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 Simon From: Thomas Miedema [mailto:thomasmiedema@gmail.com] Sent: 18 February 2016 18:41 To: Simon Peyton Jones ; ghc-devs@haskell.org Subject: Build failures with -DDEBUG Simon, 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: https://s3.amazonaws.com/archive.travis-ci.org/jobs/110115377/log.txthttps://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fs3.amazonaws.com%2farchive.travis-ci.org%2fjobs%2f110115377%2flog.txt&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7c4cc9af48558b4d699a0f08d3389306e2%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=Exe5inT9kmsMyourC2pWgynMt56p6UglF5lXqARY8E8%3d -- Thomas