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  • #9269

Closed
Open
Opened Jul 05, 2014 by pumpkin@trac-pumpkin

Type families returning quantified types

Is there a fundamental reason for not being able to use quantification in a type family? I'd very much like to be able to do it, obviously turning on RankNTypes if necessary.

I'm looking for things like this:

type family Foo (x :: Bool) where
  Foo True = forall a. [a]
  Foo False = ()
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Version 7.8.2
Type FeatureRequest
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
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Reference: ghc/ghc#9269