[GHC] #9139: Using lift with StateT and Maybe on GHCI
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Fri May 23 12:56:54 UTC 2014
#9139: Using lift with StateT and Maybe on GHCI
------------------------------------+----------------------------
Reporter: Jefffrey | Owner:
Type: bug | Status: new
Priority: low | Milestone:
Component: GHCi | Version: 7.6.3
Keywords: | Operating System: MacOS X
Architecture: Unknown/Multiple | Type of failure: Other
Difficulty: Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: |
------------------------------------+----------------------------
I was playing around with `StateT` and `Maybe` today and I run the
following two commands (consider that `TC` == `import qualified
Control.Monad.Trans.Class as TC`:
{{{
ghci> let g = TC.lift Just [3, 4] :: StateT [Int] Maybe Int
}}}
which led to a:
{{{
<interactive>:54:9:
Couldn't match kind `* -> *' with `*'
Expected type: [t0] -> StateT [Int] Maybe Int
Actual type: [t0] -> StateT [Int] Maybe Int
Kind incompatibility when matching types:
[t_i] :: * -> *
[t0] :: *
The function `TC.lift'ghc: panic! (the 'impossible' happened)
(GHC version 7.6.3 for x86_64-apple-darwin):
kindFunResult
<<details unavailable>>
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
}}}
and
{{{
> let g = TC.lift Just (1, [3, 4]) :: StateT [Int] Maybe Int
}}}
which led to:
{{{
<interactive>:55:9:
Couldn't match kind `* -> *' with `*'
Expected type: (t0, [t1]) -> StateT [Int] Maybe Int
Actual type: (t0, [t1]) -> StateT [Int] Maybe Int
Kind incompatibility when matching types:
(t_i, [t_l]) :: * -> *
(t0, [t1]) :: *
The function `TC.lift'ghc: panic! (the 'impossible' happened)
(GHC version 7.6.3 for x86_64-apple-darwin):
kindFunResult
<<details unavailable>>
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
}}}
I'm just doing what the last line asked me. :)
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9139>
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