id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
5837	Context reduction stack overflow can take very long	dreixel	simonpj	"The following code, taken from the ""Haskell Type Constraints Unleashed"" paper:
{{{
{-# LANGUAGE TypeFamilies #-}

type family TF a :: *
type instance TF (a,b) = (TF a, TF b)

t :: (a ~ TF (a,Int)) => Int
t = undefined
}}}
fails almost immediately with `Context reduction stack overflow` on GHC 7.2, but seems to loop forever with 7.4.1-rc2. Setting `-fcontext-stack` to `20` results in near immediate termination with the same error. But #5395 raised the context stack size default to `200`, which makes this code (that does not use `-XUndecidableInstances`) take ""forever"" to compile.
"	bug	closed	normal	7.6.1	Compiler (Type checker)	7.4.1-rc2	fixed			Unknown/Multiple	Unknown/Multiple	None/Unknown	Unknown	perf/compiler/T5837