[selectors-4] Limit :nth-child() etc. to compound selectors. #3760

Author: fantasai

selectors-4/Overview.bs

@@ -2834,7 +2834,7 @@ Child-indexed Pseudo-classes
 	are among An+Bth elements
 	from the list composed of
 	their inclusive siblings that match the selector list S,
-	which is [=parsed as a forgiving selector list=].
+	which is a <> [=parsed as a forgiving selector list=].
 	If S is omitted,
 	it defaults to ''*|*''.
 
@@ -2922,6 +2922,9 @@ Child-indexed Pseudo-classes
 		
 	
 
+	Note: We intend to extend '':nth-child()'' to accept <>
+	in Level 5.
+
 
 '':nth-last-child()'' pseudo-class
 
@@ -2931,7 +2934,7 @@ Child-indexed Pseudo-classes
 	from the list composed of
 	their inclusive siblings that match the selector list S,
 	counting backwards from the end.
-	S is [=parsed as a forgiving selector list=].
+	S is <> [=parsed as a forgiving selector list=].
 	If S is omitted,
 	it defaults to ''*|*''.
 
@@ -2954,6 +2957,9 @@ Child-indexed Pseudo-classes
 		
 	
 
+	Note: We intend to extend '':nth-last-child()'' to accept <>
+	in Level 5.
+
 
 '':first-child'' pseudo-class
 
@@ -4038,6 +4044,8 @@ Changes since the 21 November 2018 Working Draft
 		Defined '':is()'', '':where()'', '':has()'', '':nth-child()'', and '':nth-last-child()''
 			to not be themselves invalidated when containing an invalid selector.
 			(Issue 3264)
+		Limited selectors in '':nth-child()'' and '':nth-last-child()'' to [=compound selectors=] for now.
+			(Issue 3760)
 		Clarified case-sensitive string matching by referencing string identity as defined in [[INFRA]].
 		Clarified that UA-provided placeholder text still triggers '':placeholder-shown''.
 		Rewrote '':focus-visible'' definition for clarity.