Re: -ddump-types vs -fprint-explicit-foralls, and symbol-ness of worker/wrapper names [Re: [commit: ghc] master: Pretty-print the following TyThings via their IfaceDecl counterpart: * AnId * ACoAxiom * AConLike (065c35a) (fwd)]

Sounds good to me. On Mon, Mar 17, 2014 at 3:23 PM, Dr. ÉRDI Gergő wrote:

Exactly, the problem is precisely that $foo is regarded as an infix operator in that code path, so with my change, it would be classified as prefix. On Mar 17, 2014 10:10 PM, "Simon Peyton Jones" wrote:

...

Do they show up in –ddump-simpl? It would be nice to keep that output as readable as possible, as there are quite a few of us that read it on a regular basis.

I don’t think so (because –ddump-simpl doesn’t print **any** operators in parens) but I could be wrong, and I agree that would be bad.

Does that mean that any operator that starts with $ will now not be considered infix for printing purposes?

No, I believe that Gergo’s suggestion is that a function be considered infix operator (for display purposes) only if all its characters are operator chars, rather than just the first one.

Simon

*From:* Johan Tibell [mailto:johan.tibell@gmail.com] *Sent:* 17 March 2014 14:00 *To:* Simon Peyton Jones *Cc:* Dr. ERDI Gergo; GHC Devs *Subject:* Re: -ddump-types vs -fprint-explicit-foralls, and symbol-ness of worker/wrapper names [Re: [commit: ghc] master: Pretty-print the following TyThings via their IfaceDecl counterpart: * AnId * ACoAxiom * AConLike (065c35a) (fwd)]

On Mon, Mar 17, 2014 at 2:45 PM, Simon Peyton Jones < simonpj@microsoft.com> wrote:

| The one interesting case is T4306 which fails because the generated name

| $wupd is regarded as an infix name, and thus with my new code is | rendered as | | ($wupd) :: GHC.Prim.Double# -> GHC.Prim.Double# | | instead of the old | | $wupd :: GHC.Prim.Double# -> GHC.Prim.Double#

I think it'd also be ok just to accept this output too. These "$wxx" names are generated by GHC and won't show up in user output. It doesn't much matter displaying them in parens.

Do they show up in -ddump-simpl? It would be nice to keep that output as readable as possible, as there are quite a few of us that read it on a regular basis.

But changing isLexVarSym is probably equally fine too. I think (worth a check) that it's only called for display purposes, and not in any performance-critical parts.

Whichever you choose, add a Note with isLexVarSym to explain the issue and the choice.

Does that mean that any operator that starts with $ will now not be considered infix for printing purposes?

-- Johan