpoint described in > | https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmail.has > | kell.org%2Fpipermail%2Fghc-devs%2F2019- > | February%2F017080.html&data=02%7C01%7Csimonpj%40microsoft.com%7C06c859 > | d8bc0f48c73cb208d75b8e895c%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C63 > | 7078540055975603&sdata=FhkqfWGXaNX%2Fz4IiCcvoVCyzVsSAlyz6Y1dxEGUjX9I%3 > | D&reserved=0 > | > | I’m willing to implement this. > | > | As to merge request !1970, it isn’t good to special-case GhcPass in a > | closed type family, making other tools second-class citizens. Let’s say I > | have `MyToolPass`, how would I write an instance of `WrapL` for it? > | > | - Vlad > | > | > On 28 Oct 2019, at 12:31, Simon Peyton Jones via ghc-devs <ghc- > | [email protected]> wrote: > | > > | > Friends > | > > | > As you know > | > > | > • We are trying to use “Trees That Grow” (TTG) to move HsSyn towards > | a situation in which GHC is merely a client of a generic HsSyn data type > | that can be used by clients other than GHC. > | > • One sticking point has been the question of attaching source > | locations. We used to have a “ping-pong” style, in which very node is > | decorated with a source location, but that’s a bit more awkward in TTG. > | > • This wiki page outlines some choices, while ticket #15495 has a > | lot of discussion. > | > • HEAD embodies Solution A. But it has the disadvantage that the > | type system doesn’t enforce locations to be present at all. That has > | undesirable consequences (eg ticket #17330) > | > • The proposal is to move to Solution D on that page; you can see > | how it plays out in MR !1970. > | > • (I think Solutions B and C are non-starters by comparison.) > | > If you care, please check out the design and the MR. We can change > | later, of course, but doing so changes a lot of code, including client > | code, so we’d prefer not to. > | > > | > Let’s try to converge by the end of the week. > | > > | > Thanks > | > > | > Simon > | > > | > > | > > | > > | > > | > _______________________________________________ > | > ghc-devs mailing list > | > [email protected] > | > > | https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmail.hask > | ell.org%2Fcgi-bin%2Fmailman%2Flistinfo%2Fghc- > | devs&data=02%7C01%7Csimonpj%40microsoft.com%7C06c859d8bc0f48c73cb208d7 > | 5b8e895c%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637078540055975603&a > | mp;sdata=CRYEYmjuAYYIhoAeTPbi%2FctCiWmkIjL6pKUTBgVBwo8%3D&reserved=0 > _______________________________________________ ghc-devs mailing list [email protected] http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
