Opened 9 years ago

Closed 9 years ago

#3418 closed bug (fixed)

Equality constraint causes ghc panic

Reported by: blarsen Owned by: chak
Priority: normal Milestone:
Component: Compiler Version: 6.10.4
Keywords: type families, equality constraint, panic Cc: brad.larsen@…
Operating System: Linux Architecture: x86_64 (amd64)
Type of failure: None/Unknown Test Case: T3418
Blocked By: Blocking:
Related Tickets: Differential Rev(s):
Wiki Page:


I have the following module:

{-# LANGUAGE TypeFamilies #-}
module GhcBug where

newtype (a ~ b) => S a b = S { unS :: a }

Loading this in ghci results in this:

> :l GhcBug
[1 of 1] Compiling GhcBug           ( GhcBug.hs, interpreted )
ghc: panic! (the 'impossible' happened)
  (GHC version 6.10.4 for x86_64-unknown-linux):
	typePrimRep <pred>a{tv a1MH} [tv] ~ b{tv a1MI} [tv]

Please report this as a GHC bug:

Change History (2)

comment:1 Changed 9 years ago by chak

Owner: set to chak

comment:2 Changed 9 years ago by chak

Resolution: fixed
Status: newclosed
Test Case: T3418

Fixed in the head by one of the recent changes.

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