[GHC] #13446: Deferred type error sneaks in with -fno-defer-type-errors enabled

[GHC]

#13446: Deferred type error sneaks in with -fno-defer-type-errors enabled
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.2
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC accepts       |  Unknown/Multiple
  invalid program                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by RyanGlScott):

 * cc: simonpj (added)


Comment:

 Commit 03541cbae50f0d1cdf99120ab88698f29a278159

 {{{
 From 03541cbae50f0d1cdf99120ab88698f29a278159 Mon Sep 17 00:00:00 2001
 From: Simon Peyton Jones <simonpj at microsoft.com>
 Date: Fri, 9 Sep 2016 17:42:42 +0100
 Subject: [PATCH] Be less picky about reporing inaccessible code

 Triggered by the discussion on Trac #12466, this patch
 makes GHC less aggressive about reporting an error when
 there are insoluble Givens.

 Being so agressive was making some libraries fail to
 compile, and is arguably wrong in at least some cases.
 See the discussion on the ticket.

 Several test now pass when they failed before; see
 the files-modified list for this patch.
 }}}

 caused this regression. Thought, Simon?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13446#comment:1>
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