[ ghc-Bugs-699225 ] GHCi segfaults on expression evaluation

Bugs item #699225, was opened at 2003-03-07 06:21
Message generated for change (Comment added) made by simonmar
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=108032&aid=699225&group_id=8032

Category: None
Group: 5.04.2
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Carlos Eduardo Scheidegger (carlossch)
>Assigned to: Simon Peyton Jones (simonpj)
Summary: GHCi segfaults on expression evaluation

Initial Comment:
Hello. 

I think I've come across a GHCi bug.

Using the following module, GHCi version 5.04.2 segfaults, apparently trying to 
compute a type using functional dependencies. The segfault
happens when I try to calculate (v1 .> v2). I tried the code on Hugs, and it 
answers

Main> v1 .> v2
V [] :: PSOp (Pop a Id)

as expected. I think the problem is occuring in the line

> instance Reverse a b c => CheckPS Id a b c

because if I remove the line

> instance Reverse a (Pop t b)  c => Reverse (Pop t a) b c

instead of segfaulting, GHCi rightfully complains:

<interactive>:1:
    No instance for (Reverse (Pop a Id) Id c)
    arising from use of `.>' at <interactive>:1
    In the definition of `it': v1 .> v2


GHC compiles the program just fine and runs it without any issues. I installed 
GHC 5.04.2 using the RedHat 8.0 RPM's. If there's any important information you 
may need from me, please,  contact me through my email 
(carlos.scheidegger@xxxxxxxxxxxx), I'd be glad to be of help.

Carlos

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>Comment By: Simon Marlow (simonmar)
Date: 2003-04-23 13:17

Message:
Logged In: YES 
user_id=48280

This one is now fixed.

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Comment By: Carlos Eduardo Scheidegger (carlossch)
Date: 2003-03-07 06:29

Message:
Logged In: YES 
user_id=598005

I have just noticed that I mistakenly uploaded the file Test.hs without 
uncommenting the line

> instance Reverse a (Pop t b) ... 

GHCi only crashes with this line uncommented. I am sorry for the confusion

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