Normative: Add undefined-like exotic objects (aka document.all)

spec.html

@@ -3176,7 +3176,7 @@ <h1>ToBoolean ( _argument_ )</h1>
               Object
             </td>
             <td>
-              Return *true*.
+              Return *false* if _argument_ is an undefined-like exotic object; otherwise return *true*.
             </td>
           </tr>
           </tbody>
@@ -4074,6 +4074,8 @@ <h1>Abstract Equality Comparison</h1>
           1. Return the result of performing Strict Equality Comparison _x_ === _y_.
         1. If _x_ is *null* and _y_ is *undefined*, return *true*.
         1. If _x_ is *undefined* and _y_ is *null*, return *true*.
+        1. If _x_ is an undefined-like exotic object and _y_ *null*, *undefined*, or an undefined-like exotic object, return *true*.
+        1. If _x_ is *null* or *undefined* and _y_ is an undefined-like exotic object, return *true*.
         1. If Type(_x_) is Number and Type(_y_) is String, return the result of the comparison _x_ == ToNumber(_y_).
         1. If Type(_x_) is String and Type(_y_) is Number, return the result of the comparison ToNumber(_x_) == _y_.
         1. If Type(_x_) is Boolean, return the result of the comparison ToNumber(_x_) == _y_.
@@ -8159,6 +8161,14 @@ <h1>[[SetPrototypeOf]] (_V_)</h1>
         </emu-alg>
       </emu-clause>
     </emu-clause>
+
+    <emu-clause id="sec-undefined-like-exotic-objects">
+      <h1>Undefined-like Exotic Objects</h1>
+      <p>An <dfn>undefined-like exotic object</dfn> is an exotic object that behaves like undefined in the <emu-xref href="#sec-toboolean">ToBoolean</emu-xref> and <emu-xref href="#sec-abstract-equality-comparison">Abstract Equality Comparison</emu-xref> abstract operations and when used as an operand for the <emu-xref href="#sec-typeof-operator">typeof operator</emu-xref>. Undefined-like exotic objects have all the ordinary object internal methods and slots.</p>
+      <emu-note>
+        <p>Undefined-like exotic objects are never created by this specification. However, the <a href="https://html.spec.whatwg.org/multipage/obsolete.html#dom-document-all">document.all object</a> in web browsers is a host-created undefined-like exotic object that exists for web compatibility purposes. There are no other known examples of this type of object.</p>
+      </emu-note>
+    </emu-clause>
   </emu-clause>
 
   <!-- es6num="9.5" -->
@@ -12472,6 +12482,14 @@ <h1>Runtime Semantics: Evaluation</h1>
                 Implementation-defined. Must not be `"undefined"`, `"boolean"`, `"function"`, `"number"`, `"symbol"`, or `"string"`.
               </td>
             </tr>
+            <tr>
+              <td>
+                Object (undefined-like exotic object)
+              </td>
+              <td>
+                `"undefined"`
+              </td>
+            </tr>
             </tbody>
           </table>
         </emu-table>