Invalid core generated with GHC 7.10 RC3

Using the Shake repo (https://github.com/ndmitchell/shake.git) at commit d7fa04 and GHC 7.10 RC3 or GHC HEAD, if I {{cabal test}} I get the error:

## BUILD oracle --quiet *str-int
TESTS FAILED
shake-test: Expected an exception but succeeded

Discussion about this issue can be found on the mailing list: http://osdir.com/ml/general/2015-03/msg25847.html

GHC generates the Core:

case (\_ -> error "here") of {}

This is invalid GHC Core. I intend to track down a minimal example shortly.

Trac metadata

Trac field	Value
Version	7.8.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	high
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	ndmitchell@gmail.com
Operating system
Architecture