D1182: Implement improved error messages for ambiguous type variables (#10733)

[Edward Z. Yang]

Thanks Thomas, I think this workaround is fine.

Excerpts from Thomas Miedema's message of 2015-09-03 09:17:35 -0700:
> The bug is trigger by Maybe now being a wired-in type. See
> https://phabricator.haskell.org/D1208 for a workaround.
> 
> On Thu, Sep 3, 2015 at 6:13 PM, Edward Z. Yang <ezyang at mit.edu> wrote:
> 
> > It's certainly true that hsig is in flux, but it doesn't seem like
> > injective type families should have broken this test.  I'll take a look.
> >
> > Edward
> >
> > Excerpts from Simon Peyton Jones's message of 2015-09-03 09:08:23 -0700:
> > > Edward
> > >
> > > | Jan's injective type families commit is causing tcfail220 to fail, but
> > > | that's unrelated to this ticket.
> > >
> > > This is true.  I told Jan to commit anyway because tcfail220 is a "hsig"
> > test, and
> > >  a) I know that hsigs are in flux (although I am not clear about how)
> > >  b) I don't understand them enough to fix.
> > >
> > > So I hope it's ok to have broken this.  Jan and I can certainly help
> > when you want to fix it.
> > >
> > > Meanwhile would you mark it as expect-broken.  (Although I am not sure
> > that it's worth opening a fresh ticket for it.)
> > >
> > > thanks
> > >
> > > Simon
> > >
> > > | -----Original Message-----
> > > | From: noreply at phabricator.haskell.org
> > > | [mailto:noreply at phabricator.haskell.org]
> > > | Sent: 03 September 2015 07:11
> > > | To: Simon Peyton Jones
> > > | Subject: [Differential] [Commented On] D1182: Implement improved error
> > > | messages for ambiguous type variables (#10733)
> > > |
> > > | KaneTW added a comment.
> > > |
> > > | Jan's injective type families commit is causing tcfail220 to fail, but
> > > | that's unrelated to this ticket.
> > > |
> > > |
> > > | REPOSITORY
> > > |   rGHC Glasgow Haskell Compiler
> > > |
> > > | REVISION DETAIL
> > > |   https://phabricator.haskell.org/D1182
> > > |
> > > | EMAIL PREFERENCES
> > > |   https://phabricator.haskell.org/settings/panel/emailpreferences/
> > > |
> > > | To: KaneTW, simonpj, bgamari, austin
> > > | Cc: goldfire, simonpj, thomie
> > --- End forwarded message ---
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