BadSock triggers failing ASSERT

--- ./indexed-types/should_fail/BadSock.stderr.normalised	2015-09-18 20:44:48.437390831 +0000
+++ ./indexed-types/should_fail/BadSock.comp.stderr.normalised	2015-09-18 20:44:48.437390831 +0000
@@ -1,5 +1,5 @@
+ghc: panic! (the 'impossible' happened)
+  (GHC version 7.11.20150918 for x86_64-unknown-linux):
+	ASSERT failed! file compiler/typecheck/TcFlatten.hs, line 1041
 
-BadSock.hs:30:5:
-    The type family ‘Readable’ should have 1 argument, but has been given none
-    In the equations for closed type family ‘Foo’
-    In the type family declaration for ‘Foo’
\ No newline at end of file
+Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
\ No newline at end of file
*** unexpected failure for BadSock(normal)

Haven't investigated any further.

Trac metadata

Trac field	Value
Version	7.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	goldfire
Operating system
Architecture