Brendan Eich wrote:
Irakli Gozalishvili wrote:
It would be amazing to have clojure like protocols in JS even
without `IFn`. I think it's very good feet and very useful in JS
where each library has it's own flavored API. I wrote more about it
here:
http://jeditoolkit.com/2012/03/21/protocol-based-polymorphism.html#post
Still hoping Mark will weigh in.
Ok, I talked to Mark and Tom Van Cutsem, and they see no problem
provided we prevent overriding built-in [[Call]] and [[Construct]] on
function objects.
Let there be private names @call and @construct (I'll spell them this
way to avoid tedious imports of const bindings from "@std" or another
built-in module).
Let Clause 15.3.5 include new non-configurable, non-writable properties
of function objects named by @call and @construct (built-in functions
have only @call). The values are built-in and need a bit more thought
than I can spare now, but see below: @call's value is close to the
original value of Function.prototype.call, and @construct's value is
straightforward enough I think.
Change 11.2.2 "The new Operator" to use @construct not [[Construct]],
passing the /argList// spread as actual positional parameters: (...argList).
Change 11.2.3 "Function Calls" to use @call not [[Call]], passing the
/thisValue/ and /argList/ according to the Function.prototype.call
convention: (thisValue, ...argList).
Change 11.4.3 "The typeof Operator", the table row with "Object (native
or host and does implement [[Call]])" in column 1, to test not for
[[Call]] and *not* for @call, rather to test [[NativeBrand]] ===
"Function" (see ES6 draft 15.2.4.2 "Object.prototype.toString ( )").
This last point is important: we do not want an object's typeof-type to
change by giving it a @call property. But we do want to enable call and
construct protocols to be built by users, by giving objects @call and
@construct properties.
This also simplifies direct proxies by allowing any proxy to have call
and construct traps.
Comments welcome.
/be
_______________________________________________
es-discuss mailing list
[email protected]
https://mail.mozilla.org/listinfo/es-discuss
