TFs: T2448

testsuite/tests/ghc-regress/indexed-types/should_compile/T2448.hs

+{-# 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)

testsuite/tests/ghc-regress/indexed-types/should_compile/all.T

@@ -119,3 +119,4 @@ test('OversatDecomp', normal, compile, [''])
 
 test('T2219', normal, compile, [''])
 test('T2627', normal, compile, [''])
+test('T2448', normal, compile, [''])