handle percent op none

src/unit/mod.rs

@@ -114,10 +114,13 @@ pub(crate) enum UnitKind {
 
 impl Unit {
     pub fn comparable(&self, other: &Unit) -> bool {
+        if other == &Unit::None {
+            return true;
+        }
         match self.kind() {
             UnitKind::FontRelative | UnitKind::ViewportRelative | UnitKind::Other => self == other,
             UnitKind::None => true,
-            u => other.kind() == u || other.kind() == UnitKind::None,
+            u => other.kind() == u,
         }
     }
 

tests/units.rs

@@ -64,6 +64,11 @@ test!(
     "a {\n  color: 10 - 10px;\n}\n",
     "a {\n  color: 0px;\n}\n"
 );
+test!(
+    percent_plus_none,
+    "a {\n  color: 10% + 10;\n}\n",
+    "a {\n  color: 20%;\n}\n"
+);
 
 macro_rules! test_unit_addition {
     ($u1:ident, $u2:ident, $out:literal) => {