GHC craches on this combination of ViewPatterns and PatternSynonyms

The attached file crashes:

$ ghc Bug.hs 
[1 of 1] Compiling Bug              ( Bug.hs, Bug.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.10.2 for x86_64-unknown-linux):
	Prelude.last: empty list

I wasn't able to shrink the example further despite many attepts.

Tested on GHC 7.8.3 and 7.10.2.

Trac metadata

Trac field	Value
Version	7.10.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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