Re: [heycam/webidl] Define "implements" checks using internal slots (#595)

littledan commented on this pull request.



> @@ -12337,18 +12336,73 @@ The value of the [=function object=]’s <code class="idl">name</code> property
 
 <h3 id="es-platform-objects">Platform objects implementing interfaces</h3>
 
+<div algorithm>
+    An ECMAScript value |value| <dfn id="es-is-platform-object">is a platform object</dfn>
+    if [$Type$](|value|) is Object and if |value| has a \[[PrimaryInterface]] internal slot.
+</div>
+
+<div algorithm>
+    An ECMAScript value |value| <dfn export>implements</dfn> an [=interface=] |interface|
+    if |value| [=is a platform object=] and one of the following is true:
+    <ul>
+        <li>|value|.\[[PrimaryInterface]] is |interface|.</li>
+        <li>The set of [=inherited interfaces=] of |value|.\[[PrimaryInterface]] contains |interface|.</li>

To clarify, what I like about this form of specification is that it makes it clear that, even when an object is in a deoptimized hashtable mode, no more than constant space is needed to represent the set of platform brands needed for a particular instance.

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