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:[email protected]]
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 
<[email protected]<mailto:[email protected]>> 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

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