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-bounces@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 \ | `---= gergo@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