Formalize value pairs.

index.bs

@@ -3990,8 +3990,15 @@ If a single type parameter is given, then the interface has a
 values of the specified type.
 If two type parameters are given, then the interface has a
 <dfn id="dfn-pair-iterator" export>pair iterator</dfn> and provides
-value pairs, where the first value is a key and the second is the
-value associated with the key.
+[=value pairs=] with the given types.
+
+A <dfn>value pair</dfn>, given a key type and a value type, is a [=/struct=] with two
+[=struct/items=]:
+1.  an [=struct/item=] whose [=struct/name=] is "key", which is referred to as the [=value pair=]'s
+    <dfn for="value pair">key</dfn>, and whose value is an IDL value of the key type;
+1.  an [=struct/item=] whose [=struct/name=] is "value", which is referred to as the
+    [=value pair=]'s <dfn for="value pair">value</dfn>, and whose value is an IDL value of the
+    value type.
 
 A [=value iterator=]
 must only be declared on an interface
@@ -4005,11 +4012,10 @@ defined to iterate over the object’s indexed properties.
 A [=pair iterator=]
 must not be declared on an interface
 that [=support indexed properties|supports indexed properties=].
-Prose accompanying an interface with a
-[=pair iterator=]
-must define what the list of
-<dfn id="dfn-value-pairs-to-iterate-over" export>value pairs to iterate over</dfn>
-is.
+
+Prose accompanying an [=interface=] with a [=pair iterator=] must define a [=/list=] of
+[=value pairs=] for each instance of the [=interface=], which is the list of
+<dfn id="dfn-value-pairs-to-iterate-over" export>value pairs to iterate over</dfn>.
 
 <div class="note">
 
@@ -4070,8 +4076,9 @@ that have [=members=] with these names.
 
     <blockquote>
 
-        The [=value pairs to iterate over=] are the list of key-value pairs with the key being the username and the
-        value being the open <code class="idl">Session</code> object on the <code class="idl">SessionManager</code>
+        The [=value pairs to iterate over=] are the list of [=value pairs=] with the
+        [=value pair/key=] being the username and the [=value pair/value=] being the open
+        <code class="idl">Session</code> object on the <code class="idl">SessionManager</code>
         object corresponding to that username, sorted by username.
 
     </blockquote>
@@ -11576,8 +11583,8 @@ then the [=function object=] is {{%ArrayProto_forEach%}}.
     1.  Let |i| be 0.
     1.  While |i| is less than the length of |pairs|:
         1.  Let |pair| be the entry in |pairs| at index |i|.
-        1.  Let |key| be |pair|’s key.
-        1.  Let |value| be |pair|’s value.
+        1.  Let |key| be |pair|’s [=value pair/key=].
+        1.  Let |value| be |pair|’s [=value pair/value=].
         1.  [=Invoke=] |callback| with |thisArg|
             (or <emu-val>undefined</emu-val>, if the argument was not supplied)
             as the [=callback this value=] and |value|, |key| and <b>this</b> as its arguments.
@@ -11784,22 +11791,22 @@ The \[[Prototype]] [=internal slot=] of an [=iterator prototype object=]
 must be {{%IteratorPrototype%}}.
 
 <div algorithm>
-  The <dfn>iterator result</dfn> for a pair of IDL values |pair| and a kind |kind| is given by the
+  The <dfn>iterator result</dfn> for a [=value pair=] |pair| and a kind |kind| is given by the
   following steps:
 
     1.  Let |result| be a value determined by the value of |kind|:
         <dl class="switch">
              :  "<code>key</code>"
-             :: 1.  Let |idlKey| be |pair|’s key.
+             :: 1.  Let |idlKey| be |pair|’s [=value pair/key=].
                 1.  Let |key| be the result of [=converted to an ECMAScript value|converting=] |idlKey| to an ECMAScript value.
                 1.  |result| is |key|.
              :  "<code>value</code>"
-             :: 1.  Let |idlValue| be |pair|’s value.
+             :: 1.  Let |idlValue| be |pair|’s [=value pair/value=].
                 1.  Let |value| be the result of [=converted to an ECMAScript value|converting=] |idlValue| to an ECMAScript value.
                 1.  |result| is |value|.
              :  "<code>key+value</code>"
-             :: 1.  Let |idlKey| be |pair|’s key.
-                1.  Let |idlValue| be |pair|’s value.
+             :: 1.  Let |idlKey| be |pair|’s [=value pair/key=].
+                1.  Let |idlValue| be |pair|’s [=value pair/value=].
                 1.  Let |key| be the result of [=converted to an ECMAScript value|converting=] |idlKey| to an ECMAScript value.
                 1.  Let |value| be the result of [=converted to an ECMAScript value|converting=] |idlValue| to an ECMAScript value.
                 1.  Let |array| be the result of performing [$ArrayCreate$](2).