From 9f6d66989ab42d1551f0384be42898b4c3120798 Mon Sep 17 00:00:00 2001 From: Daniel Ehrenberg Date: Tue, 30 Oct 2018 15:52:41 +0100 Subject: [PATCH 1/7] Normative: Add `kind: "initializer"` for side effects Many decorators will want to perform a side effect when instantiating a class, for example: - To select [[Set]] rather than [[DefineOwnProperty]] semantics for defining a field - To store the field in an entirely different place, neither an ordinary property or private field (e.g., MobX stores some fields in a Map) - To register the instance under construction in some way (e.g., from a class decorator). "Instance finishers" have been proposed for this purpose, but it's not clear when to run such a finisher. For many use cases (e.g., interacting with the DOM), an instance "starter" is just as good, due to run-to-completion semantics. This patch permits decorators to create elements of the form { kind: "initializer", placement: "own", initializer: fn } to be used purely for their side effect, with evaluation semantics and ordering identical to fields, and interspersed with them in evaluation order. --- spec.html | 69 +++++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 57 insertions(+), 12 deletions(-) diff --git a/spec.html b/spec.html index e7ff9de..0f85a41 100644 --- a/spec.html +++ b/spec.html @@ -159,7 +159,7 @@

The ElementDescriptor Specification Type

Field Name Value - [[Kind]] One of `"method"` or `"field"` + [[Kind]] One of `"method"`, `"field"` or `"initializer"` [[Key]] A Property Key or %PrivateName% object [[Descriptor]] A Property Descriptor [[Placement]] One of `"static"`, `"prototype"`, or `"own"` @@ -188,6 +188,16 @@

The ElementDescriptor Specification Type

  • _element_.[[Descriptor]].[[Configurable]] is *false*.
    • +
  • + If _element_.[[Kind]] is `"initializer", then + +

    • @@ -408,6 +418,27 @@

    CoalesceClassElements ( _elements_ )

    In the case of public class elements, coalescing corresponds in semantics to ValidateAndApplyPropertyDescriptor. Note that this algorithm only coalesces method and accessor declarations, and it leaves field declarations as is. + +

    InitializeInstanceElements ( _O_, _constructor_ )

    + + + 1. Assert: Type ( _O_ ) is Object. + 1. Assert: Assert _constructor_ is an ECMAScript function object. + 1. Let _elements_ be the value of _F_'s [[Elements]] internal slot. + 1. For each item _element_ in order from _elements_, + 1. If _element_.[[Placement]] is `"own"` and _element_.[[Kind]] is `"method"`, + 1. Perform ? DefineClassElement(_O_, _element_). + 1. For each item _element_ in order from _elements_, + 1. If _element_.[[Placement]] is `"own"` and _element_.[[Kind]] is `"field"`, + 1. Assert: _element_.[[Descriptor]] does not have a [[Value]], [[Get]] or [[Set]] slot. + 1. Perform ? DefineClassElement(_O_, _element_). + 1. If _element_.[[Kind]] is `"initializer"`, + 1. Assert: _element_.[[Placement]] is `"own"`. + 1. Perform ? Call(_element_.[[Initializer]], _O_). + 1. Return. + +     + @@ -563,7 +594,7 @@

    Element Descriptors

    An element descriptor describes an element of a class or object literal and has the following shape:

    
         interface ElementDescriptor {
-          kind: "method" or "field"
+          kind: "method", "initializer" or "field"
           key: String, Symbol or Private Name,
           placement: "static", "prototype", or "own"
           descriptor: PropertyDescriptor,
@@ -689,7 +720,7 @@ 
    DecorateConstructor ( _elements_, _decorators_ )
    
             1. Append _elementsAndFinisher_.[[Finisher]] to _finishers_.
           1. If _elementsAndFinisher_.[[Elements]] is not *undefined*,
             1. Set _elements_ to the concatenation of _elementsAndFinisher_.[[Elements]] and _privateElements_.
-            1. If there are two class elements _a_ and _b_ in _elements_ such that _a_.[[Key]] is _b_.[[Key]] and _a_.[[Placement]] is _b_.[[Placement]], throw a *TypeError* exception.
+            1. If there are two class elements _a_ and _b_ in _elements_ such that _a_.[[Kind]] is not `"initializer"` and _b_.[[Kind]] is not `"initializer"`, _a_.[[Key]] is _b_.[[Key]], and _a_.[[Placement]] is _b_.[[Placement]], throw a *TypeError* exception.
         1. Return the Record { [[Elements]]: _elements_, [[Finishers]]: _finishers_ }.
       
     
@@ -744,12 +775,14 @@ 
    FromElementDescriptor ( _element_ )
    
         1. Let _desc_ be PropertyDescriptor{ [[Value]]: `"Descriptor"`, [[Writable]]: *false*, [[Enumerable]]: *false*, [[Configurable]]: *true* }.
         1. Perform ! DefinePropertyOrThrow(_obj_, @@toStringTag, _desc_).
         1. Perform ! CreateDataPropertyOrThrow(_obj_, `"kind"`, _element_.[[Kind]]).
-        1. Let _key_ be _element_.[[Key]].
-        1. If _key_ is a Private Name, set _key_ to ? PrivateNameObject(_key_).
-        1. Perform ! CreateDataPropertyOrThrow(_obj_, `"key"`, _key_).
+        1. If _element_.[[Kind]] is `"method"` or `"field"`,
+          1. Let _key_ be _element_.[[Key]].
+          1. If _key_ is a Private Name, set _key_ to ? PrivateNameObject(_key_).
+          1. Perform ! CreateDataPropertyOrThrow(_obj_, `"key"`, _key_).
         1. Perform ! CreateDataPropertyOrThrow(_obj_, `"placement"`, _element_.[[Placement]]).
-        1. Perform ! CreateDataPropertyOrThrow(_obj_, `"descriptor"`, ! FromPropertyDescriptor(_element_.[[Descriptor]])).
-        1. If _element_.[[Kind]] is `"field"`,
+        1. If _element_.[[Kind]] is `"method"` or `"field"`,
+          1. Perform ! CreateDataPropertyOrThrow(_obj_, `"descriptor"`, ! FromPropertyDescriptor(_element_.[[Descriptor]])).
+        1. If _element_.[[Kind]] is `"field"` or `"initializer"`,
           1. Let _initializer_ be _element_.[[Initializer]].
           1. If _initializer_ is ~empty~, set _initializer_ to *undefined*.
           1. Perform ! CreateDataPropertyOrThrow(_obj_, `"initializer"`, _initializer_).
@@ -784,14 +817,22 @@ 
    ToElementDescriptor ( _elementObject_ )
    
         1. If _kind_ is not one of `"method"` or `"field"`, throw a *TypeError* exception.
         1. Let _key_ be ? Get(_elementObject_, `"key"`).
         1. If _key_ has a [[PrivateName]] internal slot, set _key_ to _key_.[[PrivateName]].
+        1. If _kind_ is `"initializer"`,
+          1. If _key_ is not *undefined*, throw a *TypeError* exception.
         1. Otherwise, set _key_ to ? ToPropertyKey(_key_).
         1. Let _placement_ be ? ToString(? Get(_elementObject_, `"placement"`)).
         1. If _placement_ is not one of `"static"`, `"prototype"`, or `"own"`, throw a *TypeError* exception.
-        1. Let _descriptor_ be ? ToPropertyDescriptor(? Get(_elementObject_, `"descriptor"`)).
+        1. If _kind_ is `"initializer"`,
+          1. If _placement_ is not `"own"`, throw a *TypeError* exception.
+        1. Let _descriptor_ be ? Get(_elementObject_, `"descriptor"`)
+        1. If _kind_ is `"initializer"`,
+          1. If _descriptor_ is not *undefined*, throw a *TypeError* exception.
+        1. Otherwise,
+          1. Set _descriptor_ to ? ToPropertyDescriptor(_descriptor_).
         1. Let _initializer_ be ? Get(_elementObject_, `"initializer"`).
         1. Let _elements_ be ? Get(_elementObject_, `"elements"`).
         1. If _elements_ is not *undefined*, throw a *TypeError* exception.
-        1. If _kind_ not `"field"`,
+        1. If _kind_ not `"field"` or `"initializer"`,
           1. If _initializer_ is not *undefined*, throw a *TypeError* exception.
         1. If _key_ is a Private Name,
           1. If _descriptor_.[[Enumerable]] is *true*, throw a *TypeError* exception.
@@ -799,8 +840,12 @@ 
    ToElementDescriptor ( _elementObject_ )
    
           1. If _placement_ is `"prototype"`, throw a *TypeError* exception.
         1. If _kind_ is `"field"`,
           1. If _descriptor_ has a [[Get]], [[Set]] or [[Value]] internal slot, throw a *TypeError* exception.
-        1. Let _element_ be the ElementDescriptor { [[Kind]]: _kind_, [[Key]]: _key_, [[Placement]]: _placement_, [[Descriptor]]: _descriptor_ }.
-        1. If _kind_ is `"field"`, set _element_.[[Initializer]] to _initializer_.
+        1. Let _element_ be the ElementDescriptor { [[Kind]]: _kind_, [[Placement]]: _placement_ }.
+        1. If _kind_ is `"method"` or `"field",
+           1. Set _element_.[[Key]] to _key_.
+           1. Set _element_.[[Descriptor]] to _descriptor_.
+        1. If _kind_ is `"field"` or `"initializer"`,
+           1. Set _element_.[[Initializer]] to _initializer_.
         1. Return _element_.
       
     

From 5bba880de0b52597e75f8788e14ba9ab9bd9acee Mon Sep 17 00:00:00 2001
From: Daniel Ehrenberg 
Date: Fri, 2 Nov 2018 21:15:03 +0100
Subject: [PATCH 2/7] Fix most of the errors from review

---
 spec.html | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/spec.html b/spec.html
index 0f85a41..bcba671 100644
--- a/spec.html
+++ b/spec.html
@@ -720,7 +720,12 @@ 
    DecorateConstructor ( _elements_, _decorators_ )
    
             1. Append _elementsAndFinisher_.[[Finisher]] to _finishers_.
           1. If _elementsAndFinisher_.[[Elements]] is not *undefined*,
             1. Set _elements_ to the concatenation of _elementsAndFinisher_.[[Elements]] and _privateElements_.
-            1. If there are two class elements _a_ and _b_ in _elements_ such that _a_.[[Kind]] is not `"initializer"` and _b_.[[Kind]] is not `"initializer"`, _a_.[[Key]] is _b_.[[Key]], and _a_.[[Placement]] is _b_.[[Placement]], throw a *TypeError* exception.
+            1. If there are two class elements _a_ and _b_ in _elements_ such that all of the following are true:
+              1. _a_.[[Kind]] is not `"initializer"`
+              1. _b_.[[Kind]] is not `"initializer"`
+              1. _a_.[[Key]] is _b_.[[Key]]
+              1. _a_.[[Placement]] is _b_.[[Placement]]
+            1. Then, throw a *TypeError* exception.
         1. Return the Record { [[Elements]]: _elements_, [[Finishers]]: _finishers_ }.
       
     
@@ -816,9 +821,9 @@ 
    ToElementDescriptor ( _elementObject_ )
    
         1. Let _kind_ be ? ToString(? Get(_elementObject_, `"kind"`)).
         1. If _kind_ is not one of `"method"` or `"field"`, throw a *TypeError* exception.
         1. Let _key_ be ? Get(_elementObject_, `"key"`).
-        1. If _key_ has a [[PrivateName]] internal slot, set _key_ to _key_.[[PrivateName]].
         1. If _kind_ is `"initializer"`,
           1. If _key_ is not *undefined*, throw a *TypeError* exception.
+        1. If _key_ has a [[PrivateName]] internal slot, set _key_ to _key_.[[PrivateName]].
         1. Otherwise, set _key_ to ? ToPropertyKey(_key_).
         1. Let _placement_ be ? ToString(? Get(_elementObject_, `"placement"`)).
         1. If _placement_ is not one of `"static"`, `"prototype"`, or `"own"`, throw a *TypeError* exception.
@@ -832,7 +837,7 @@ 
    ToElementDescriptor ( _elementObject_ )
    
         1. Let _initializer_ be ? Get(_elementObject_, `"initializer"`).
         1. Let _elements_ be ? Get(_elementObject_, `"elements"`).
         1. If _elements_ is not *undefined*, throw a *TypeError* exception.
-        1. If _kind_ not `"field"` or `"initializer"`,
+        1. If _kind_ is not `"field"` or `"initializer"`,
           1. If _initializer_ is not *undefined*, throw a *TypeError* exception.
         1. If _key_ is a Private Name,
           1. If _descriptor_.[[Enumerable]] is *true*, throw a *TypeError* exception.

From 14b8919936608de7919063371b0552b000cc0a37 Mon Sep 17 00:00:00 2001
From: Daniel Ehrenberg 
Date: Fri, 2 Nov 2018 22:29:05 +0100
Subject: [PATCH 3/7] Normative: Throw an exception on a missing initializer

---
 spec.html | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/spec.html b/spec.html
index bcba671..ddaead3 100644
--- a/spec.html
+++ b/spec.html
@@ -821,8 +821,6 @@ 
    ToElementDescriptor ( _elementObject_ )
    
         1. Let _kind_ be ? ToString(? Get(_elementObject_, `"kind"`)).
         1. If _kind_ is not one of `"method"` or `"field"`, throw a *TypeError* exception.
         1. Let _key_ be ? Get(_elementObject_, `"key"`).
-        1. If _kind_ is `"initializer"`,
-          1. If _key_ is not *undefined*, throw a *TypeError* exception.
         1. If _key_ has a [[PrivateName]] internal slot, set _key_ to _key_.[[PrivateName]].
         1. Otherwise, set _key_ to ? ToPropertyKey(_key_).
         1. Let _placement_ be ? ToString(? Get(_elementObject_, `"placement"`)).
@@ -835,7 +833,10 @@ 
    ToElementDescriptor ( _elementObject_ )
    
         1. Otherwise,
           1. Set _descriptor_ to ? ToPropertyDescriptor(_descriptor_).
         1. Let _initializer_ be ? Get(_elementObject_, `"initializer"`).
+        1. If _kind_ is `"initializer"` and _initializer_ is *undefined*, throw a *TypeError* exception
         1. Let _elements_ be ? Get(_elementObject_, `"elements"`).
+        1. If _kind_ is `"initializer"`,
+          1. If _key_ is not *undefined*, throw a *TypeError* exception.
         1. If _elements_ is not *undefined*, throw a *TypeError* exception.
         1. If _kind_ is not `"field"` or `"initializer"`,
           1. If _initializer_ is not *undefined*, throw a *TypeError* exception.

From 9c3c148018d7f2949736154e6bfc52d5bfcae646 Mon Sep 17 00:00:00 2001
From: Daniel Ehrenberg 
Date: Mon, 5 Nov 2018 00:06:45 +0100
Subject: [PATCH 4/7] Normative: Permit prototype and static initializers

Also move error checks in ToElementDescriptor to happen ASAP
---
 spec.html | 50 ++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 36 insertions(+), 14 deletions(-)

diff --git a/spec.html b/spec.html
index ddaead3..6687049 100644
--- a/spec.html
+++ b/spec.html
@@ -193,7 +193,6 @@ 
    The ElementDescriptor Specification Type
    
             
      
               
    • _element_.[[Key]] absent.
      • 
               
    • _element_.[[Descriptor]] is absent.
      • 
-              
    • _element_.[[Placement]] is `"own"`.
      • 
               
    • _element_.[[Initializer]] is present.
      • 
               
    • _element_.[[Decorators]] is absent.
      • 
             
    
@@ -432,13 +431,37 @@ 
    InitializeInstanceElements ( _O_, _constructor_ )
    
       1. If _element_.[[Placement]] is `"own"` and _element_.[[Kind]] is `"field"`,
         1. Assert: _element_.[[Descriptor]] does not have a [[Value]], [[Get]] or [[Set]] slot.
         1. Perform ? DefineClassElement(_O_, _element_).
-      1. If _element_.[[Kind]] is `"initializer"`,
-        1. Assert: _element_.[[Placement]] is `"own"`.
+      1. If _element_.[[Kind]] is `"initializer"` and _element_.[[Placement]] is `"own"`,
         1. Perform ? Call(_element_.[[Initializer]], _O_).
     1. Return.
   
 
 
+
+  
    InitializeClassElements(_F_, _proto_)
    
+
+  
+    1. Assert: Type(_F_) is Object and Type(_proto_) is Object.
+    1. Assert: _F_ is an ECMAScript function object.
+    1. Assert: _proto_ is ! Get(_F_, `"prototype"`).
+    1. Let _elements_ be the value of _F_'s [[Elements]] internal slot.
+    1. For each item _element_ in order from _elements_,
+      1. Assert: If _element_.[[Placement]] is `"prototype"` or `"static"`, then _element_.[[Key]] is not a Private Name.
+      1. If _element_.[[Kind]] is `"method"`,
+        1. Let _receiver_ be _F_ if _element_.[[Placement]] is `"static"`, else let _receiver_ be _proto_.
+        1. Perform ? DefineClassElement(_receiver_, _element_).
+    1. For each item _element_ in order from _elements_,
+      1. If _element_.[[Kind]] is `"field"` and _element_.[[Placement]] is `"static"` or `"prototype"`,
+        1. Assert: _element_.[[Descriptor]] does not have a [[Value]], [[Get]] or [[Set]] slot.
+        1. Let _receiver_ be _F_ if _element_.[[Placement]] is `"static"`, else let _receiver_ be _proto_.
+        1. Perform ? DefineClassElement(_receiver_, _element_).
+      1. If _element_.[[Placement]] is `"prototype"` or `"static"` and _element_.[[Kind]] is `"initializer"`,
+        1. Perform ? Call(_element_.[[Initializer]], _O_).
+    1. Return.
+  
+  Value properties are added before initializers so that all methods are visible from all initializers
+    
+
 
 
 
@@ -819,33 +842,32 @@ 
    ToElementDescriptor ( _elementObject_ )
    
       
         1. Assert: _elementObject_ is an ECMAScript language value.
         1. Let _kind_ be ? ToString(? Get(_elementObject_, `"kind"`)).
-        1. If _kind_ is not one of `"method"` or `"field"`, throw a *TypeError* exception.
+        1. If _kind_ is not one of `"initializer"`, `"method"` or `"field"`, throw a *TypeError* exception.
         1. Let _key_ be ? Get(_elementObject_, `"key"`).
+        1. If _kind_ is `"initializer"`,
+          1. If _key_ is not *undefined*, throw a *TypeError* exception.
         1. If _key_ has a [[PrivateName]] internal slot, set _key_ to _key_.[[PrivateName]].
         1. Otherwise, set _key_ to ? ToPropertyKey(_key_).
         1. Let _placement_ be ? ToString(? Get(_elementObject_, `"placement"`)).
         1. If _placement_ is not one of `"static"`, `"prototype"`, or `"own"`, throw a *TypeError* exception.
-        1. If _kind_ is `"initializer"`,
-          1. If _placement_ is not `"own"`, throw a *TypeError* exception.
         1. Let _descriptor_ be ? Get(_elementObject_, `"descriptor"`)
         1. If _kind_ is `"initializer"`,
           1. If _descriptor_ is not *undefined*, throw a *TypeError* exception.
         1. Otherwise,
           1. Set _descriptor_ to ? ToPropertyDescriptor(_descriptor_).
-        1. Let _initializer_ be ? Get(_elementObject_, `"initializer"`).
-        1. If _kind_ is `"initializer"` and _initializer_ is *undefined*, throw a *TypeError* exception
-        1. Let _elements_ be ? Get(_elementObject_, `"elements"`).
-        1. If _kind_ is `"initializer"`,
-          1. If _key_ is not *undefined*, throw a *TypeError* exception.
-        1. If _elements_ is not *undefined*, throw a *TypeError* exception.
-        1. If _kind_ is not `"field"` or `"initializer"`,
-          1. If _initializer_ is not *undefined*, throw a *TypeError* exception.
         1. If _key_ is a Private Name,
           1. If _descriptor_.[[Enumerable]] is *true*, throw a *TypeError* exception.
           1. If _descriptor_.[[Configurable]] is *true*, throw a *TypeError* exception.
           1. If _placement_ is `"prototype"`, throw a *TypeError* exception.
         1. If _kind_ is `"field"`,
           1. If _descriptor_ has a [[Get]], [[Set]] or [[Value]] internal slot, throw a *TypeError* exception.
+        1. Let _initializer_ be ? Get(_elementObject_, `"initializer"`).
+        1. If _kind_ is `"initializer"`,
+          1. If _initializer_ is *undefined*, throw a *TypeError* exception
+        1. If _kind_ is `"method"`,
+          1. If _initializer_ is not *undefined*, throw a *TypeError* exception.
+        1. Let _elements_ be ? Get(_elementObject_, `"elements"`).
+        1. If _elements_ is not *undefined*, throw a *TypeError* exception.
         1. Let _element_ be the ElementDescriptor { [[Kind]]: _kind_, [[Placement]]: _placement_ }.
         1. If _kind_ is `"method"` or `"field",
            1. Set _element_.[[Key]] to _key_.

From 77543ec38384e746b2d03b6447445549f9455866 Mon Sep 17 00:00:00 2001
From: Daniel Ehrenberg 
Date: Mon, 5 Nov 2018 11:00:25 +0100
Subject: [PATCH 5/7] Normative: Throw a TypeError if an initializer returns
 undefined

---
 spec.html | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/spec.html b/spec.html
index 6687049..07e2d7c 100644
--- a/spec.html
+++ b/spec.html
@@ -432,7 +432,8 @@ 
    InitializeInstanceElements ( _O_, _constructor_ )
    
         1. Assert: _element_.[[Descriptor]] does not have a [[Value]], [[Get]] or [[Set]] slot.
         1. Perform ? DefineClassElement(_O_, _element_).
       1. If _element_.[[Kind]] is `"initializer"` and _element_.[[Placement]] is `"own"`,
-        1. Perform ? Call(_element_.[[Initializer]], _O_).
+        1. Let _res_ be ? Call(_element_.[[Initializer]], _O_).
+        1. If _res_ is not *undefined*, throw a *TypeError* exception.
     1. Return.
       
 
@@ -456,7 +457,9 @@ 
    InitializeClassElements(_F_, _proto_)
    
         1. Let _receiver_ be _F_ if _element_.[[Placement]] is `"static"`, else let _receiver_ be _proto_.
         1. Perform ? DefineClassElement(_receiver_, _element_).
       1. If _element_.[[Placement]] is `"prototype"` or `"static"` and _element_.[[Kind]] is `"initializer"`,
-        1. Perform ? Call(_element_.[[Initializer]], _O_).
+        1. Let _receiver_ be _F_ if _element_.[[Placement]] is `"static"`, else let _receiver_ be _proto_.
+        1. Let _res_ be ? Call(_element_.[[Initializer]], _receiver_).
+        1. If _res_ is not *undefined*, throw a *TypeError* exception.
     1. Return.
   
   Value properties are added before initializers so that all methods are visible from all initializers

From 77e19228acdb149af03bdd34b85664079f3b8898 Mon Sep 17 00:00:00 2001
From: Daniel Ehrenberg 
Date: Mon, 5 Nov 2018 11:16:28 +0100
Subject: [PATCH 6/7] Documentation for initializers

---
 METAPROGRAMMING.md | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/METAPROGRAMMING.md b/METAPROGRAMMING.md
index 5a97220..0088851 100644
--- a/METAPROGRAMMING.md
+++ b/METAPROGRAMMING.md
@@ -138,6 +138,22 @@ A class descriptor with the following properties:
 
 Note: finishers run once per class (at class creation time), not once per instance.
 
+### Initializers
+
+The `extras` array can also contain stand-alone initializers, of the following form:
+
+```js
+{
+  kind: "initializer"
+  placement: "static", "prototype" or "own",
+  initializer() { /* ... */ }
+}
+```
+
+The initializers added here are just like field initializers, except that they don't result in defining a field.
+
+These can be used, e.g., to make a decorator which defines fields through `[[Set]]` rather than `[[DefineOwnProperty]]`, or to store the field in some other place.
+
 ## Examples
 
 The three decorators from [README.md](README.md) could be defined as follows:

From 9acf8f50bc9669e49bd1cf9849f59c71901c1532 Mon Sep 17 00:00:00 2001
From: Daniel Ehrenberg 
Date: Mon, 5 Nov 2018 11:21:48 +0100
Subject: [PATCH 7/7] Add Oxford commas

---
 spec.html | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/spec.html b/spec.html
index 07e2d7c..63b0586 100644
--- a/spec.html
+++ b/spec.html
@@ -620,7 +620,7 @@ 
    Element Descriptors
    
       
    An element descriptor describes an element of a class or object literal and has the following shape:
    
       
    
         interface ElementDescriptor {
-          kind: "method", "initializer" or "field"
+          kind: "method", "initializer", or "field"
           key: String, Symbol or Private Name,
           placement: "static", "prototype", or "own"
           descriptor: PropertyDescriptor,
@@ -845,7 +845,7 @@ 
    ToElementDescriptor ( _elementObject_ )
    
       
         1. Assert: _elementObject_ is an ECMAScript language value.
         1. Let _kind_ be ? ToString(? Get(_elementObject_, `"kind"`)).
-        1. If _kind_ is not one of `"initializer"`, `"method"` or `"field"`, throw a *TypeError* exception.
+        1. If _kind_ is not one of `"initializer"`, `"method"`, or `"field"`, throw a *TypeError* exception.
         1. Let _key_ be ? Get(_elementObject_, `"key"`).
         1. If _kind_ is `"initializer"`,
           1. If _key_ is not *undefined*, throw a *TypeError* exception.