panic in T7562

Various people observe this test failure:

=====> T7562(normal) 869 of 4389 [0, 0, 0] 
cd ./typecheck/should_compile && '/home/jojo/build/haskell/ghc-validate/inplace/bin/ghc-stage2' -fforce-recomp -dcore-lint -dcmm-lint -dno-debug-output -no-user-package-db -rtsopts -fno-warn-tabs -fno-ghci-history -c T7562.hs   -fno-warn-incomplete-patterns >T7562.comp.stderr 2>&1
Compile failed (status 256) errors were:

T7562.hs:3:14: Warning:
    UNPACK pragma lacks '!' on the first argument of ‘Pair2’
    In the definition of data constructor ‘Pair2’
    In the data declaration for ‘Pair2’
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.11.20150108 for x86_64-unknown-linux):
	toIfaceBang

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

According to my logs, this was caused by changeset:9564bb8c/ghc

Trac metadata

Trac field	Value
Version	7.8.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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