rewrite funky setter and extract as an AO

spec.html

@@ -107,6 +107,30 @@ <h1>Well-Known Intrinsic Objects</h1>
 <emu-clause id="sec-abstract-operations">
   <h1>Abstract Operations</h1>
 
+  <emu-clause id="sec-SetterThatIgnoresPrototypeProperties" type="abstract operation">
+    <h1>
+      SetterThatIgnoresPrototypeProperties (
+        _home_: an Object,
+        _p_: a property key,
+        _v_: an ECMAScript language value,
+      ): either a normal completion containing ~unused~ or a throw completion
+    </h1>
+    <dl class="header">
+    </dl>
+    <emu-alg>
+      1. Let _O_ be ? RequireObjectCoercible(*this* value).
+      1. If _O_ is _home_, then
+        1. NOTE: Throwing here emulates assignment to a non-writable data property on the _home_ object in strict mode code.
+        1. Throw a *TypeError* exception.
+      1. Let _desc_ be ? _O_.[[GetOwnProperty]](_p_).
+      1. If _desc_ is *undefined*, then
+        1. Perform ? CreateDataPropertyOrThrow(_O_, _p_, _v_).
+      1. Else,
+        1. Perform ? Set(_O_, _p_, _v_, *true*).
+      1. Return ~unused~.
+    </emu-alg>
+  </emu-clause>
+
   <emu-clause id="sec-operations-on-iterator-objects">
     <h1>Operations on Iterator Objects</h1>
 
@@ -303,14 +327,7 @@ <h1>get Iterator.prototype.constructor</h1>
           <h1>set Iterator.prototype.constructor</h1>
           <p>The value of the [[Set]] attribute is a built-in function that takes an argument _v_. It performs the following steps when called:</p>
           <emu-alg>
-            1. Let _O_ be ? RequireObjectCoercible(*this* value).
-            1. If _O_ is %Iterator.prototype%, then
-              1. Throw a *TypeError* exception.
-            1. Let _desc_ be ? _O_.[[GetOwnProperty]](*"constructor"*).
-            1. If IsDataDescriptor(_desc_) is *true* and _desc_.[[Writable]] is *false*, then
-              1. Throw a *TypeError* exception.
-            1. Let _newDesc_ be the PropertyDescriptor { [[Value]]: _v_, [[Writable]]: *true*, [[Enumerable]]: *false*, [[Configurable]]: *true* }.
-            1. Perform ? _O_.[[DefineOwnProperty]](*"constructor"*, _newDesc_).
+            1. Perform ? SetterThatIgnoresPrototypeProperties(%Iterator.prototype%, *"constructor"*, _v_).
             1. Return *undefined*.
           </emu-alg>
         </emu-clause>
@@ -605,14 +622,7 @@ <h1>get Iterator.prototype [ @@toStringTag ]</h1>
           <h1>set Iterator.prototype [ @@toStringTag ]</h1>
           <p>The value of the [[Set]] attribute is a built-in function that takes an argument _v_. It performs the following steps when called:</p>
           <emu-alg>
-            1. Let _O_ be ? RequireObjectCoercible(*this* value).
-            1. If _O_ is %Iterator.prototype%, then
-              1. Throw a *TypeError* exception.
-            1. Let _desc_ be ? _O_.[[GetOwnProperty]](@@toStringTag).
-            1. If IsDataDescriptor(_desc_) is *true* and _desc_.[[Writable]] is *false*, then
-              1. Throw a *TypeError* exception.
-            1. Let _newDesc_ be the PropertyDescriptor { [[Value]]: _v_, [[Writable]]: *true*, [[Enumerable]]: *false*, [[Configurable]]: *true* }.
-            1. Perform ? _O_.[[DefineOwnProperty]](@@toStringTag, _newDesc_).
+            1. Perform ? SetterThatIgnoresPrototypeProperties(%Iterator.prototype%, %Symbol.toStringTag%, _v_).
             1. Return *undefined*.
           </emu-alg>
         </emu-clause>