Re: [heycam/webidl] Import the Promises Guide. (#772)

Ms2ger commented on this pull request.



>  
 <div id="es-to-promise" algorithm="convert an ECMAScript value to promise">
 
     An ECMAScript value |V| is [=converted to an IDL value|converted=]
-    to an IDL <a interface lt="Promise">Promise<var ignore>T</var></a> value as follows:
+    to an IDL <code>{{Promise}}&lt;<var ignore>T</var>></code> value as follows:

Bah.

>          1.  Let |reason| be the result of [=converted to an IDL value|converting=]
             |R| to an IDL value of type {{any}}.
         1.  If there are no steps that are required to be run if the promise was rejected, then
             return <emu-val>undefined</emu-val>.
-        1.  Otherwise, return the result of performing any steps that were required to be run if the promise was rejected,
-            with |reason| as the rejection reason.
-    1.  Return [=!=] [$PerformPromiseThen$](|promise|, |onFulfilled|, |onRejected|).
+        1.  Let |result| be the result of performing any steps that were required to be run if the
+            promise was rejected, given |reason|.
+        1.  Return |result|, [=converted to an ECMAScript value=].
+    1.  Let |onRejected| be [=!=] [$CreateBuiltinFunction$](|onRejectedSteps|, « »):
+    1.  Let |constructor| be |promise|.\[[Promise]].\[[Realm]].\[[Intrinsics]].[[{{%Promise%}}]].
+    1.  Let |newCapability| be ? [$NewPromiseCapability$](|constructor|).
+    1.  Return [=!=] [$PerformPromiseThen$](|promise|.\[[Promise]], |onFulfilled|, |onRejected|, |newCapability|).
+
+    Note: If the provided steps return a value of type |T|, this algorithm returns a
+    <code>{{Promise}}&lt;<var ignore>T</var>&gt;</code>.

Yeah, definitely not T. Tried to clarify a bit.

> +    <pre highlight="webidl">
+        interface I {
+          Promise&lt;void> delay(unrestricted double ms);
+        };
+    </pre>
+
+<div algorithm="delay">
+
+    The <code>delay(|ms|)</code> method steps are:
+
+    1.  Let |realm| be <b>this</b>'s [=relevant Realm=].
+    1.  If |ms| is NaN, let |ms| be +0; otherwise let |ms| be the maximum of |ms| and +0.
+    1.  Let |p| be [=Promise/a new promise=] in |realm|.
+    1.  Run the following steps [=in parallel=]:
+        1.  Wait |ms| milliseconds.
+        1.  [=Promise/Resolve=] |p| with the {{void}} value.

Could be, yes. I'm not entirely sure how to phrase that, though.

>          1.  Let |R| be the first argument to |onRejected|.
         1.  Let |reason| be the result of [=converted to an IDL value|converting=]
             |R| to an IDL value of type {{any}}.
         1.  If there are no steps that are required to be run if the promise was rejected, then
             return <emu-val>undefined</emu-val>.
         1.  Otherwise, return the result of performing any steps that were required to be run if the promise was rejected,
             with |reason| as the rejection reason.
-    1.  Return [=!=] [$PerformPromiseThen$](|promise|, |onFulfilled|, |onRejected|).
+    1.  Let |onRejected| be [=!=] [$CreateBuiltinFunction$](|onRejectedSteps|, « »):
+    1.  Let |constructor| be |promise|.\[[Promise]].\[[Realm]].\[[Intrinsics]].[[{{%Promise%}}]].
+    1.  Let |newCapability| be ? [$NewPromiseCapability$](|constructor|).
+    1.  Return [=!=] [$PerformPromiseThen$](|promise|.\[[Promise]], |onFulfilled|, |onRejected|, |newCapability|).

Right, I meant to call that out explicitly, but it seems I forgot. I could add a note that it's not necessary to create the PromiseCapability 

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