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OverloadedLists breaks exhaustiveness check

{-# LANGUAGE OverloadedLists #-}

module Bug where

f :: [a] -> ()
f x = case x of
  [] -> ()
  (_:_) -> ()

GHC reports:

bug.hs:6:7: Warning:
    Pattern match(es) are non-exhaustive
    In a case alternative: Patterns not matched: []

This is reproducible with 7.8 and 7.10rc1.

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