Splicing a type into a signature decl within a decl quotation panics with "mkUsageInfo: internal name? x2{v a2pX}"

Hello,

trying to compile the attached file gives:

[1 of 1] Compiling THUtil           ( THUtil.hs, THUtil.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.0.3 for i386-unknown-linux):
        mkUsageInfo: internal name? x2{v a1Jh}

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

Trac metadata

Trac field	Value
Version	7.0.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
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