werror.hs:6:1:
    Warning: Top-level binding with no type signature: main :: IO ()

werror.hs:7:13:
    Warning: This binding for `main' shadows the existing binding
               defined at werror.hs:6:1

werror.hs:7:13: Warning: Defined but not used: `main'

werror.hs:8:1: Warning: Tab character

werror.hs:10:1: Warning: Defined but not used: `f'

werror.hs:10:1:
    Warning: Top-level binding with no type signature:
               f :: forall t a. [t] -> [a]

werror.hs:10:1:
    Warning: Pattern match(es) are overlapped
             In an equation for `f': f [] = ...

werror.hs:10:1:
    Warning: Pattern match(es) are non-exhaustive
             In an equation for `f': Patterns not matched: _ : _

<no location info>: 
Failing due to -Werror.