[GHC] #14332: Deriving clauses can have forall types
GHC
ghc-devs at haskell.org
Tue Oct 17 22:22:55 UTC 2017
#14332: Deriving clauses can have forall types
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Reporter: RyanGlScott | Owner: (none)
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type | Version: 8.2.1
checker) |
Resolution: | Keywords: deriving
Operating System: Unknown/Multiple | Architecture:
Type of failure: GHC accepts | Unknown/Multiple
invalid program | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
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Comment (by RyanGlScott):
Replying to [comment:16 simonpj]:
> In comment:14 I say that GHC is behaving right.
Except that it's clearly not, as evidenced in comment:7. I don't see a way
to fix that short of overhauling how `deriving` clauses are
renamed/typechecked, which I don't feel like I'd be able to accomplish
without some mentoring.
> You seem to think I'm asking for something subtle in the
implementationn, but I'm not.
I firmly disagree hereāthe way GHC typechecks `deriving` clauses is ripe
with subtlety! It's caused me endless amounts of headaches trying to fix
bugs like #10524 and #10561 in the past, as just two data points.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14332#comment:17>
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