GHC 7.10.1 panic due to PartialTypeSignatures, TypeFamilies, and local bindings

{-# LANGUAGE PartialTypeSignatures #-}
{-# LANGUAGE TypeFamilies #-}
module Bad
where

foo f = g
  where g r = x
          where x :: _
                x = r

When compiled, it produces the following output:

[1 of 1] Compiling Bad              ( src/Bad.hs, src/Bad.o )

src/Bad.hs:8:22: Warning:
    Found hole ‘_’ with type: w_1
    Where: ‘w_1’ is a rigid type variable bound by
                 the inferred type of g :: w_1 -> w_1 at src/Bad.hs:7:9
    Relevant bindings include
      r :: w_1 (bound at src/Bad.hs:7:11)
      g :: w_1 -> w_1 (bound at src/Bad.hs:7:9)
      f :: t (bound at src/Bad.hs:6:5)
      foo :: t -> w_ -> w_ (bound at src/Bad.hs:6:1)
    In the type signature for ‘x’: _
    In an equation for ‘g’:
        g r
          = x
          where
              x :: _
              x = r
    In an equation for ‘foo’:
        foo f
          = g
          where
              g r
                = x
                where
                    x :: _
                    x = r
ghc: panic! (the 'impossible' happened)
  (GHC version 7.10.1 for x86_64-unknown-linux):
	StgCmmEnv: variable not found
  x_alC
  local binds for:
  f_sv5
  r_sv6

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

Trac metadata

Trac field	Value
Version	7.10.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	high
Resolution	Unresolved
Component	Compiler
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