Irrefutable pattern error while compiling GHC
While doing "make" on GHC HEAD I got this error:
"inplace/bin/ghc-stage1" -prof -H32m -O -package-name ghc-7.5.20120503 -hide-all-packages -i -icompiler/basicTypes -icompiler/cmm -icompiler/codeGen -icompiler/coreSyn -icompiler/deSugar -icompiler/ghci -icompiler/hsSyn -icompiler/iface -icompiler/llvmGen -icompiler/main -icompiler/nativeGen -icompiler/parser -icompiler/prelude -icompiler/profiling -icompiler/rename -icompiler/simplCore -icompiler/simplStg -icompiler/specialise -icompiler/stgSyn -icompiler/stranal -icompiler/typecheck -icompiler/types -icompiler/utils -icompiler/vectorise -icompiler/stage2/build -icompiler/stage2/build/autogen -Icompiler/stage2/build -Icompiler/stage2/build/autogen -Icompiler/../rts/dist/build -Icompiler/stage2 -Icompiler/. -Icompiler/parser -Icompiler/utils -optP-DGHCI -optP-include -optPcompiler/stage2/build/autogen/cabal_macros.h -package Cabal-1.14.0 -package array-0.3.0.3 -package base-4.5.0.0 -package bin-package-db-0.0.0.0 -package bytestring-0.10.0.0 -package containers-0.5.0.0 -package directory-1.1.0.1 -package filepath-1.2.0.1 -package hoopl-3.8.7.2 -package hpc-0.5.1.0 -package process-1.1.0.0 -package template-haskell-2.6.0.0 -package time-1.4 -package unix-2.5.1.0 -Wall -fno-warn-name-shadowing -fno-warn-orphans -XHaskell98 -XNondecreasingIndentation -XCPP -XMagicHash -XUnboxedTuples -XPatternGuards -XForeignFunctionInterface -XEmptyDataDecls -XTypeSynonymInstances -XMultiParamTypeClasses -XFlexibleInstances -XRankNTypes -XScopedTypeVariables -XDeriveDataTypeable -XBangPatterns -DGHCI_TABLES_NEXT_TO_CODE -DSTAGE=2 -O2 -no-user-package-conf -rtsopts -odir compiler/stage2/build -hidir compiler/stage2/build -stubdir compiler/stage2/build -hisuf p_hi -osuf p_o -hcsuf p_hc -c compiler/main/HscMain.hs -o compiler/stage2/build/HscMain.p_o
ghc-stage1: panic! (the 'impossible' happened)
(GHC version 7.5.20120503 for x86_64-apple-darwin):
compiler/simplCore/SimplUtils.lhs:1668:5-25: Irrefutable pattern failed for pattern ((_, _, rhs1) : _)
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
make[1]: *** [compiler/stage2/build/HscMain.p_o] Error 1
make: *** [all] Error 2