ByteString builder causes the optimiser to run out of ticks

I received the following error message from GHC:

<no location info>:
    ghc: panic! (the 'impossible' happened)
  (GHC version 7.10.3 for x86_64-unknown-linux):
	Simplifier ticks exhausted
  When trying UnfoldingDone $fStorableWord21
  To increase the limit, use -fsimpl-tick-factor=N (default 100)
  If you need to do this, let GHC HQ know, and what factor you needed
  To see detailed counts use -ddump-simpl-stats
  Total ticks: 8040

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

When I followed the suggestion of adding -fsimpl-tick-factor=200 the compiler proceeds normally (finding a syntax error in a file). Removing this option, strangely, also causes the compiler to proceed normally. I can no longer reproduce this bug, although several compilations in a row (before adding the option) reproduced the bug.

Although I cannot reproduce this bug, the syntax error that is present came from an error of the form:

f :: A -> M B
f a = 
  do
    x <- g a
  let
    c = h a
  in do
    ...

The actual file is attached.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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