Ticket #1323 (closed bug: wontfix)
crash when zipping two lists of the same length...
Description (last modified by simonpj) (diff)
I've personally not checked this against 6.6.1, but "mauke" on #haskell says the same crash and same line number appears in the crash report.
$ ghc --version The Glorious Glasgow Haskell Compilation System, version 6.6 $ ghc -v --make Session.hs Glasgow Haskell Compiler, Version 6.6, for Haskell 98, compiled by GHC version 6.6 Using package config file: /usr/lib/ghc-6.6/package.conf hiding package hinstaller-2007.4.21 to avoid conflict with later version hinstaller-2007.4.24 wired-in package base mapped to base-2.0 wired-in package rts mapped to rts-1.0 wired-in package haskell98 mapped to haskell98-1.0 wired-in package template-haskell mapped to template-haskell-2.0 Hsc static flags: -static *** Chasing dependencies: Chasing modules from: Session.hs Stable obj:  Stable BCO:  compile: input file Session.hs Created temporary directory: /tmp/ghc4588_0 *** Checking old interface for main:Main: [1 of 1] Compiling Main ( Session.hs, Session.o ) *** Parser: *** Renamer/typechecker: *** Desugar: Result size = 379 *** Simplify: *** Deleting temp files: Deleting: /tmp/ghc4588_0/ghc4588_0.s Warning: deleting non-existent /tmp/ghc4588_0/ghc4588_0.s *** Deleting temp dirs: Deleting: /tmp/ghc4588_0 ghc-6.6: panic! (the 'impossible' happened) (GHC version 6.6 for x86_64-unknown-linux): Pattern match failure in do expression at simplCore/Simplify.lhs:1540:8-21 Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
Now as the comments in the source say, it works fine if you replace newtype with data, and I am aware that there are differences in what they do, though I can never quite remember the fine details. So it's quite possibly my fault, but an error message other than a GHC crash would be nicer!