#9139 closed bug (duplicate)

Using lift with StateT and Maybe on GHCI

Reported by: Jefffrey Owned by:
Priority: low Milestone:
Component: GHCi Version: 7.6.3
Keywords: Cc: hvr
Operating System: MacOS X Architecture: Unknown/Multiple
Type of failure: Other Test Case:
Blocked By: Blocking:
Related Tickets: Differential Revisions:

Description

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. :)

Change History (1)

comment:1 Changed 10 months ago by simonpj

  • Resolution set to duplicate
  • Status changed from new to closed

I suspect this is #7368. Anyway it works fine in 7.8 I think.

Do reopen if I'm wrong.

Simon

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