equality does unit conversions

src/builtin/list.rs

@@ -225,7 +225,10 @@ pub(crate) fn register(f: &mut HashMap<String, Builtin>) {
                 v => vec![v],
             };
             let value = arg!(args, 1, "value");
-            let index = match list.into_iter().position(|v| v == value) {
+            let index = match list
+                .into_iter()
+                .position(|v| v.equals(value.clone()).unwrap())
+            {
                 Some(v) => Number::from(v + 1),
                 None => return Ok(Value::Null),
             };

src/value/mod.rs

@@ -189,6 +189,21 @@ impl Value {
                 Self::Ident(s2, ..) => s1 == s2,
                 _ => false,
             },
+            Self::Dimension(n, unit) => match other {
+                Self::Dimension(n2, unit2) => {
+                    if !unit.comparable(&unit2) {
+                        false
+                    } else if unit == unit2 {
+                        n == n2
+                    } else if unit == Unit::None || unit2 == Unit::None {
+                        false
+                    } else {
+                        n == (n2
+                            * UNIT_CONVERSION_TABLE[&unit.to_string()][&unit2.to_string()].clone())
+                    }
+                }
+                _ => false,
+            },
             s => s == other.eval()?,
         })
     }

tests/list.rs

@@ -293,3 +293,8 @@ test!(
     "a {\n  color: index((width: 10px, height: 20px), (height 20px));\n}\n",
     "a {\n  color: 2;\n}\n"
 );
+test!(
+    index_unit_conversions,
+    "a {\n  color: index(1px 1in 1cm, 96px);\n}\n",
+    "a {\n  color: 2;\n}\n"
+);

tests/number.rs

@@ -86,3 +86,8 @@ test!(
     "a {\n  color: -0.000000000001;\n}\n",
     "a {\n  color: 0;\n}\n"
 );
+test!(
+    equality_unit_conversions,
+    "a {\n  color: 1in == 96px;\n}\n",
+    "a {\n  color: true;\n}\n"
+);