Fix negative values

src/grammar.ne

@@ -50,9 +50,7 @@
 %}
 
 number
-  -> ([0-9]:? "." [0-9]:+) {% d => Number(text(d)) %}
-   | ([1-9] [0-9]:*) {% d => Number(text(d)) %}
-   | "0" {% d => Number(text(d)) %}
+  -> "-":? ([0-9]:? "." [0-9]:+ | [1-9] [0-9]:* | "0") {% d => Number(text(d)) %}
 
 angle -> number ("deg" | "rad") {% text %}
 

src/index.test.js

@@ -26,6 +26,15 @@ it('allows decimal values in transformed values', () => runTest([
   borderBottomLeftRadius: 1.5,
 }));
 
+it('allows negative values in transformed values', () => runTest([
+  ['border-radius', '-1.5'],
+], {
+  borderTopLeftRadius: -1.5,
+  borderTopRightRadius: -1.5,
+  borderBottomRightRadius: -1.5,
+  borderBottomLeftRadius: -1.5,
+}));
+
 it('transforms strings', () => runTest([
   ['color', 'red'],
 ], { color: 'red' }));