[GHC] #1932: :type in ghci: impossible happened

[GHC]

#1932: :type in ghci: impossible happened
-------------------------+--------------------------------------------------
 Reporter:  joerisamson  |          Owner:         
     Type:  bug          |         Status:  new    
 Priority:  normal       |      Milestone:         
Component:  GHCi         |        Version:  6.8.1  
 Severity:  normal       |       Keywords:         
 Testcase:               |   Architecture:  Unknown
       Os:  Unknown      |  
-------------------------+--------------------------------------------------
 {{{
 GHCi, version 6.8.1: http://www.haskell.org/ghc/  :? for help
 Loading package base ... linking ... done.
 Prelude> let fac n = foldl (*) 1 [1..n]
 Prelude> :print fac
 fac = <function>
 ghc-6.8.1: panic! (the 'impossible' happened)
   (GHC version 6.8.1 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
 }}}

 This also happens with:
 {{{
 Prelude> let sum' a b = a+b
 Prelude> let product' a b = a*b
 Prelude> let sum' a b = (+) a b
 }}}
 but not with:
 {{{
 Prelude> let sum a b = a
 Prelude> :print sum
 sum = <function>
 Prelude> let summ a b = id b
 Prelude> :print summ
 summ = <function>
 Prelude> let id' x = x
 Prelude> :print id'
 id' = <function>
 Prelude> let product' = (*)
 Prelude> :print product'
 product' = <function>
 Prelude> let sum' = (+)
 Prelude> :print sum'
 sum' = <function>
 }}}

 All these functions do work properly when used in expressions

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1932>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler