#5633: TypeFamilies don't seem to play with LIberalTypeSynonyms
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Reporter: ocharles | Owner:
Type: bug | Status: closed
Priority: normal | Milestone:
Component: Compiler | Version: 7.0.4
Resolution: invalid | Keywords: TypeFamilies
LiberalTypeSynonyms
Testcase: | Blockedby:
Difficulty: | Os: Linux
Blocking: | Architecture: x86
Failure: GHC rejects valid program |
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Comment(by ocharles):
Hi simon, thanks for the explanation.
It's a shame that it can't work, as a newtype doesn't really cut it. Fwiw,
the motivation of this ticket came from trying to abstract away Record
declarations in HaskellDB with code that also uses type families.
HaskellDB uses either `RecCons FieldType (Expr RetType)` or `RecCons
FieldType RetType` depending on how a record is used/returned, and there
doesn't seem to be a way to capture this with a type family, where I was
trying to abstract Expr :: * -> * away. However, this ticket isn't the
right place for that discussion, so I'll move that to a mailing list :)
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5633#comment:2>
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