From 4d54c5d3513521e7446fd833a95c8d8d40593c97 Mon Sep 17 00:00:00 2001
From: Natalie Weizenbaum <nex342@gmail.com>
Date: Tue, 18 Oct 2016 16:48:42 -0700
Subject: [PATCH] Fix units for coercing number operations.

---
 lib/src/value/number.dart | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/lib/src/value/number.dart b/lib/src/value/number.dart
index b805df30..e7b6c49f 100644
--- a/lib/src/value/number.dart
+++ b/lib/src/value/number.dart
@@ -418,24 +418,24 @@ class SassNumber extends Value {
     throw new SassScriptException('Undefined operation "$this <= $other".');
   }
 
-  Value modulo(Value other) {
+  SassNumber modulo(Value other) {
     if (other is SassNumber) {
-      return new SassNumber(_coerceUnits(other, (num1, num2) => num1 % num2));
+      return _coerceNumber(other, (num1, num2) => num1 % num2);
     }
     throw new SassScriptException('Undefined operation "$this % $other".');
   }
 
-  Value plus(Value other) {
+  SassNumber plus(Value other) {
     if (other is SassNumber) {
-      return new SassNumber(_coerceUnits(other, (num1, num2) => num1 + num2));
+      return _coerceNumber(other, (num1, num2) => num1 + num2);
     }
     if (other is! SassColor) return super.plus(other);
     throw new SassScriptException('Undefined operation "$this + $other".');
   }
 
-  Value minus(Value other) {
+  SassNumber minus(Value other) {
     if (other is SassNumber) {
-      return new SassNumber(_coerceUnits(other, (num1, num2) => num1 - num2));
+      return _coerceNumber(other, (num1, num2) => num1 - num2);
     }
     if (other is! SassColor) return super.minus(other);
     throw new SassScriptException('Undefined operation "$this - $other".');
@@ -476,6 +476,20 @@ class SassNumber extends Value {
 
   Value unaryMinus() => new SassNumber(-value);
 
+  /// Converts [other]'s value to be compatible with this number's, calls
+  /// [operation] with the resulting numbers, and wraps the result in a
+  /// [SassNumber].
+  ///
+  /// Throws a [SassScriptException] if the two numbers' units are incompatible.
+  SassNumber _coerceNumber(
+      SassNumber other, num operation(num num1, num num2)) {
+    var result = _coerceUnits(other, operation);
+    return new SassNumber.withUnits(result,
+        numeratorUnits: hasUnits ? this.numeratorUnits : other.numeratorUnits,
+        denominatorUnits:
+            hasUnits ? this.denominatorUnits : other.denominatorUnits);
+  }
+
   /// Converts [other]'s value to be compatible with this number's, and calls
   /// [operation] with the resulting numbers.
   ///