[GHC] #10569: Optionally treat an out-of-scope variable like a typed hole

[GHC]

#10569: Optionally treat an out-of-scope variable like a typed hole
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        Reporter:  simonpj           |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 To me, the problem here is that we've conflated two goals:
 1. Adding type information to out-of-scope variables.
 2. Allowing deferment of out-of-scope variables.

 I think (1) is a clear win (modulo #12092). But I tend to think (2) isn't.
 Even if someone is deferring type errors, I imagine most people don't want
 to defer scope errors. I personally favor adding the flag. (Important
 motivation: thinking about teaching Haskell and seeing if `-fdefer-type-
 errors` can help.)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10569#comment:10>
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