MOP addPrototype: #MetaClosure derivedFrom: {MOP MetaObject}.
MOP MetaClosure addSlot: #typeSignature.
MOP MetaClosure addSlot: #arity. "The number of arguments."

MOP addPrototype: #MetaMethod derivedFrom: {MOP MetaClosure}.
MOP MetaMethod addSlot: #dispatchSignature.

name@(Symbol traits) findSignatureOn: args
"Returns a collection of the objects on which the first-applicable method is
defined for the given arguments."
[| result |
  result: (args newSizeOf: args).
  args doWithIndex:
    [| :each :index |
     ].
  result
].