From 9da6deb4c7a1893c5f524991e7beef1d7a3ef692 Mon Sep 17 00:00:00 2001
From: Darren Shen <shend@chromium.org>
Date: Thu, 1 Feb 2018 13:16:15 +1100
Subject: [PATCH] Extend match concept to other style values

---
 css-typed-om/Overview.bs | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/css-typed-om/Overview.bs b/css-typed-om/Overview.bs
index 3ffff4eb..1ec4ab8f 100644
--- a/css-typed-om/Overview.bs
+++ b/css-typed-om/Overview.bs
@@ -355,7 +355,7 @@ probably in an appendix.
     and a [=string=] or {{CSSStyleValue}} |value|:
 
     : If |value| is a {{CSSStyleValue}},
-    :: If |value| does not match the grammar of a [=list-valued property iteration=] of |property|,
+    :: If |value| does not [=match a CSS production|match the grammar=] of a [=list-valued property iteration=] of |property|,
         [=throw=] a {{TypeError}} and exit this algorithm.
         Otherwise, return the |value|.
 
@@ -366,6 +366,18 @@ probably in an appendix.
         Note: This can throw a {{TypeError}} instead.
 </div>
 
+<div algorithm>
+    A {{CSSStyleValue}} is said to <dfn>match a CSS production</dfn>
+    based on the following rules:
+
+    * A {{CSSKeywordValue}} always matches <<ident>>.
+    * A {{CSSTransformValue}} always matches <<transform>>.
+    * A {{CSSPositionValue}} always matches <<position>>.
+    * A {{CSSNumericValue}} matches what its type [=CSSNumericValue/matches=].
+    * A {{CSSURLImageValue}} always matches <<url>>.
+    * Any subclass of {{CSSImageValue}} always matches <<image>>.
+</div>
+
 <div algorithm>
     The <dfn method for="StylePropertyMapReadOnly, StylePropertyMap">get(|property|)</dfn> method,
     when called on a {{StylePropertyMap}} |this|,