Fix index on mixed units error. Fixes #1228

Author: lukeapage

lib/less/tree/rule.js

@@ -21,9 +21,16 @@ tree.Rule.prototype = {
     toCSS: function (env) {
         if (this.variable) { return "" }
         else {
-            return this.name + (env.compress ? ':' : ': ') +
+            try {
+                return this.name + (env.compress ? ':' : ': ') +
                    this.value.toCSS(env) +
                    this.important + (this.inline ? "" : ";");
+            }
+            catch(e) {
+                e.index = this.index;
+                e.filename = this.currentFileInfo.filename;
+                throw e;
+            }
         }
     },
     eval: function (env) {

test/less/errors/divide-mixed-units.txt

@@ -1,2 +1,4 @@
-SyntaxError: Multiple units in dimension. Correct the units or use the unit function. Bad unit: px/em in {path}divide-mixed-units.less on line null, column 0:
-1   error: (1px / 3em);
+SyntaxError: Multiple units in dimension. Correct the units or use the unit function. Bad unit: px/em in {path}divide-mixed-units.less on line 2, column 3:
+1 .a {
+2   error: (1px / 3em);
+3 }

test/less/errors/multiply-mixed-units.less

@@ -1,3 +1,7 @@
+/* Test */
+#blah {
+  // blah
+}
 .a {
   error: (1px * 1em);
 }

test/less/errors/multiply-mixed-units.txt

@@ -1,2 +1,4 @@
-SyntaxError: Multiple units in dimension. Correct the units or use the unit function. Bad unit: em*px in {path}multiply-mixed-units.less on line null, column 0:
-1   error: (1px * 1em);
+SyntaxError: Multiple units in dimension. Correct the units or use the unit function. Bad unit: em*px in {path}multiply-mixed-units.less on line 6, column 3:
+5 .a {
+6   error: (1px * 1em);
+7 }