Simplify negate value (#5389)

* simplify `negateValue`

Co-authored-by: Brad Cornes <bradlc41@gmail.com>

* ensure we have the exact same behaviour

* Simplify/loosen regex to be more future-proof

Co-authored-by: Brad Cornes <bradlc41@gmail.com>
Co-authored-by: Adam Wathan <adam.wathan@gmail.com>

src/util/negateValue.js

@@ -1,9 +1,14 @@
-import reduceCalc from 'reduce-css-calc'
-
 export default function (value) {
-  try {
-    return reduceCalc(`calc(${value} * -1)`)
-  } catch (e) {
-    return value
+  value = `${value}`
+
+  // Flip sign of numbers
+  if (/^[+-]?(\d+|\d*\.\d+)(e[+-]?\d+)?(%|\w+)?$/.test(value)) {
+    return value.replace(/^[+-]?/, (sign) => (sign === '-' ? '' : '-'))
   }
+
+  if (value.includes('var(') || value.includes('calc(')) {
+    return `calc(${value} * -1)`
+  }
+
+  return value
 }