Hmm. Yes, this is an (actually harmless) assertion failure if your build has -DDEBUG on. I think it’s just a fluke that it’s only just started failing.
I’ll make a ticket for it; I don’t think it’s super-urgent.
Simon
From: ghc-devs [mailto:ghc-devs-bounces@
haskell.org ] On Behalf Of Simon Marlow
Sent: 09 November 2016 13:03
To: ghc-devs@haskell.org
Subject: T12041 failing?
I just saw the error below in a validate with -DDEBUG. Anyone know about this?--- /tmp/ghctest-uhJ8rt/test spaces/./indexed-types/should_fail/T12041.run/T12041.stderr. normalised 2016-11-09 12:13:38.206501840 +0000 +++ /tmp/ghctest-uhJ8rt/test spaces/./indexed-types/should_fail/T12041.run/T12041.comp. stderr.normalised 2016-11-09 12:13:38.206501840 +0000 @@ -1,7 +1,17 @@+ghc: panic! (the 'impossible' happened)+ (GHC version 8.1.20161109 for x86_64-unknown-linux):+ ASSERT failed!+ i_axb+ Call stack:+ CallStack (from HasCallStack):+ prettyCurrentCallStack, called at compiler/utils/Outputable.hs:<line>:<column> in <package-id>:Outputable + callStackDoc, called at compiler/utils/Outputable.hs:<line>:<column> in <package-id>:Outputable + assertPprPanic, called at compiler/typecheck/TcType.hs:<line>:<column> in <package-id>:TcType + Call stack:+ CallStack (from HasCallStack):+ prettyCurrentCallStack, called at compiler/utils/Outputable.hs:<line>:<column> in <package-id>:Outputable + callStackDoc, called at compiler/utils/Outputable.hs:<line>:<column> in <package-id>:Outputable + pprPanic, called at compiler/utils/Outputable.hs:<line>:<column> in <package-id>:Outputable + assertPprPanic, called at compiler/typecheck/TcType.hs:<line>:<column> in <package-id>:TcType -T12041.hs:12:15:- Expected kind ‘i -> Constraint’,- but ‘(~) Int’ has kind ‘* -> Constraint’- In the type ‘(~) Int’- In the type instance declaration for ‘Ob’- In the instance declaration for ‘Category I’+Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug *** unexpected failure for T12041(normal)