[@scope] Allow declarations directly within @scope (#11161)

Author: andruud

css-cascade-6/Overview.bs

@@ -438,7 +438,7 @@ Syntax of ''@scope''</h4>
 
 	<pre class="prod def">
 	@scope [(<<scope-start>>)]? [to (<<scope-end>>)]? {
-	  <<rule-list>>
+	  <<block-contents>>
 	}
 	</pre>
 
@@ -448,7 +448,10 @@ Syntax of ''@scope''</h4>
 		used to identify the [=scoping root=](s).
 	* <dfn><<scope-end>></dfn> is a <<selector-list>> [=selector=]
 		used to identify any [=scoping limits=].
-	* the <<rule-list>> represents the [=scoped style rules=].
+	* the [=qualified rules=] within <<block-contents>>,
+		as well as any [=nested declarations rules=]
+		produced by [[#scoped-declarations|scoped declarations]],
+		represents the [=scoped style rules=].
 
 	[=Pseudo-elements=] cannot be [=scoping roots=] or [=scoping limits=];
 	they are invalid both within <<scope-start>> and <<scope-end>>.
@@ -667,6 +670,39 @@ Issue(10795): Should the scope proximity calculation be impacted by nesting scop
 	(e.g. within ''@layer'')
 	are [=scoped style rules|scoped=].
 
+<h4 id="scoped-declarations">
+Scoped Declarations </h4>
+
+	[=Declarations=] may be used directly
+	with the body of a ''@scope'' rule.
+	Contiguous runs of [=declarations=]
+	are wrapped in [=nested declarations rules=],
+	which match the [=scoping root=]
+	with zero [=specificity=].
+
+	<div class=example>
+		<pre highlight=css>
+		@scope (.foo) {
+		  border: 1px solid black;
+		}
+		</pre>
+
+		is equivalent to:
+
+		<pre highlight=css>
+		@scope (.foo) {
+		  :where(:scope) {
+		    border: 1px solid black;
+		  }
+		}
+		</pre>
+	</div>
+
+	Just like for [=style rules=],
+	[=declarations=] and child [=rules=]
+	may be [[css-nesting-1#mixing|mixed]]
+	within ''@scope''.
+
 <h3 id="preshint">
 Precedence of Non-CSS Presentational Hints</h3>
 
@@ -734,6 +770,9 @@ Changes since the 21 March 2023 Working Draft</h3>
 	Significant changes since the
 	<a href="https://www.w3.org/TR/2023/WD-css-cascade-6-20230321/">21 March 2023 Working Draft</a> include:
 
+	* Allowed [=declarations=] directly within ''@scope''.
+		(<a href="https://github.com/w3c/csswg-drafts/issues/10389">Issue 10389</a>)
+
 	* The '':scope'' selector can match the [=featureless=] [=shadow host=] when
 		that host is the [=scoping root=] element.
 		(<a href="https://github.com/w3c/csswg-drafts/issues/9025">Issue 9025</a>)