testsuite/tests/simplCore/should_compile/simpl019.hs


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{-# LANGUAGE GADTs, FlexibleInstances #-}
{-# OPTIONS_GHC -O2 #-}

-- See #1746

module Foo where

data T a where T :: T a -> T [a]

class C a where
  f :: a -> ()

instance C (T [a]) where
  f (T x@(T _)) = f x