Build failures with -DDEBUG

Simon Peyton Jones simonpj at
Thu Feb 18 19:10:23 UTC 2016

Very helpful thanks.  TcCoercibleFail is known to time out (for decent reasons) with –DDEBUG (see comments in the dsource file)

I’l look into the PatSyn thing


From: Thomas Miedema [mailto:thomasmiedema at]
Sent: 18 February 2016 18:41
To: Simon Peyton Jones <simonpj at>; ghc-devs at
Subject: Build failures with -DDEBUG


the commits you pushed today don't validate with -DDEBUG.

Unexpected failures:

   patsyn/should_compile  MoreEx [exit code non-0] (normal)

   patsyn/should_compile  T11224b [exit code non-0] (normal)

   polykinds              MonoidsTF [exit code non-0] (normal)

   polykinds              T11480b [exit code non-0] (normal)

   polykinds              T11523 [exit code non-0] (normal)

   typecheck/should_fail  TcCoercibleFail [stderr mismatch] (normal)

TcCoercibleFail timed out, and the others all hit the following debug assert:

=====> T11224b(normal) 2510 of 5029 [0, 0, 0]
Compile failed (status 256) errors were:
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 8.1.20160218 for x86_64-unknown-linux):
          ASSERT failed!
  CallStack (from HasCallStack):
  assertPprPanic, called at compiler/types/TyCoRep.hs:1932:56 in ghc:TyCoRep
  checkValidSubst, called at compiler/types/TyCoRep.hs:1991:17 in ghc:TyCoRep
  substTys, called at compiler/types/TyCoRep.hs:2012:14 in ghc:TyCoRep
  substTheta, called at compiler/typecheck/TcPatSyn.hs:255:20 in ghc:TcPatSyn
  in_scope InScope {d_ap0 c_apv}
  tenv [ap1 :-> c_apv[tau:5]]
  tenvFVs [aps :-> t_aps[tau:1], apv :-> c_apv[tau:5]]
  cenv []
  cenvFVs []
  tys []
  cos []

Complete log from Travis:<>

-- Thomas
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