Serialization of EFun objects for exported functions isn't implemented

[eriksoe]

==== Current behaviour: 1> erlang:term_to_binary(fun erlang:'not'/1). \ exception error: {not_implemented,"Encode for erjang.m.erlang.ErlBif$FN_not__1", "erjang.EObject.encode(EObject.java:435)"}

==== Desired behaviour: Function objects for exported functions should be serialized using EOutputStream.write_external_fun(module, function, arity).

[eriksoe]

At present, the EFun objects for exported functions do not contain their module and function name except as encoded in the class name.

Related, EFun subclasses for closures contain much code which could be moved to a common superclass for all similar closures:

• fields index, old_index, pid, and fv1..fvN.
• get_pid(), get_id(), get_env() and encode()

I suggest that common superclasses be introduced:

• For exported functions of arity N: EFun{N}_Exported extends EFun{N} (with fields containing module name and function name, and a constructor populating both; and the method encode().).
• For closures of arity N with M free variables: EFun{N}_Closure{M} extends EFun{N} (with fields index, old_index, pid, and fv1..fvM and an appropriate constructor; and methods get_pid(), get_id(), get_env() and encode().)

In addition to solving the present issue for exported functions, class sizes (and possibly module loading time?) would be reduced.

[eriksoe]

Note that while erlang:term_to_binary(fun erlang:'not'/1). fails, an equivalent function object can be encoded: erlang:term_to_binary(fun(X)->erlang:'not'(X) end). with success. (This is due to encode() being code generated for all local functions but for none of the exported ones.)

[eriksoe]

Implemented (along with common superclasses for exported functions).