[GHC] #11482: Turn -fdefer-typed-holes on by default

[GHC]

#11482: Turn -fdefer-typed-holes on by default
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        Reporter:  thomie            |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9497, #11481     |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by thomie):

 Another option would be to turn `-fdefer-typed-holes` on by default in
 GHCi only. I'm not sure about this though. I general I prefer GHCi and GHC
 to behave the same as much possible. Their difference with regard to the
 MonomorphismRestriction is annoying enough already.

 > Cabal / stack use -fno-defer-typed-holes by default.

 Do you mean `cabal init` would add `ghc-options: -fno-defer-typed-holes`
 to the `*.cabal` file it creates? Or the default `.cabal/config` would get
 that entry? Or Cabal would always pass it to ghc?

 One workflow is to add library dependencies to a `.cabal` file, and then
 run `cabal repl`, which starts ghci.

 I like the suggestion of emitting a shorter warning for holes.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11482#comment:5>
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