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{-# LANGUAGE RoleAnnotations, FlexibleContexts #-}
unit p where
signature A where
type role T nominal
data T a = T
module B where
import Data.Coerce
import A
f :: Coercible (T a) (T b) => a -> b
f x = x
unit a where
module A where
data T a = T
unit q where
dependency p[A=a:A]
module C where
import B
g :: a -> b
g = f
-- Either:
-- a) B should fail to typecheck against the signature, or
-- b) A should fail to match against the signature
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