panic when building ghc head

[Carter Schonwald]

hey all,
when doing a devel1 build  i got the following panic


"inplace/bin/genapply"
>rts/dist/build/AutoApply.cmm"inplace/bin/ghc-stage1" -static  -H64m
-O -fasm -Iincludes -Iincludes/dist
-Iincludes/dist-derivedconstants/header
-Iincludes/dist-ghcconstants/header -Irts -Irts/dist/build
-DCOMPILING_RTS -this-package-key rts -dcmm-lint  -DDTRACE     -i
-irts -irts/dist/build -irts/dist/build/autogen -Irts/dist/build
-Irts/dist/build/autogen           -O2    -c
rts/dist/build/AutoApply.cmm -o
rts/dist/build/AutoApply.o"inplace/bin/ghc-stage1" -fPIC -dynamic
-H64m -O -fasm -Iincludes -Iincludes/dist
-Iincludes/dist-derivedconstants/header
-Iincludes/dist-ghcconstants/header -Irts -Irts/dist/build
-DCOMPILING_RTS -this-package-key rts -dcmm-lint  -DDTRACE     -i
-irts -irts/dist/build -irts/dist/build/autogen -Irts/dist/build
-Irts/dist/build/autogen           -O2    -c
rts/dist/build/AutoApply.cmm -o
rts/dist/build/AutoApply.dyn_o"inplace/bin/ghc-stage1" -static
-eventlog  -H64m -O -fasm -Iincludes -Iincludes/dist
-Iincludes/dist-derivedconstants/header
-Iincludes/dist-ghcconstants/header -Irts -Irts/dist/build
-DCOMPILING_RTS -this-package-key rts -dcmm-lint  -DDTRACE     -i
-irts -irts/dist/build -irts/dist/build/autogen -Irts/dist/build
-Irts/dist/build/autogen           -O2    -c
rts/dist/build/AutoApply.cmm -o
rts/dist/build/AutoApply.l_o"inplace/bin/ghc-stage1" -static
-optc-DDEBUG -ticky -DTICKY_TICKY  -H64m -O -fasm -Iincludes
-Iincludes/dist -Iincludes/dist-derivedconstants/header
-Iincludes/dist-ghcconstants/header -Irts -Irts/dist/build
-DCOMPILING_RTS -this-package-key rts -dcmm-lint  -DDTRACE     -i
-irts -irts/dist/build -irts/dist/build/autogen -Irts/dist/build
-Irts/dist/build/autogen           -O2 -O0    -c
rts/dist/build/AutoApply.cmm -o rts/dist/build/AutoApply.debug_o***
Core Lint warnings : in result of Desugar (after optimization) ***{-#
LINE 101 "libraries/ghc-prim/GHC/Classes.hs #-}: Warning:
    [RHS of $c/=_a1qs :: GHC.Types.Float
                         -> GHC.Types.Float -> GHC.Types.Bool]
    INLINE binder is (non-rule) loop breaker: $c/=_a1qs{-# LINE 104
"libraries/ghc-prim/GHC/Classes.hs #-}: Warning:
    [RHS of $c/=_a1ql :: GHC.Types.Double
                         -> GHC.Types.Double -> GHC.Types.Bool]
    INLINE binder is (non-rule) loop breaker: $c/=_a1ql{-# LINE 85
"libraries/ghc-prim/GHC/Classes.hs #-}: Warning:
    [RHS of $c/=_a1qZ :: forall a_a1X.
                         GHC.Classes.Eq a_a1X =>
                         [a_a1X] -> [a_a1X] -> GHC.Types.Bool]
    INLINE binder is (non-rule) loop breaker: $c/=_a1qZ
ghc-stage1: panic! (the 'impossible' happened)
  (GHC version 7.9.20141018 for x86_64-apple-darwin):
	tyConAppTyCon a_12
Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

any ideas of how I could debug this? Or what it might be?
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