(mixin ..forms)
  forms: zero or more forms

Applies mixins to a class definition.

When the class clause is evaluated, each of the forms are evaluated in order, from left to right. They must each return a class which was previously defined using the mixin macro. The definitions of those classes are "mixed into" the new class which is being defined.

This means that:

• Any states defined by the mixins are effectively copied-and-pasted at the beginning of the class definition. Name collisions between states are forbidden.
• Any fields, constants, methods and properties, including wrappers, are copied into the toplevel of the class definition. Their fully-qualified name is MixinName:item, rather than the usual Main:item. Name collisions are forbidden; mixins do not participate in shadowing.
• The mixin's init-mixin clause, if any, will act as a wrapper method for the class' init method.
• The mixin's fini-mixin clause, if any, will be invoked after the class' fini method.