Will attach two files to this bug, quasi-arithmetic.hs and QuasiArith.hs.

Running:

ghc --make quasi-arithmetic.hs -o quasi-arithmetic

on these files results in:

ghc: panic! (the 'impossible' happened)
  (GHC version 7.4.2 for x86_64-unknown-linux):
        mkUsage
    main:QuasiArith BinopExpr{d}[(0B, base:System.IO.print{v 0B}),
                                  (32I, ghc-prim:GHC.Types.IO{tc 32I}),
                                  (40, ghc-prim:GHC.Tuple.(){(w) tc 40}),
                                  (rwP, main:QuasiArith.MulOp{d rwP}),
                                  (rwR, main:QuasiArith.AddOp{d rwR}),
                                  (rwU, main:QuasiArith.BinopExpr{d rwU}),
                                  (rwW, main:QuasiArith.IntExpr{d rwW}),
                                  (r2Ha, main:Main.main{v r2Ha})]