[GHC] #14370: non-deferred typed hole despite -fdefer-typed-holes

[GHC]

#14370: non-deferred typed hole despite -fdefer-typed-holes
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        Reporter:  int-e             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  error/warning at compile-time      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by int-e):

 Replying to [comment:1 monoidal]:
 > Does
 [https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html
 #deferred-type-errors-in-ghci this] answer your question?

 Yes and no. I still believe that the behavior is surprising, but this
 means it's a feature, not a bug (I don't care enough to argue otherwise).
 Btw, from this section I would conclude that `length [r]` should also
 produce an error, since both typed holes and out of scope variables fall
 under the headline
 [https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html
 #deferring-type-errors-to-runtime Deferring type errors to runtime].

 In any case it appears that the documentation can be improved a bit.

  * clarify in
 [https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html
 #deferred-type-errors-in-ghci Deferred type errors in GHCi] that this
 applies to type checking errors (including typed holes) but not to name
 resolution (out of scope variables)
  * I didn't find the GHCi exception when reading
 [https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html
 #typed-holes Typed Holes] so a forward reference may be helpful
  * The description of
 [https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/using-
 warnings.html#ghc-flag--fdefer-type-errors -fdefer-type-errors] should
 mention that it implies -fdefer-out-of-scope-variables

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14370#comment:2>
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