[GHC] #14963: ghci -fdefer-type-errors can't run IO action from another module

[GHC]

#14963: ghci -fdefer-type-errors can't run IO action from another module
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        Reporter:  elaforge          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.4.2
       Component:  GHCi              |              Version:  8.4.1
      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 elaforge):

 This is just a peanut-gallery comment, so forgive the naivety, but my
 impression is that Idris treats `do` desugaring purely syntactically, so
 e.g. you don't even need a Monad class or the expected types, just
 something called (>>=) and pure in scope.  Idris of course does a lot of
 things fundamentally differently, not the least of which is type-directed
 name overloading, but that seems orthogonal.  What's the problem with
 treating `do` as a syntax macro before even getting to typechecking?

 I gather the problem above is all rebindable syntax not just `do` and
 (>>=), but it made me curious about that one thing.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14963#comment:12>
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