Assertion failed with BuildFlavour = devel2 (yet another)

Still trying to debug compilation failures in our codebase, still can't build prerequisites yet.

ghc needs to be compiled with BuildVlavour = devel2 and compilation with -O2 is required:

{-# LANGUAGE GeneralizedNewtypeDeriving #-}

module A where

import Data.List(minimumBy)
import Data.Ord (comparing)

data A a = A Int

newtype B = B Double deriving (Eq,Ord,Num,Real,Fractional,RealFrac,Floating,RealFloat)

class C a where
    _c :: [a] -> D a

instance C B where
    _c = f2 u
                             
                             
data D x = D [(x,Double)] [ x ]
    

u = undefined

f1 :: RealFloat a => A a -> a -> [a] -> D a
f1 (A a1) m ps0 = D (zip tickvs []) labelvs
  where
  
    range _ | m == m = if m==0 then (-1,1) else (m, m)
    labelvs   = map fromRational $ f3 (fromIntegral a1) (range ps0)
    tickvs    = map fromRational $ f3 (fromIntegral a1) (head labelvs, head labelvs)
    
f2 :: RealFloat a => A a -> [a] -> D a
f2 lap ps = f1 u (minimum ps) ps

f3 :: RealFloat a => a -> (a,a) -> [Rational]
f3 k rs@(m,_ ) = map ((s*) . fromIntegral) [floor m .. ]
  where
    s = minimumBy (comparing ((+ k) . realToFrac)) [0]

% ghc -O2 A.hs 
[1 of 1] Compiling A                ( A.hs, A.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 8.0.1 for x86_64-unknown-linux):
        ASSERT failed!
  CallStack (from HasCallStack):
  assertPprPanic, called at compiler/types/TyCoRep.hs:1978:56 in ghc:TyCoRep
  checkValidSubst, called at compiler/types/TyCoRep.hs:2014:17 in ghc:TyCoRep
  substTy, called at compiler/types/Coercion.hs:1454:33 in ghc:Coercion
  in_scope InScope [00 :-> wild_00, X1o :-> wild_X1o,
                    X1p :-> wild_X1p, a4z5 :-> $c==_a4z5, a4zs :-> $c/=_a4zs,
                    a4zV :-> $ccompare_a4zV, a4Ai :-> $c<_a4Ai, a4AF :-> $c<=_a4AF,
                    a4B2 :-> $c>_a4B2, a4Bp :-> $c>=_a4Bp, a4BM :-> $cmax_a4BM,
                    a4C9 :-> $cmin_a4C9, a4Cy :-> $c+_a4Cy, a4CV :-> $c-_a4CV,
                    a4Di :-> $c*_a4Di, a4DF :-> $cnegate_a4DF, a4DY :-> $cabs_a4DY,
                    a4Eh :-> $csignum_a4Eh, a4EA :-> $cfromInteger_a4EA,
                    a4F3 :-> $ctoRational_a4F3, a4Fs :-> $c/_a4Fs,
                    a4FP :-> $crecip_a4FP, a4G8 :-> $cfromRational_a4G8,
                    a4GB :-> $cproperFraction_a4GB, a4Hg :-> $ctruncate_a4Hg,
                    a4HV :-> $cround_a4HV, a4IA :-> $cceiling_a4IA,
                    a4Jf :-> $cfloor_a4Jf, a4K0 :-> $cpi_a4K0, a4Kf :-> $cexp_a4Kf,
                    a4Ky :-> $clog_a4Ky, a4KR :-> $csqrt_a4KR, a4La :-> $c**_a4La,
                    a4Lx :-> $clogBase_a4Lx, a4LU :-> $csin_a4LU, a4Md :-> $ccos_a4Md,
                    a4Mw :-> $ctan_a4Mw, a4MP :-> $casin_a4MP, a4N8 :-> $cacos_a4N8,
                    a4Nr :-> $catan_a4Nr, a4NK :-> $csinh_a4NK, a4O3 :-> $ccosh_a4O3,
                    a4Om :-> $ctanh_a4Om, a4OF :-> $casinh_a4OF, a4OY :-> $cacosh_a4OY,
                    a4Ph :-> $catanh_a4Ph, a4PA :-> $clog1p_a4PA,
                    a4PT :-> $cexpm1_a4PT, a4Qc :-> $clog1pexp_a4Qc,
                    a4Qv :-> $clog1mexp_a4Qv, a4QY :-> $cfloatRadix_a4QY,
                    a4Rh :-> $cfloatDigits_a4Rh, a4RA :-> $cfloatRange_a4RA,
                    a4RT :-> $cdecodeFloat_a4RT, a4Sc :-> $cencodeFloat_a4Sc,
                    a4Sz :-> $cexponent_a4Sz, a4SS :-> $csignificand_a4SS,
                    a4Tb :-> $cscaleFloat_a4Tb, a4Ty :-> $cisNaN_a4Ty,
                    a4TR :-> $cisInfinite_a4TR, a4Ua :-> $cisDenormalized_a4Ua,
                    a4Ut :-> $cisNegativeZero_a4Ut, a4UM :-> $cisIEEE_a4UM,
                    a4V5 :-> $catan2_a4V5, a4Vu :-> $c_c_a4Vu, a5eH :-> wild_a5eH,
                    a5eJ :-> x_a5eJ, ruN :-> u, ruO :-> f1, ruP :-> f2, ruQ :-> f3,
                    r24E :-> $tc'A, r25L :-> $tcA, r25N :-> $tc'B, r25Z :-> $tcB,
                    r2dl :-> $tc'D, r2ds :-> $tcD, r2dF :-> $tcC, r2dG :-> $tc'C:C,
                    r2dL :-> $fCB, r2dZ :-> $fEqB, r2ec :-> $fOrdB, r2nC :-> $fNumB,
                    r2nK :-> $fRealB, r2nT :-> $fFractionalB, r2oa :-> $fRealFracB,
                    r2oC :-> $fFloatingB, r2oX :-> $fRealFloatB, r4yJ :-> $trModule,
                    s5iM :-> $trModule_s5iM, s5iN :-> $trModule_s5iN,
                    s5iO :-> $tc'A_s5iO, s5iQ :-> $tc'B_s5iQ, s5iR :-> $tcB_s5iR,
                    s5iS :-> $tc'D_s5iS, s5iT :-> $tcD_s5iT, s5iU :-> $tc'C:C_s5iU,
                    s5iV :-> $tcC_s5iV, s5jw :-> $sf2_s5jw, s5jM :-> $sf1_s5jM,
                    s5jU :-> labelvs_s5jU, s5k8 :-> $sf3_s5k8,
                    s5ki :-> $sfromIntegral_s5ki, s5kD :-> $sminimum_s5kD,
                    s5kE :-> $scomparing_s5kE, s5kF :-> $srealToFrac_s5kF,
                    s5kG :-> $sfromIntegral_s5kG, s5kN :-> lvl_s5kN, s5kX :-> lvl_s5kX,
                    s5lc :-> lvl_s5lc, s5ln :-> lvl_s5ln, s5pu :-> lvl_s5pu,
                    s5pv :-> lvl_s5pv, s5ra :-> lvl_s5ra, s5rb :-> lvl_s5rb,
                    s5Bi :-> $w$sf3_s5Bi, s5Bt :-> $wf3_s5Bt, s5Bx :-> w_s5Bx,
                    s5BB :-> ww_s5BB, s5BF :-> $w$sf1_s5BF, s5BS :-> $wf1_s5BS,
                    s5BW :-> $wf2_s5BW, s5D0 :-> $j_s5D0, s5FJ :-> lvl_s5FJ,
                    s5FL :-> $wgo_s5FL, s5FM :-> lvl_s5FM, s5FN :-> lvl_s5FN,
                    s5FP :-> karg_s5FP, s5FW :-> go_s5FW, s5FX :-> lvl_s5FX,
                    s5FY :-> lvl_s5FY, s5FZ :-> lvl_s5FZ, s5G0 :-> lvl_s5G0,
                    s5G1 :-> lvl_s5G1, s5G2 :-> lvl_s5G2, s5G4 :-> lvl_s5G4,
                    s5G5 :-> lvl_s5G5, s5G6 :-> lvl_s5G6, s5G7 :-> lvl_s5G7,
                    s5Io :-> $s$j_s5Io, s5Ip :-> $s$j_s5Ip, s5Ir :-> $sgo_s5Ir]
  tenv []
  tenvFVs []
  cenv [s5Ij :-> sg_s5Ij, s5Ik :-> sg_s5Ik]
  cenvFVs [s5Ij :-> sg_s5Ij, s5Ik :-> sg_s5Ik]
  tys [Ratio Integer]
  cos []

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

Trac metadata

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