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{-# LANGUAGE TypeFamilies, UndecidableInstances #-}
module T2448 where
-- Demonstrates a bug in propagating type equality constraints
class VectorSpace v where
type Scalar v :: *
class VectorSpace v => InnerSpace v
instance (VectorSpace u,VectorSpace v, Scalar u ~ Scalar v) =>
VectorSpace (u,v)
where
type Scalar (u,v) = Scalar u
instance (InnerSpace u,InnerSpace v, Scalar u ~ Scalar v) => InnerSpace (u,v)
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