DDEBUG build broken

Again, Travis is failing to build master since a while. Unfortunately, only the author of commits get mailed by Travis, so I did not notice it so far. But usually, when Travis reports a build failure, this is something actionable! If in doubt, contact me.

The breakage at the moment occurs only with -DDEBUG on:

    Compile failed (exit code 1) errors were:
    ghc-stage2: panic! (the 'impossible' happened)
      (GHC version 8.1.20161118 for x86_64-unknown-linux):
            No match in record selector is_iloc

    Please report this as a GHC bug:      https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.haskell.org%2Fghc%2Freportabug&data=02%7C01%7Csimonpj%40microsoft.com%7C688619e3295e4b6e0d5d08d41b0a2104%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636163177711116020&sdata=fh8XEV4Ioaxu0KkwKjDbweFvnQiNJ0V5%2BCj%2FQAdKvsY%3D&reserved=0


*** unexpected failure for rn017(normal) Compile failed (exit code 1) errors were:
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 8.1.20161118 for x86_64-unknown-linux):
        No match in record selector is_iloc

Please report this as a GHC bug:  https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.haskell.org%2Fghc%2Freportabug&data=02%7C01%7Csimonpj%40microsoft.com%7C688619e3295e4b6e0d5d08d41b0a2104%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636163177711116020&sdata=fh8XEV4Ioaxu0KkwKjDbweFvnQiNJ0V5%2BCj%2FQAdKvsY%3D&reserved=0


*** unexpected failure for T7672(normal)

And started appearing, unless I am mistaken, with

    From: Matthew Pickering <    matthewtpickering@gmail.com    >
    Date: Fri, 18 Nov 2016 16:28:30 +0000
    Subject: [PATCH] Optimise whole module exports

    We directly build up the correct AvailInfos rather than generating
    lots of singleton instances and combining them with expensive calls to
    unionLists.

    There are two other small changes.

    * Pushed the nubAvails call into the explicit export list
      branch as we construct them correctly and uniquely ourselves.
    * fix_faminst only needs to check the first element of the export
      list as we maintain the (yucky) invariant that the parent is the
      first thing in it.

    Reviewers: simonpj, austin, bgamari

    Reviewed By: simonpj, bgamari

    Subscribers: simonpj, thomie, niteria

    Differential Revision:     https://phabricator.haskell.org/D2657

Matthew, can you verify that this is a regression introduce here?

Greetings,
Joachim

The failing tests are rn017 and T7672.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture