This looks like a great opportunity to try out the new holes functionality:

[Prelude] λ [] == _what

<interactive>:3:7:

    Found hole ‘_what’ with type: [t0]

    Where: ‘t0’ is an ambiguous type variable

    Relevant bindings include it :: Bool (bound at <interactive>:3:1)

    In the second argument of ‘(==)’, namely ‘_what’

    In the expression: [] == _what

    In an equation for ‘it’: it = [] == _what

Looks like it defaults to [Bool]!

Correct me if I'm wrong :)