any.spad line 170 [edit on github]

This type is used when no value is needed, e.g. in the then part of a one armed if. All values can be coerced to type Void. Once a value has been coerced to Void, it cannot be recovered.

coerce: % -> OutputForm

coerce(v) coerces void object to OutputForm.

void: () -> %

void() produces a void object.