System.BooleanType - Manhunter07/MFL GitHub Wiki
Declaration
const BooleanType = 2
Description
The BooleanType constant in the System package represents the type code for boolean values, represented by the True and False constants. It is returned when retrieving the type of either constant using the TypeOf function.
Other than the name might suggest, it is not a type but a constant. If you want to restrict function parameters to accept True or False only, use System.Boolean instead.