#4246: "Conflicting family instance declarations" error mentions code I did not
write
---------------------------------+------------------------------------------
Reporter: TillmannRendel | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.12.1 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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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.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4246>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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