[css-conditional-4] Clarify that unknown/invalid portions of a selector that do not invalidate the selector cause the selector to be unsupported nonetheless. w3c#7280

Author: fantasai

css-conditional-4/Overview.bs

@@ -124,11 +124,16 @@ Extensions to the definition of support</h3>
 
 	A CSS processor is considered to
 	<dfn export for=CSS id="dfn-support-selector">support a CSS selector</dfn>
-	if it accepts that selector
-	(rather than discarding it as a parse error),
+	if it accepts that all aspects of that selector, recursively,
+	(rather than considering any of its syntax to be unknown or invalid)
 	and that selector doesn't contain
 	<a>unknown -webkit- pseudo-elements</a>.
 
+	Note: Some functional selectors are parsed forgivingly,
+	i.e. if some arguments are unknown/invalid,
+	the selector itself is not invalidated.
+	These are nonetheless unsupported
+
 <h2 class=no-num id="security">Security Considerations</h2>
 
 	No Security issues have been raised against this document
@@ -159,6 +164,14 @@ Extensions to the definition of support</h3>
 <h2 id='changes' class='no-num'>
 Changes</h2>
 
+<h3 id="changes-from-2022-02-17" class="no-num">
+Changes since the <a href="https://www.w3.org/TR/2022/CR-css-conditional-4-20220217/">Candidate Recommendation Snapshot of 17 February 2022</a></h3>
+
+	<ul>
+		<li>Clarify that unknown or invalid portions of a selector that do not invalidate the selector
+			nonetheless cause the selector to be considered unsupported.
+	</ul>
+
 <h3 id="changes-from-20200303" class="no-num">
 Changes since the <a href="https://www.w3.org/TR/2020/WD-css-conditional-4-20200303/">First Public Working Draft of 3 March 2020</a></h3>