Avoid throw/catch in Number.== (#1188)

Throwing and catching exceptions is expensive. Testing this on one
user's number-heavy codebase resulted in a 2x speed improvement.

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.32.3
+
+* Optimize `==` for numbers that have different units.
+
 ## 1.32.2
 
 * Print the actual number that was received in unit deprecation warnings for

lib/src/value/number.dart

@@ -620,16 +620,26 @@ class SassNumber extends Value implements ext.SassNumber {
 
   bool operator ==(Object other) {
     if (other is SassNumber) {
-      // Unitless numbers are convertable to unit numbers, but not equal, so we
-      // special-case unitless here.
-      if (hasUnits != other.hasUnits) return false;
+      if (numeratorUnits.length != other.numeratorUnits.length ||
+          denominatorUnits.length != other.denominatorUnits.length) {
+        return false;
+      }
       if (!hasUnits) return fuzzyEquals(value, other.value);
 
-      try {
-        return _coerceUnits(other, fuzzyEquals);
-      } on SassScriptException {
+      if (!listEquals(_canonicalizeUnitList(numeratorUnits),
+              _canonicalizeUnitList(other.numeratorUnits)) ||
+          !listEquals(_canonicalizeUnitList(denominatorUnits),
+              _canonicalizeUnitList(other.denominatorUnits))) {
         return false;
       }
+
+      return fuzzyEquals(
+          value *
+              _canonicalMultiplier(numeratorUnits) /
+              _canonicalMultiplier(denominatorUnits),
+          other.value *
+              _canonicalMultiplier(other.numeratorUnits) /
+              _canonicalMultiplier(other.denominatorUnits));
     } else {
       return false;
     }
@@ -639,6 +649,23 @@ class SassNumber extends Value implements ext.SassNumber {
       _canonicalMultiplier(numeratorUnits) /
       _canonicalMultiplier(denominatorUnits));
 
+  /// Converts a unit list (such as [numeratorUnits]) into an equivalent list in
+  /// a canonical form, to make it easier to check whether two numbers have
+  /// compatible units.
+  List<String> _canonicalizeUnitList(List<String> units) {
+    if (units.isEmpty) return units;
+    if (units.length == 1) {
+      var type = _typesByUnit[units.first];
+      return type == null ? units : [_unitsByType[type].first];
+    }
+
+    return units.map((unit) {
+      var type = _typesByUnit[unit];
+      return type == null ? unit : _unitsByType[type].first;
+    }).toList()
+      ..sort();
+  }
+
   /// Returns a multiplier that encapsulates unit equivalence in [units].
   ///
   /// That is, if `X units1 == Y units2`, `X * _canonicalMultiplier(units1) == Y

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.32.2
+version: 1.32.3
 description: A Sass implementation in Dart.
 author: Sass Team
 homepage: https://github.com/sass/dart-sass