[GHC] #14203: GHC-inferred type signature doesn't actually typecheck

[GHC]

#14203: GHC-inferred type signature doesn't actually typecheck
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.1
  checker)                           |             Keywords:  TypeInType,
      Resolution:                    |  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 Replying to [comment:9 simonpj]:
 > I don't agree.  It's the definition of `Foo` that has an ambiguous kind.

 OK, sure. The point is—there's //some// definition in this program with an
 ambiguous kind, and `AllowAmbiguousTypes` is not convincing GHC to accept
 it. If the burden of ambiguity proof needs to be shifted to `Foo` instead,
 that's fine.

 > What is "this"?  Rejecting the definition of `Foo` (which would be the
 effect of checking `Foo`'s kind for ambiguity) would not typecheck more
 programs!

 The point is that I //want// GHC to accept `Foo` (and `bar`). The
 mechanism by which I normally do so (`AllowAmbiguousTypes`) is failing me
 here.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14203#comment:10>
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