In Haskell, `sum` adds a collection of numbers, i.e. instances of the Num typeclass:

    Prelude> sum ["a", "b"]

    <interactive>:4:1: error:
    • No instance for (Num [Char]) arising from a use of ‘sum’
    • In the expression: sum ["a", "b"]
      In an equation for ‘it’: it = sum ["a", "b"]

You appear to be refuting a straw man.