Format declarations for atrules

lib/formatAtRules.js

@@ -24,6 +24,7 @@ function formatAtRules (root) {
         } else {
           atruleBefore = '\n\n' + getIndent(atrule)
         }
+        formatDecls(atrule)
       }
       if (parentType === 'rule') {
         if (atrule.parent.first === atrule) {

test/fixtures/nested-mixin.css

@@ -0,0 +1,12 @@
+@mixin test() {
+  $values: blue red;
+  @each $val in $values {
+    color: $val;
+    @for $i from 2 through 10 {
+     background: $i;
+    }
+  }
+  @for $i from 2 through 10 {
+    color: $i;
+  }
+}

test/fixtures/nested-mixin.out.css

@@ -0,0 +1,15 @@
+@mixin test() {
+  $values: blue red;
+
+  @each $val in $values {
+    color: $val;
+
+    @for $i from 2 through 10 {
+      background: $i;
+    }
+  }
+
+  @for $i from 2 through 10 {
+    color: $i;
+  }
+}

test/index.js

@@ -28,6 +28,7 @@ test('comment')
 test('comment-in-rules')
 test('vendor-prefix')
 test('nested-atrule')
+test('nested-mixin')
 test('font-face')
 test('import')
 test('pseudo-element')