From a833e105b78ac3949dedefa910753dfeddd0fca5 Mon Sep 17 00:00:00 2001
From: Adrian Cochrane <adrian@openwork.nz>
Date: Tue, 21 Apr 2020 19:16:37 +1200
Subject: [PATCH] Support lowering single-arg psuedoclasses.

---
 src/Data/CSS/Preprocessor/PsuedoClasses.hs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/Data/CSS/Preprocessor/PsuedoClasses.hs b/src/Data/CSS/Preprocessor/PsuedoClasses.hs
index 13e0d9c..d6c99c4 100644
--- a/src/Data/CSS/Preprocessor/PsuedoClasses.hs
+++ b/src/Data/CSS/Preprocessor/PsuedoClasses.hs
@@ -34,5 +34,8 @@ lowerSelector rewrites (Sibling sib sel') = Sibling sib $ lowerSelector' rewrite
 lowerSelector' :: HashMap Text [Token] -> [SimpleSelector] -> [SimpleSelector]
 lowerSelector' rewrites (Psuedoclass name []:sels)
     | Just value <- name `HM.lookup` rewrites = Psuedoclass "where" value : lowerSelector' rewrites sels
+lowerSelector' rewrites (Psuedoclass name [arg]:sels)
+    | Just value <- name `HM.lookup` rewrites =
+        Psuedoclass "where" [if a == Ident "_" then arg else a | a <- value] : lowerSelector' rewrites sels
 lowerSelector' rewrites (sel:sels) = sel : lowerSelector' rewrites sels
 lowerSelector' _ [] = []
-- 
2.30.2