[GHC] #10623: Handling of ASCII encodings introduced in D898 breaks Unicode terminal detection

[GHC]

#10623: Handling of ASCII encodings introduced in D898 breaks Unicode terminal
detection
-------------------------------------+-------------------------------------
              Reporter:  bgamari     |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.2-rc2
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |        Blocked By:
             Test Case:  T8958a      |   Related Tickets:  #10298, #7695
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
 Phab:D898 was primarily intended to fix hangs in the event that `iconv`
 was unavailable (namely #10298 and #7695). In addition to this fix, it
 also introduced self-contained handling of ANSI terminals to allow
 compiled executables to run in minimal environments lacking iconv.

 However, the behavior that the patch introduced is highly suspicious.
 Specifically, it gives the user a UTF-8 encoding even if they requested
 ASCII.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10623>
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