#1865: GHCi debugger crashes with :print
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Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: GHCi | Version: 6.9
Severity: normal | Keywords:
Testcase: | Architecture: Unknown
Os: Unknown |
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To reproduce:
1. Enter the following code into a source file:
{{{
{-# LANGUAGE NoMonomorphismRestriction #-}
d (i, j) = i + j
dmerge xs [] = xs
dmerge [] ys = ys
dmerge (x:xs) (y:ys) | d x < d y = x : dmerge xs (y:ys)
| d x == d y = x : dmerge xs ys
| otherwise = y : dmerge (x:xs) ys
pairs xs = head xs : pairs (tail xs `dmerge` map (\(i,j) -> (i+1,j+1)) xs
`dmerge` map (\(i,j) -> (i, j+1)) xs)
allpairs = pairs [(1,2)]
}}}
2. Start ghci, and pass this file as a parameter.
3. Type `:print allpairs`
GHCi will crash.
{{{
[EMAIL PROTECTED]:~/haskell/projects/euler$ ghci -ignore-dot-ghci
BugTest.hs
GHCi, version 6.9.20071101: http://www.haskell.org/ghc/ :? for help
Loading package base ... linking ... done.
[1 of 1] Compiling Main ( BugTest.hs, interpreted )
Ok, modules loaded: Main.
*Main> :print allpairs
*** Exception: ghci/Debugger.hs:84:11-72: Irrefutable pattern failed for
pattern Data.Maybe.Just subst
ghc-6.9.20071101: panic! (the 'impossible' happened)
(GHC version 6.9.20071101 for i386-unknown-linux):
ghci/Debugger.hs:84:11-72: Irrefutable pattern failed for pattern
Data.Maybe.Just subst
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
}}}
Note that it does not crash without the LANGUAGE directive, so this
appears to have something to do with the polymorphic type.
{{{
[EMAIL PROTECTED]:~/haskell/projects/euler$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.9.20071101
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1865>
GHC <http://www.haskell.org/ghc/>
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