Would it easier to send the diff to Phab? I don't think the git history will be particularly illuminating.
On Mon, Nov 17, 2014, at 07:45, Austin Seipp wrote: > This looks excellent! Thank you Adam and Eric for helping Iavor with > this. > > But I'm slightly confused by the git history since it seems to be > cluttered with a few merges, and it seems like Eric has pushed the > latest changes to all this. The branch is also a little bit behind > master too. > > Iavor, would you like to: > > 1) Incorporate all of the changes from Eric and Adam, > 2) Rebase your work on HEAD so we can read it in a digestible way? > > I still need to read over all the changes since my first review, since > Adam addressed them. The 7.10 branch is at the end of this week, but > this would be a really cool feature to have. > > Thanks! > > The branch for 7.10 is now the end of this week! It would be nice to get > this in > > On Sun, Nov 16, 2014 at 1:33 PM, Eric Seidel <e...@seidel.io> wrote: > > Hi Adam, > > > > I've made a few changes based on your branch. Specifically I've removed > > the call to runTcPlugins inside solveFlats, and have replaced it with > > a specific runTcPluginsGiven that runs in a loop inside solveFlatsGiven > > much like your runTcPluginsFinal runs inside solveFlatsWanted. I think > > this is a bit cleaner given that you've split the wanteds-solving out > > already. > > > > The changes are at https://github.com/gridaphobe/ghc/tree/wip/tc-plugins-els > > since I don't have commit access to GHC :) > > > > Iavor and I also have a question about your change to the last statement > > in solveFlatWanteds. You're putting the unsolved wanteds in a field > > called wc_flat, which suggests that they ought to be flattened. But > > the unsolved wanteds were just unflattened a few lines above! Is this > > a problem, or is the wc_flat field in need of a new name? :) > > > > Eric > > > > > >> On Nov 14, 2014, at 09:14, Adam Gundry <a...@well-typed.com> wrote: > >> > >> Thanks, Simon! I've been convinced that TcS is more than we need, and I > >> think the right thing to do is to (optionally) invoke the plugin after > >> the constraints have been unflattened anyway. I've just pushed a commit > >> to wip/tc-plugins-amg that does this. Iavor, Eric, your views on how > >> convenient this alternative is would be most welcome. I'm also wondering > >> if the plugin should be told how many times it has been called, to make > >> it easier to prevent infinite loops. > >> > >> I'm very keen to get this into 7.10, appropriately branded as a very > >> experimental feature. Austin, have I sufficiently addressed your > >> concerns about the hs-boot file and multiple flags? Is there anything > >> else we need, apart perhaps from tests and documentation, which I'll put > >> together next week? > >> > >> Thanks, > >> > >> Adam > >> > >> > >> On 12/11/14 11:16, Simon Peyton Jones wrote: > >>> Iavor, Adam, Eric > >>> > >>> > >>> > >>> I’m happy with the general direction of the plugins stuff, so I’m mostly > >>> going to leave it to you guys to plough ahead; but I am happy to respond > >>> to questions. > >>> > >>> > >>> > >>> * I still think it would be better to provide an escape hatch to the > >>> TcS, not merely the TcM, alongside the nice TcPluginM wrapper. Notably, > >>> Simon's new TcFlatten.unflatten needs TcS... > >>> > >>> > >>> > >>> It think the only reason for this is that ‘unflatten’ needs to set > >>> evidence bindings, which in turn requires access to tcs_ev_binds. I > >>> think that everything else is in TcM. So I suppose you could carry > >>> around the EvBindsVar if you really didn’t want TcS. (And I can see why > >>> you wouldn’t; TcS has a lot of stuff you don’t need.) > >>> > >>> > >>> > >>> Simon > >>> > >>> > >>> > >>> > >>> > >>> *From:*Iavor Diatchki [mailto:iavor.diatc...@gmail.com] > >>> *Sent:* 10 November 2014 19:15 > >>> *To:* Adam Gundry > >>> *Cc:* ghc-devs@haskell.org; Simon Peyton Jones > >>> *Subject:* Re: Typechecker plugins: request for review and another > >>> workflow question > >>> > >>> > >>> > >>> Hi, > >>> > >>> > >>> > >>> On Mon, Nov 10, 2014 at 1:31 AM, Adam Gundry <a...@well-typed.com > >>> <mailto:a...@well-typed.com>> wrote: > >>> > >>> > >>> On the subject of that "nearly", I'm interested to learn whether you > >>> have a suggestion to deal with unflattening, because the interface > >>> still > >>> works with flat constraints only. Simon's changes should make it more > >>> practical to unflatten inside the plugin, but it would be far easier > >>> (at > >>> least for my purposes) if it was simply given unflattened constraints. > >>> I > >>> realise that this would require the plugin loop to be pushed further > >>> out, however, which has other difficulties. > >>> > >>> > >>> > >>> Not sure what to do about this. With the current setup, I think either > >>> way, the plugin would have to do some extract work. Perhaps we should > >>> run the plugins on the unflattened constraints, and leave to the plugins > >>> to manually temporarily "flatten" terms from external theories? For > >>> example, if the type-nat plugin saw `2 * F a ~ 4`, it could temporarily > >>> work with `2 * x ~ 4`, and then when it figures out that `x ~ 2`, it > >>> could emit `F a ~ 2` (non-canonical), which would go around again, and > >>> hopefully get fully simplified. > >>> > >>> > >>> > >>> > >>> > >>> > >>> A few other issues, of lesser importance: > >>> > >>> * I still think it would be better to provide an escape hatch to the > >>> TcS, not merely the TcM, alongside the nice TcPluginM wrapper. Notably, > >>> Simon's new TcFlatten.unflatten needs TcS... > >>> > >>> I don't mind that but, if I recall correctly, to do this without more > >>> recursive modules, we had to split `TCSMonad` in two parts, one with the > >>> types, and one with other stuff. Eric and I did this once, but we > >>> didn't commit it, because it seemed like an orthogonal change. > >>> > >>> > >>> > >>> > >>> > >>> * Is there a way for my plugin to "solve" a given constraint (e.g. to > >>> discard the uninformative "a * 1 ~ a")? > >>> > >>> Yes, you'd say something like: `TcPluginOK [(evidence, "a * 1 ~ a")] []` > >>> > >>> > >>> > >>> The first field of `TcPluginOK` are things that are solved, the second > >>> one is new work. > >>> > >>> > >>> > >>> * It is unfortunately easy to create infinite loops by writing plugins > >>> that emit wanteds but make no useful progress. Perhaps there should be > >>> a > >>> limit on the number of times round the loop (like SubGoalDepth but for > >>> all constraints)? > >>> > >>> > >>> > >>> Indeed, if a plugin keeps generating new work, we could go in a loop, so > >>> maybe a limit of some sort is useful. However, note that if the plugin > >>> generates things that are already in the inert set, GHC should notice > >>> this and filter them, so we won't keep going. > >>> > >>> > >>> > >>> > >>> > >>> * Perhaps runTcPlugin should skip invoking the plugin if there are no > >>> wanteds? > >>> > >>> > >>> > >>> Oh, there is an important detail here that needs documentation! GHC > >>> will call the plugin twice: once to improve the givens, and once to > >>> solve the wanteds. The way to distinguish the two is exactly by the > >>> presence of the wanteds. > >>> > >>> > >>> > >>> Why might you want to improve the givens? Suppose you had something > >>> like `x * 2 ~ 4` as a given: then you'd really want the plugin to > >>> generate another given: `x ~ 2`, as this is likely to help the rest of > >>> the constraint solving process. > >>> > >>> > >>> > >>> > >>> * The use of ctev_evar in runTcPlugin is partial, and fails with a > >>> nasty error if the plugin returns a non-wanted in the solved > >>> constraints > >>> list. Would it be worth catching this error and issuing a sensible > >>> message that chastises the plugin author appropriately? > >>> > >>> > >>> > >>> Aha, good idea. Bad plugin! :-) > >>> > >>> > >>> > >>> > >>> > >>> * Finally, I presume the comment on runTcPlugin that "The plugin is > >>> provided only with CTyEq and CFunEq constraints" is simply outdated and > >>> should be removed? > >>> > >>> Yep, thanks! > >>> > >>> > >>> > >>> Apologies for the deluge of questions - please take them as evidence of > >>> my eagerness to use this feature! > >>> > >>> > >>> > >>> Thanks for your feedback! Also, if you feel like doing some hacking > >>> please do so---I am quite busy at the moment so I don't have a ton of > >>> time to work on it, so any help you be most appreciated. I know Eric is > >>> also quite keen on helping out so we can just coordinate over e-mail. > >>> > >>> > >>> > >>> -Iavor > >> > >> > >> -- > >> Adam Gundry, Haskell Consultant > >> Well-Typed LLP, http://www.well-typed.com/ > > > > > > -- > Regards, > > Austin Seipp, Haskell Consultant > Well-Typed LLP, http://www.well-typed.com/ _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://www.haskell.org/mailman/listinfo/ghc-devs