color addition is undefined

src/value/ops.rs

@@ -4,7 +4,7 @@ use crate::common::QuoteKind;
 use crate::error::SassResult;
 use crate::units::Unit;
 use crate::value::Value;
-// Undefined operation "red + white".
+
 impl Add for Value {
     type Output = SassResult<Self>;
 
@@ -30,16 +30,17 @@ impl Add for Value {
                     };
                     Value::Ident(format!("{}{}{}", num, unit, s), quotes)
                 }
+                Self::Null => Value::Ident(format!("{}{}", num, unit), QuoteKind::None),
                 _ => todo!(),
             },
             // Self::List(..) => todo!(),
-            Self::Color(c) => match other {
+            Self::Color(c) => match dbg!(&other) {
                 Self::Ident(s, QuoteKind::Double) | Self::Ident(s, QuoteKind::Single) => {
                     Value::Ident(format!("{}{}", c, s), QuoteKind::Double)
                 }
+                Self::Ident(s, QuoteKind::None) => Value::Ident(format!("{}{}", c, s), QuoteKind::None),
                 Self::Null => Value::Ident(c.to_string(), QuoteKind::None),
-                Self::Color(..) => todo!("figure out if it's possible to add colors"),
+                _ => return Err(format!("Undefined operation \"{} + {}\".", c, other).into()),
-                _ => Value::Ident(format!("{}{}", c, other), QuoteKind::None),
             },
             // Self::BinaryOp(..) => todo!(),
             // Self::Paren(..) => todo!(),

tests/values.rs

@@ -321,3 +321,19 @@ test!(
 );
 test!(positive_float_leading_zero, "a {\n  color: 0.1;\n}\n");
 test!(negative_float_leading_zero, "a {\n  color: -0.1;\n}\n");
+test!(
+    unitless_plus_null,
+    "a {\n  color: 1 + null;\n}\n",
+    "a {\n  color: 1;\n}\n"
+);
+// blocked on proper parsing of binary ops
+// test!(
+//     unitless_plus_null_plus_unitless,
+//     "a {\n  color: 1 + null + 1;\n}\n",
+//     "a {\n  color: 11;\n}\n"
+// );
+test!(
+    unit_plus_null,
+    "a {\n  color: 1px + null;\n}\n",
+    "a {\n  color: 1px;\n}\n"
+);