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<p class="MsoNormal">Grego, <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Yes I think that should auto-specialise.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Which version of GHC are you using? Do you have this patch?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="Code">commit ef0135934fe32da5b5bb730dbce74262e23e72e8<o:p></o:p></p>
<p class="Code">Author: Simon Peyton Jones <a href="mailto:simonpj@microsoft.com">
<span style="font-family:"Calibri",sans-serif">simonpj@microsoft.com</span></a><o:p></o:p></p>
<p class="Code">Date: Thu Apr 8 22:42:31 2021 +0100<o:p></o:p></p>
<p class="Code"><o:p> </o:p></p>
<p class="Code"> Make the specialiser handle polymorphic specialisation<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Here’s why I ask. The call <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$fMonadIO_$c>> = \ (@a) (@b) -> $dm>> @IO $fMonadIO @a @b<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal">indeed applies $dm>> to $fMonadIO, but it also applies it to a and b. In the version of GHC you have, maybe that stops the call from floating up to the definition site, and being used to specialise it.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Can you make a repro case without your plugin?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Simon<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal"><span style="font-size:8.0pt;mso-fareast-language:EN-GB">PS: I am leaving Microsoft at the end of November 2021, at which point
<a href="mailto:simonpj@microsoft.com"><span style="color:#0563C1">simonpj@microsoft.com</span></a> will cease to work. Use
<a href="mailto:simon.peytonjones@gmail.com"><span style="color:#0563C1">simon.peytonjones@gmail.com</span></a> instead. (For now, it just forwards to simonpj@microsoft.com.)<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<div style="border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt">
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<p class="MsoNormal"><b><span lang="EN-US" style="mso-fareast-language:EN-GB">From:</span></b><span lang="EN-US" style="mso-fareast-language:EN-GB"> Erdi, Gergo <Gergo.Erdi@sc.com>
<br>
<b>Sent:</b> 06 October 2021 03:07<br>
<b>To:</b> Simon Peyton Jones <simonpj@microsoft.com><br>
<b>Cc:</b> Montelatici, Raphael Laurent <Raphael.Montelatici@sc.com>; GHC <ghc-devs@haskell.org><br>
<b>Subject:</b> Specialisation doesn't kick in (RE: Instantiation of overloaded definition *in Core*)<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p style="margin:15.0pt"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#317100">PUBLIC<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<div>
<p class="msipheader7557e74b" style="margin:0cm"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#317100">PUBLIC</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Thanks! Originally I was going to reply to this saying that my transformation isn’t running in CoreM so where do I get that environment from, but then I realized I can just build
it from the md_insts field of ModDetails. However, after thinking more about it, I also realized that I shouldn’t ever really need to conjure up dictionaries from thin air: the whole reason I am making a specific specialization of an overloaded function is
because I found somewhere a call at that type. But then, that call also gives me the dictionary!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Of course at this point, this sounds exactly like what GHC already does in `specProgram`. So maybe I should be able to just use that?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Unfortunately, my initial testing seems to show that even if I run `specBind` manually on my whole-program collected CoreProgram, it doesn’t do the work I would expect from it!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">In the following example, I have only kept the definitions that are relevant. Before specialisation, I have the following whole-program Core:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">(>>=)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> :: forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId[ClassOp], Arity=1, Caf=NoCafRefs, Str=<S(LSL),U(A,U,A)>]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">(>>=)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> = \ (@(m :: * -> *)) (v_sGm [Occ=Once1!] :: Monad m) -><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> case v_sGm of<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> { C:Monad _ [Occ=Dead] v_sGp [Occ=Once1] _ [Occ=Dead] -><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> v_sGp<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> }<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$dm>> :: forall (m :: * -> *) a b. Monad m => m a -> m b -> m b<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId, Arity=3, Unf=OtherCon []]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$dm>><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> = \ (@(m :: * -> *))<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> ($dMonad [Occ=Once1] :: Monad m)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (@a)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (@b)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (ma [Occ=Once1] :: m a)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (mb [Occ=OnceL1] :: m b) -><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> let {<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> sat_sGQ [Occ=Once1] :: a -> m b<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> [LclId]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> sat_sGQ = \ _ [Occ=Dead] -> mb } in<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> >>= @m $dMonad @a @b ma sat_sGQ<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">C:Monad [InlPrag=NOUSERINLINE CONLIKE]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> :: forall (m :: * -> *).<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> Applicative m<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> -> (forall a b. m a -> (a -> m b) -> m b)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> -> (forall a b. m a -> m b -> m b)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> -> Monad m<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId[DataCon], Arity=3, Caf=NoCafRefs, Cpr=m1, Unf=OtherCon []]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">C:Monad<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> = \ (@(m :: * -> *))<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (eta_B0 [Occ=Once1] :: Applicative m)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (eta_B1 [Occ=Once1] :: forall a b. m a -> (a -> m b) -> m b)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (eta_B2 [Occ=Once1] :: forall a b. m a -> m b -> m b) -><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> C:Monad @m eta_B0 eta_B1 eta_B2<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$fMonadIO [InlPrag=NOUSERINLINE CONLIKE] :: Monad IO<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId[DFunId]]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$fMonadIO = C:Monad @IO $fApplicativeIO bindIO $fMonadIO_$c>>;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$fMonadIO_$c>> [Occ=LoopBreaker]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> :: forall a b. IO a -> IO b -> IO b<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$fMonadIO_$c>> = \ (@a) (@b) -> $dm>> @IO $fMonadIO @a @b;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">sat_sHr :: IO ()<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[LclId]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">sat_sHr = returnIO @() ()<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">sat_sHq :: IO ()<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[LclId]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">sat_sHq = returnIO @() ()<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">main :: IO ()<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">main = $fMonadIO_$c>> @() @() sat_sHq sat_sHr<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Now I pass this to GHC’s `specBind`, but the output is exactly the same as the input! (or it’s close enough that I can’t spot the difference).
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">(>>=)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> :: forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId[ClassOp], Arity=1, Caf=NoCafRefs, Str=<S(LSL),U(A,U,A)>]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">(>>=)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> = \ (@(m :: * -> *)) (v_sGm [Occ=Once1!] :: Monad m) -><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> case v_sGm of<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> { C:Monad _ [Occ=Dead] v_sGp [Occ=Once1] _ [Occ=Dead] -><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> v_sGp<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> }<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$dm>> :: forall (m :: * -> *) a b. Monad m => m a -> m b -> m b<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId, Arity=3, Unf=OtherCon []]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$dm>><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> = \ (@(m :: * -> *))<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> ($dMonad [Occ=Once1] :: Monad m)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (@a)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (@b)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (ma [Occ=Once1] :: m a)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (mb [Occ=OnceL1] :: m b) -><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> let {<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> sat_MHt [Occ=Once1] :: a -> m b<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> [LclId]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> sat_MHt = \ _ [Occ=Dead] -> mb } in<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> >>= @m $dMonad @a @b ma sat_MHt<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">C:Monad [InlPrag=NOUSERINLINE CONLIKE]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> :: forall (m :: * -> *).<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> Applicative m<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> -> (forall a b. m a -> (a -> m b) -> m b)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> -> (forall a b. m a -> m b -> m b)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> -> Monad m<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId[DataCon], Arity=3, Caf=NoCafRefs, Cpr=m1, Unf=OtherCon []]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">C:Monad<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> = \ (@(m :: * -> *))<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (eta_B0 [Occ=Once1] :: Applicative m)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (eta_B1 [Occ=Once1] :: forall a b. m a -> (a -> m b) -> m b)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> (eta_B2 [Occ=Once1] :: forall a b. m a -> m b -> m b) -><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> C:Monad @m eta_B0 eta_B1 eta_B2<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$fMonadIO [InlPrag=NOUSERINLINE CONLIKE] :: Monad IO<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId[DFunId]]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$fMonadIO = C:Monad @IO $fApplicativeIO bindIO $fMonadIO_$c>>;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$fMonadIO_$c>> [Occ=LoopBreaker]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB"> :: forall a b. IO a -> IO b -> IO b<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">$fMonadIO_$c>> = \ (@a) (@b) -> $dm>> @IO $fMonadIO @a @b;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">sat_sHr :: IO ()<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[LclId]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">sat_sHr = returnIO @() ()<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">sat_sHq :: IO ()<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[LclId]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">sat_sHq = returnIO @() ()<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">main :: IO ()<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">[GblId]<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-family:"Lucida Console";mso-fareast-language:EN-GB">main = $fMonadIO_$c>> @() @() sat_sHq sat_sHr<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Why is that? I would have expected that the call chain main >-> $fMonadIO_$c>> >-> $dm>> would have resulted in a specialization along the lines of:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">$dm>>_IO :: forall a b. IO a -> IO b -> IO b<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">>>=_IO :: forall a b. IO a -> (a -> IO b) -> IO b<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">With appropriate definitions that can then be simplified away.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">But none of this seems to happen -- $dm>> doesn’t get an IO-specific version, and so $fMonadIO_$c>> still ends up with a dictionary-passing call to $dm>>. Isn’t this exactly
the situation that the specialiser is supposed to eliminate?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"> Gergo<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="mso-fareast-language:EN-GB">From:</span></b><span lang="EN-US" style="mso-fareast-language:EN-GB"> Simon Peyton Jones <<a href="mailto:simonpj@microsoft.com">simonpj@microsoft.com</a>>
<br>
<b>Sent:</b> Monday, October 4, 2021 7:29 PM<br>
<b>To:</b> Erdi, Gergo <<a href="mailto:Gergo.Erdi@sc.com">Gergo.Erdi@sc.com</a>><br>
<b>Cc:</b> Montelatici, Raphael Laurent <<a href="mailto:Raphael.Montelatici@sc.com">Raphael.Montelatici@sc.com</a>>; GHC <<a href="mailto:ghc-devs@haskell.org">ghc-devs@haskell.org</a>><br>
<b>Subject:</b> [External] RE: Instantiation of overloaded definition *in Core*<o:p></o:p></span></p>
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</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p style="margin:15.0pt"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#317100">PUBLIC<o:p></o:p></span></p>
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<p class="MsoNormal">You can look it up in the class instance environment, which the Simplifier does have access to it. That’s relatively easy when you have a simple dictionary like (Monad IO). But if you want (Eq [Int]) you first of all have to look up the
(Eq [a]) dictionary, then the Eq Int dictionary, and apply the former to the latter. We don’t (yet) have a simple API to do that, although it would not be hard to create one.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Simon<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal"><span style="font-size:8.0pt;mso-fareast-language:EN-GB">PS: I am leaving Microsoft at the end of November 2021, at which point
<a href="mailto:simonpj@microsoft.com"><span style="color:#0563C1">simonpj@microsoft.com</span></a> will cease to work. Use
<a href="mailto:simon.peytonjones@gmail.com"><span style="color:#0563C1">simon.peytonjones@gmail.com</span></a> instead. (For now, it just forwards to
<a href="mailto:simonpj@microsoft.com">simonpj@microsoft.com</a>.)<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="mso-fareast-language:EN-GB">From:</span></b><span lang="EN-US" style="mso-fareast-language:EN-GB"> ghc-devs <<a href="mailto:ghc-devs-bounces@haskell.org">ghc-devs-bounces@haskell.org</a>>
<b>On Behalf Of </b>Erdi, Gergo via ghc-devs<br>
<b>Sent:</b> 04 October 2021 10:30<br>
<b>To:</b> 'GHC' <<a href="mailto:ghc-devs@haskell.org">ghc-devs@haskell.org</a>><br>
<b>Cc:</b> Montelatici, Raphael Laurent <<a href="mailto:Raphael.Montelatici@sc.com">Raphael.Montelatici@sc.com</a>><br>
<b>Subject:</b> Instantiation of overloaded definition *in Core*<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="msipheader7557e74b" style="margin:0cm"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#317100">PUBLIC</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">I’d like to instantiate Core definitions. For example, suppose I have the following Core definition:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:Consolas">foo :: forall m a b. Monad m => m a -> m b -> m b<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:Consolas">foo = \ @m ($d :: Monad m) @a @b (ma :: m a) (mb :: m b) -> ...<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Now let’s say I’d like to instantiate it for m ~ IO. It is quite straightforward to go from the above to:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:Consolas">foo_IO_0 :: forall a b. Monad IO => IO a -> IO b -> IO b<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:Consolas">foo_IO_0 = \ ($d :: Monad IO) @a @b (ma :: IO a) (mb :: IO b) -> ...<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">However, I would like to go all the way to:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:Consolas">foo_IO :: forall a b. IO a -> IO b -> IO b<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:Consolas">foo_IO = \ @a @b (ma :: IO a) (mb :: IO b) -> ...<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Because instances are coherent, it should be sound to replace all occurrences of
</span><span style="font-size:10.0pt;font-family:Consolas">$d</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif"> with “the” dictionary for
</span><span style="font-size:10.0pt;font-family:Consolas">Monad IO</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif">. However, the places I’ve found for this kind of query seem to live in the typechecker. How do I access this information
while working with Core?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif"> Gergo<o:p></o:p></span></p>
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