On Jul 2, 2009, at 10:29 AM, Mark S. Miller wrote:
On Thu, Jul 2, 2009 at 9:26 AM, Allen Wirfs-Brock <[email protected]
> wrote:
Because built-in constructors are not (necessarily) implemented in
ECMAScript code they are not required to use the definitions of
[[Call]] and [[Construct]] given in 13.2.2 and 13.2.3. Arguably the
"Constructor Called as a Function" and "called as part of a new
expression" sections of chapter 15 are specifying the behavior of
custom [[Call]] and [[Construct]] internal methods for each built-in
constructor.
The problem is that .call(), .apply(), and .bind() are specified in
terms of [[Call]], so unless the connection is somehow made, it
technically becomes unspecified how native constructors respond to
these reflective operations.
AFAIK, the observed behavior across browsers is consistent with the
theory that "called as a function" actually documents the
constructor's [[Call]] method.
I'll see if can find a way to clarify this in the introduction to
chapter 15.
Some introductory text there would be adequate. No need to propagate
local changes.
In my initial message, I was also confused about whether "called as
a function" was meant to cover cases such as
foo.Error(x, y)
which I normally distinguish by saying "called as a method". If this
is not unclear in the context of the rest of the ES5 spec language,
no further explanatory note is needed, but may be helpful to readers
as confused as I.
In ECMAScript terms, what we informally call a "method call" is a kind
of function call that explicitly specifies the "this" object to use
for the call. So it's pretty clear to me that in the case of
foo.Error(x, y), Error is being called as a function.
Regards,
Maciej
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