Re: [heycam/webidl] Add an algorithm to create a platform object. (#635)

Ms2ger commented on this pull request.



> @@ -12349,12 +12363,60 @@ It is the responsibility of specifications using Web IDL to state
 which global environment (or, by proxy, which global object) each platform
 object is associated with.
 
+<div algorithm>
+  To <dfn export lt="new|create|create a new|create an object implementing|create an object
+  implementing the interface">create an object implementing the interface</dfn> |interface| in the
+  Realm |realm|, with optional `new.target` value |newTarget|, perform the following steps:
+
+    1.  Assert: |interface| is [=exposed=] in |realm|.
+    1.  Let prototype be the [=interface prototype object=] for |interface| in
+        |realm|.
+    1.  If |newTarget| is provided, then:
+        1.  Issue: If we just pass {{NewTarget}} through in a constructor, would this not
+            always be defined (sometimes to the [=interface object=] itself)?

That would have some extremely surprising effects if interpreted to the letter. Consider the [`Response` constructor](https://fetch.spec.whatwg.org/#dom-response):

3. Let _r_ be a new `Response` object associated with a new response.
4. Set _r_’s headers to a new `Headers` object, whose header list is _r_’s response’s header list, and guard is "response".

If you just pull the NewTarget from the air, it would be used for both the `Response` and `Headers` objects.


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