head of empty list in haskell

a.hs

main = print $ show $ head []

run

> nix-shell -p ghc --run 'ghc a.hs'
[1 of 1] Compiling Main             ( a.hs, a.o )

a.hs:1:16: error:
    • Ambiguous type variable ‘a0’ arising from a use of ‘show’
      prevents the constraint ‘(Show a0)’ from being solved.
      Probable fix: use a type annotation to specify what ‘a0’ should be.
      These potential instances exist:
        instance Show Ordering -- Defined in ‘GHC.Show’
        instance Show Integer -- Defined in ‘GHC.Show’
        instance Show a => Show (Maybe a) -- Defined in ‘GHC.Show’
        ...plus 22 others
        ...plus five instances involving out-of-scope types
        (use -fprint-potential-instances to see them all)
    • In the second argument of ‘($)’, namely ‘show $ head []’
      In the expression: print $ show $ head []
      In an equation for ‘main’: main = print $ show $ head []
> nix-shell -p ghc --run 'ghc -e "print $ show $ head []"'
<interactive>: Prelude.head: empty list