Any

A virtual type that encompasses all types and no types at the same time.

Default type

Any is the inferred type and return type when no type is explicitly annotated in a method. For example:

identity = _ -> _

is equivalent to:

identity = (_: Any): Any -> _

Using Any, be it implicitly or explicitly, disables type checking for an argument. The explicit annotation can be a useful in cases where you want to make it clear that you are giving flexibility in the type of a parameter.

Being too liberal with Any can make your code less predictable and harder to maintain. It's generally recommended to be more specific with type annotations whenever possible:

# Example of using Any that can lead to issues

console <- fat.console

doubleIt = (arg: Any): Void -> console.log(arg * 2)

doubleIt(2)    # prints: '4'
doubleIt('a')  # yields: Error: unsupported expression > Text <multiply> Number

This example shows that although the Any type annotation allows flexibility in the type of the argument, it can also result in unexpected behavior if a value of an unexpected type is passed in. By being more specific with the type annotation, such as Number, you can make your code more predictable and self-evident.

# Example of using a specific type annotation for more predictability

console <- fat.console

doubleIt = (num: Number): Void -> console.log(num * 2)

doubleIt(2)    # prints: '4'
doubleIt('a')  # yields: TypeError: type mismatch > num

By using Number as the type annotation, the doubleIt method is now more specific and only accepts arguments of type Number.

Comparisons

The only possible operation with Any is comparing to it, but note that Any accepts all values indistinctly, so there is no practical use for it:

null      == Any  # true
true      == Any  # true
12345     == Any  # true
'abcd'    == Any  # true
[ 1, 2 ]  == Any  # true
{ a = 8 } == Any  # true

comparisons with Any can't be used to check for the presence of a value in a scope as even null is accepted