id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
4246	"""Conflicting family instance declarations"" error mentions code I did not write"	TillmannRendel		"I get an error message mentioning code that I did not write but results from desugaring when compiling the following program:

{{{
{-# LANGUAGE TypeFamilies, FlexibleInstances, OverlappingInstances #-}

class Stupid a where
  type F a

instance Stupid a where
  type F a = a

instance Stupid Int where
  type F Int = Bool
}}}

The error I get is:
{{{
families.hs:7:7:
    Conflicting family instance declarations:
      type instance F a -- Defined at families.hs:7:7
      type instance F Int -- Defined at families.hs:10:7
}}}

The error mentions ""type instance F a"", but it should say ""type F a"", because that is what I wrote in the source file. Or maybe ""type F a in instance Stupid a"" to make it clear that it's an instance declaration."	bug	closed	normal	7.4.1	Compiler	6.12.1	fixed		rendel@… p.giarrusso@…	Unknown/Multiple	Unknown/Multiple	None/Unknown		indexed-types/should_fail/T4246