semantic equivalence of f() <=> f(undefined) and so on

[drsm]

The subject is broken in many places, i.e. #5 or:

>> 2..toString()
2
>> 2..toString(void 0)
RangeError
    at Number.prototype.toString (native)
    at main (native)

[xeioex]

@drsm Can you, please, give me the link to the specification which requires this behavior for every function?

[drsm]

@xeioex i'll try to find out. but, i think it is a "common behavior", rather than requirement. my point is that if no special care has been taken to differentiate a call without an argument specified and a call with undefined(void) argument provided, then results of both calls should be the same. otherwise there will be inconsistencies between internal and user-defined functions.

>> function id(x) { return x; }
undefined
>> id() === id(void 0)
true
>> (function wrapfail(x) { return 2..toString(x); })()
RangeError
    at Number.prototype.toString (native)
    at anonymous (:1)
    at main (native)

also, if we want to implement the "default function parameters" feature, let's consider this sample:

> function defaults(x = 10) { return x; }
undefined
> defaults() === defaults(void 0)
true

and finally, all of [V8, Firefox, JJS] engines demonstrate the same behavior.

[drsm]

here it is:
https://www.ecma-international.org/ecma-262/5.1/#sec-10.5

4.d.ii If n is greater than argCount, let v be undefined otherwise let v be the value of the n’th element of args.