#3392 — toMethod should create a function without a prototype property

bug_id: 3392
creation_ts: 2014-11-19 15:51:00 -0800
short_desc: toMethod should create a function without a prototype property
delta_ts: 2015-07-10 08:34:19 -0700
product: Draft for 7th Edition
component: New feature suggestons
version: unspecified
rep_platform: All
op_sys: All
bug_status: CONFIRMED
priority: Normal
bug_severity: normal
everconfirmed: true
reporter: Erik Arvidsson
assigned_to: Allen Wirfs-Brock
cc: ["andrebargull", "dslomov", "erik.arvidsson"]

commentid: 10664
comment_count: 0
who: Erik Arvidsson
bug_when: 2014-11-19 15:51:48 -0800

Since methods do not have a prototype property, Function.prototype.toMethod should also create a function without a prototype property.

function f() {}
assert(f.hasOwnProperty('prototype'));
var g = f.toMethod({});
assert(!g.hasOwnProperty('prototype'));

It is not clear to me if the spec is handling this or not?

commentid: 10665
comment_count: 1
who: André Bargull
bug_when: 2014-11-20 03:52:42 -0800

(In reply to Erik Arvidsson from comment #0)
> It is not clear to me if the spec is handling this or not?

Steps 4-6 in 9.2.12 CloneMethod cover this case. Only internal methods and internal slots are copied over, including non-standard internal slots (bug 2012). "copied over" is possibly the wrong choice of words, because the internal slot values are not copied as in "a new copy of the value is created", but instead the value of each internal slot is set to the value of the corresponding internal slot of the original object.

The note after 9.2.12 explains this, too (The part about "restricted function properties" still needs to be removed - bug 3345). Unfortunately that note is on the next page in the pdf version, so it's easy to miss.

commentid: 10704
comment_count: 2
who: Allen Wirfs-Brock
bug_when: 2014-12-03 12:06:55 -0800

(In reply to André Bargull from comment #1)
> (In reply to Erik Arvidsson from comment #0)
> > It is not clear to me if the spec is handling this or not?
>
> Steps 4-6 in 9.2.12 CloneMethod cover this case. Only internal methods and
> internal slots are copied over, including non-standard internal slots (bug
> 2012). "copied over" is possibly the wrong choice of words, because the
> internal slot values are not copied as in "a new copy of the value is
> created", but instead the value of each internal slot is set to the value of
> the corresponding internal slot of the original object.
>
> The note after 9.2.12 explains this, too (The part about "restricted
> function properties" still needs to be removed - bug 3345). Unfortunately
> that note is on the next page in the pdf version, so it's easy to miss.

However, this means that if the function has a [[Construct]] internal method it will now use Object.prototype as the prototype for new instances.

I guess the moral of the story is that you really need to code something like:
var g = Object.mixin(f.toMethod(obj), f);

Except we don't have Object.mixin any more!

commentid: 12097
comment_count: 3
who: Allen Wirfs-Brock
bug_when: 2015-02-04 10:02:47 -0800

moved to deferred features because toMethod has been deferred

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#3392 — toMethod should create a function without a prototype property