Make call/construct/invoke either return an IDL value or throw

Their logic was relying too heavily on an implicit conversion between JS completion values and returning/throwing, which was especially confusing when we also had to deal with conversions between JS and IDL values.

Author: jyasskin

index.bs

@@ -14188,12 +14188,12 @@ the special value “missing”, which represents a missing optional argument.
         |callResult|.\[[Value]] to an IDL value of the same type as the operation's
         return type.
     1.  <i id="call-user-object-operation-return">Return:</i> at this
-        point |completion| will be set to an ECMAScript completion value.
+        point |completion| will be set to an IDL value or an [=abrupt completion=].
         1.  [=Clean up after running a callback=] with |stored settings|.
         1.  [=Clean up after running script=] with |relevant settings|.
-        1.  If |completion| is a normal completion, return |completion|.
+        1.  If |completion| is an IDL value, return |completion|.
         1.  If |completion| is an [=abrupt completion=] and the operation has a [=return type=]
-            that is <em>not</em> a [=promise type=], return |completion|.
+            that is <em>not</em> a [=promise type=], throw |completion|.\[[Value]].
         1.  Let |rejectedPromise| be [=!=] <a abstract-op>Call</a>({{%Promise.reject%}},
             {{%Promise%}}, «|completion|.\[[Value]]»).
         1.  Return the result of [=converted to an IDL value|converting=]
@@ -14276,12 +14276,12 @@ described in the previous section).
         |callResult|.\[[Value]] to an IDL value of the same type as the operation's
         return type.
     1.  <i id="invoke-return">Return:</i> at this
-        point |completion| will be set to an ECMAScript completion value.
+        point |completion| will be set to an IDL value or an [=abrupt completion=].
         1.  [=Clean up after running a callback=] with |stored settings|.
         1.  [=Clean up after running script=] with |relevant settings|.
-        1.  If |completion| is a normal completion, return |completion|.
+        1.  If |completion| is an IDL value, return |completion|.
         1.  If |completion| is an [=abrupt completion=] and the callback function has a
-            [=return type=] that is <em>not</em> a [=promise type=], return |completion|.
+            [=return type=] that is <em>not</em> a [=promise type=], throw |completion|.\[[Value]].
         1.  Let |rejectedPromise| be [=!=] <a abstract-op>Call</a>({{%Promise.reject%}},
             {{%Promise%}}, «|completion|.\[[Value]]»).
         1.  Return the result of [=converted to an IDL value|converting=]
@@ -14318,9 +14318,10 @@ a return type that is a [=promise type=].
         |callResult|.\[[Value]] to an IDL value of the same type as the operation's
         return type.
     1.  <i id="construct-return">Return:</i> at this
-        point |completion| will be set to an ECMAScript completion value.
+        point |completion| will be set to an IDL value or an [=abrupt completion=].
         1.  [=Clean up after running a callback=] with |stored settings|.
         1.  [=Clean up after running script=] with |relevant settings|.
+        1.  If |completion| is an [=abrupt completion=], throw |completion|.\[[Value]].
         1.  Return |completion|.
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