#3046: Generalized newtype deriving with associated types
-----------------------------+----------------------------------------------
Reporter: LouisWasserman | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.10.1 | Severity: normal
Keywords: | Testcase:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
-----------------------------+----------------------------------------------
When I have a
{{{
class Foo a where
type Bar a
foobar :: a -> Bar a
}}}
an
{{{
instance Foo Fooey ...
}}}
and
{{{
newtype Fooey2 = F2 (Fooey) deriving (Foo)
}}}
I expect the automatically generated deriving to include
{{{
type Bar Fooey2 = Bar Fooey
}}}
but this is not the case: I cannot get an associated type from a newtype
to resolve to anything. My guess is that the combination of
-XTypeFamilies and -XGeneralizedNewtypeDeriving is rare enough that this
may simply not have been thought of yet, but it's something I'd like to
see fixed.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3046>
GHC <http://www.haskell.org/ghc/>
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