Function validate_argument 

fn validate_argument(
    arg: &CodeArg,
    data: &Everything,
    sc: &mut ScopeContext,
    dc: &DataContext,
    expect_arg: Arg,
    lang: Option<Language>,
    format: Option<&Token>,
)

Internal function for validating an argument to a datatype code. If the argument is iself a code chain, this will end up calling validate_datatypes recursively.

• arg: The actual argument being supplied.
• sc: The available named scopes.
• expect_arg: The form of argument expected by the promote or function.
• lang: The language of the localization file in which this code appears. This is just passed through.
• format: The formatting code for this code chain. This just passed through.