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)