#2268: ghci "*** Exception: expectJust upseep1"
-------------------------------+--------------------------------------------
Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Component: GHCi
Version: 6.8.2 | Severity: normal
Keywords: | Testcase:
Architecture: x86_64 (amd64) | Os: Linux
-------------------------------+--------------------------------------------
ghci gets confused, reporting "*** Exception: expectJust upseep1". I think
it's related to having pre-compiled source files that cyclicly import each
other, but havn't double checked/proven it.
Trace to reproduce the bug here: (notice that at the start Simplify.hs has
a bug in it, and after loading it, but before doing :!cat Simplify.hs I
have fixed the error in Simplify.hs)
{{{
16:56:38 - [EMAIL PROTECTED]:/tmp/GhcBug.hs
>ls
Bookmarks.hs Bookmarks.hs-boot Cursor.hs Simplify.hs
16:56:51 - [EMAIL PROTECTED]:/tmp/GhcBug.hs
>ghc --make -c Cursor.hs Bookmarks.hs
[1 of 3] Compiling Bookmarks[boot] ( Bookmarks.hs-boot, Bookmarks.o-boot
)
[2 of 3] Compiling Cursor ( Cursor.hs, Cursor.o )
[3 of 3] Compiling Bookmarks ( Bookmarks.hs, Bookmarks.o )
16:57:05 - [EMAIL PROTECTED]:/tmp/GhcBug.hs
>cat Simplify.hs
module HExp.Simplify where
import Cursor(Cursor)
iterateMaybe :: (a -> Maybe a) -> a -> [a]
iterateMaybe f init = init : maybe [] (iterateMaybe) (f init)
16:57:20 - [EMAIL PROTECTED]:/tmp/GhcBug.hs
>ghci Simplify.hs
GHCi, version 6.8.2: http://www.haskell.org/ghc/ :? for help
Loading package base ... linking ... done.
[3 of 4] Compiling HExp.Simplify ( Simplify.hs, interpreted )
Simplify.hs:6:39:
Couldn't match expected type `[a]'
against inferred type `a1 -> [a1]'
Probable cause: `iterateMaybe' is applied to too few arguments
In the second argument of `maybe', namely `(iterateMaybe)'
In the second argument of `(:)', namely
`maybe [] (iterateMaybe) (f init)'
Failed, modules loaded: Cursor, Bookmarks, Bookmarks.
Prelude Bookmarks> :!cat Simplify.hs
module HExp.Simplify where
import Cursor(Cursor)
iterateMaybe :: (a -> Maybe a) -> a -> [a]
iterateMaybe f init = init : maybe [] (iterateMaybe f) (f init)
Prelude Bookmarks> :r
*** Exception: expectJust upseep1
> Leaving GHCi.
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2268>
GHC <http://www.haskell.org/ghc/>
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