RE: Re: Shadowing in toIface* output

PUBLIC OK, I must be doing something wrong then. I am now looking at Tidy (not Prep) output, and I see Core like this: showsPrec :: forall a. Show a => Int -> a -> ShowS [GblId[ClassOp], Arity=1, Caf=NoCafRefs, Str=, RULES: Built in rule for showsPrec: "Class op showsPrec"] showsPrec = \ (@a_a1G3) (v_B1 :: Show a_a1G3) -> case v_B1 of v_B1 { C:Show v_B2 v_B3 v_B4 -> v_B2 } so if I'm reading this right, these vs are still shadowing. I am using tidyProgram on the output of hscSimplify, and then taking the cg_binds of its result. What else should I do to get tidy (heh) Tidy output? From: ghc-devs On Behalf Of Simon Peyton Jones Sent: Monday, April 4, 2022 4:28 PM To: Gergő Érdi Cc: GHC Devs Subject: [External] Re: Shadowing in toIface* output ATTENTION: This email came from an external source. Do not open attachments or click on links from unknown senders or unexpected emails. Always report suspicious emails using the Report As Phishing button in Outlook to protect the Bank and our clients. So does that mean Tidy produces unique `occNameFS`s, and then `Prep` breaks them? Tidy does not produce unique OccNames. Rather, it avoids shadowing, so that if you delete all the uniques and print out the program (which is precisely what happens in an .hi file) you'll still get something sensible. I'm not sure whether or not Prep maintains this invariant. There is no particular reason it should. It might, but it is not (currently) a goal. Simon On Sat, 2 Apr 2022 at 04:35, Gergő Érdi mailto:gergo@erdi.hu> wrote: So does that mean Tidy produces unique `occNameFS`s, and then `Prep` breaks them? On Fri, Apr 1, 2022 at 10:35 PM Josh Meredith mailto:joshmeredith2008@gmail.com> wrote:

Hi,

I encountered this when we used that for Plutus. I'll have to dig up the details, but IIRC `toIfaceExpr` expects GHC to have already tidied the output, which deals with this issue of overlapping variable names.

Cheers, Josh

On Sat, 2 Apr 2022 at 01:26, ÉRDI Gergő mailto:gergo@erdi.hu> wrote:

...

Hi,

I'm trying to save (Prep'd) Core bindings right next to the serialized `ModIface` (so basically `put_`ing them into the same bytestream, after the `ModIface`), and that's exactly what the functions in `GHC.CoreToIface` seem to be for, so I expected it to Just Work. However, I noticed that I very frequently get problems with shadowing. For example, Core that looks like `\v{u1} v{u2} -> v{u1}` would get translated to `\v v -> v`, which is disastrous since these locally bound `Var`s are represented as just their `getOccFS` (i.e. the `FastString` `"v"`).

But this can't be right: if `toIfaceExpr` &c. would fail this blatently, then the unfoldings couldn't be saved & restored, which is something GHC itself does as part of normal `.hi` file handling. So clearly I must be doing something wrong.

So I guess my question could be, what could be causing `toIfaceExpr` (a pure function!) to behave this way for my Cores? But then, if I look at the implementation of `toIface*`, I can see that it really doesn't do anything smarter than just storing `getOccFS` in the interface (no uniques in sight)-- so maybe my *real* question is, what is GHC itself doing so that it doesn't have this same problem?

Thanks, Gergo _______________________________________________ ghc-devs mailing list ghc-devs@haskell.orgmailto:ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devshttps://clicktime.symantec.com/3BestP7qr2g6Y7xBfCxdDwr6xU?u=http%3A%2F%2Fmai...

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