[GHC] #14149: Tyepchecker generates top-level unboxed coercion

[GHC]

#14149: Tyepchecker generates top-level unboxed coercion
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        Reporter:  simonpj           |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
                                     |  testsuite/tests/typecheck/should_compile/T14149
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"08003e7f4abafb0c9fe084e4670122ce67cf45dd/ghc"
 08003e7f/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="08003e7f4abafb0c9fe084e4670122ce67cf45dd"
 Make out-of-scope errors more prominent

 Generally, when the type checker reports an error, more serious
 ones suppress less serious ones.

 A "variable out of scope" error is arguably the most serious of all,
 so this patch moves it to the front of the list instead of the end.

 This patch also fixes Trac #14149, which had
 -fdefer-out-of-scope-variables, but also had a solid type error.
 As things stood, the type error was not reported at all, and
 compilation "succeeded" with error code 0.  Yikes.

 Note that

 - "Hole errors" (including out of scope) are never suppressed.
   (maybeReportHoleError vs maybeReportError in TcErorrs)
   They can just get drowned by the noise.

 - But with the new orientation, out of scope errors will suppress
   type errors.  That would be easy to change.
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14149#comment:5>
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