Yep, that seems to work. I'll add a note explaining why we need unfoldings here. On Nov 11, 2014 10:14 PM, "Simon Peyton Jones" <simo...@microsoft.com> wrote:
> Oh bother, that is _so_ tiresome. The desugarer establishes the let/app > invariant, so we get > > I# x_help > > but if x_help has a compulsory unfolding to (x void), returning an Int#, > that violates the let/app invariant. Sigh. This is a ridiculous amount of > work for a tiny corner (pattern synonyms for unboxed constants). > > Harump. Let's see. We are talking only of things like this > > pattern P = 4# > > correct? Perhaps it may be simpler to make the psWrapper in PatSyn be > psWrapper :: Either Id Literal > and treat such patterns specially from the moment we first see them? That > would eliminate all this void stuff entirely. > > Pursuing the current line, though, I suppose that the desugarer could > inline compulsory unfoldings during desugaring itself. In this line, add a > case for when var has a compulsory unfolding. > > dsExpr (HsVar var) = return (varToCoreExpr var) -- See Note > [Desugaring vars] > > That would, I suppose, be the quickest pathc. > > Simon > > | -----Original Message----- > | From: ghc-devs [mailto:ghc-devs-boun...@haskell.org] On Behalf Of Dr. > | ERDI Gergo > | Sent: 08 November 2014 14:03 > | To: GHC Devs > | Subject: let/app invariant violated by code generated with mkCoreApp > | > | Hi, > | > | I'm trying to attach (f Void#) as a compulsory unfolding to an Id. > | Here's what I tried originally: > | > | let unfolding = mkCoreApp (Var worker_id) (Var voidPrimId) > | wrapper_id' = setIdUnfolding wrapper_id $ > | mkCompulsoryUnfolding unfolding > | > | However, when I try to use wrapper_id' in the desugarer, the Core > | linter looks at me strange. This is the original Core: > | > | f :: Int > | [LclIdX, Str=DmdType] > | f = break<1>() GHC.Types.I# Main.$WPAT > | > | and this is the error message ($WPAT is the wrapper_id', PAT is the > | worker_id in this example) > | > | <no location info>: Warning: > | In the expression: I# (PAT void#) > | This argument does not satisfy the let/app invariant: PAT void# > | > | Now, I thought I'd make sure mkCoreApp generated correct Core by > | writing it out by hand: > | > | let unfolding = Case (Var voidPrimId) voidArgId pat_ty > | [(DEFAULT,[],App (Var worker_id) (Var voidArgId))] > | > | however, bizarrely, this *still* results in *the same* error message, > | as if something was transforming it back to a straight App. > | > | Anyone have any hints what I'm doing wrong here? > | > | Bye, > | Gergo > | > | -- > | > | .--= ULLA! =-----------------. > | \ http://gergo.erdi.hu \ > | `---= ge...@erdi.hu =-------' > | You are in a twisty maze of little install diskettes. > | _______________________________________________ > | ghc-devs mailing list > | ghc-devs@haskell.org > | http://www.haskell.org/mailman/listinfo/ghc-devs >
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