Arbitrary (non-falsey) values returned from functions are cast as Anonymous nodes

test/css/functions.css

@@ -38,7 +38,7 @@
   saturate-filter: saturate(5%);
   contrast-white: #000000;
   contrast-black: #ffffff;
-  contrast-red: #000000;
+  contrast-red: #ffffff;
   contrast-green: #000000;
   contrast-blue: #ffffff;
   contrast-yellow: #000000;
@@ -49,11 +49,11 @@
   contrast-light-thresh: #111111;
   contrast-dark-thresh: #eeeeee;
   contrast-high-thresh: #eeeeee;
-  contrast-low-thresh: #eeeeee;
+  contrast-low-thresh: #111111;
   contrast-light-thresh-per: #111111;
   contrast-dark-thresh-per: #eeeeee;
   contrast-high-thresh-per: #eeeeee;
-  contrast-low-thresh-per: #eeeeee;
+  contrast-low-thresh-per: #111111;
   replace: "Hello, World!";
   replace-captured: "This is a new string.";
   replace-with-flags: "2 + 2 = 4";

test/css/plugin.css

@@ -50,4 +50,7 @@
   val1: foo;
   val2: foo;
 }
+.test-simple {
+  value: 3.141592653589793;
+}
 @arbitrary value after ();

test/less/plugin.less

@@ -91,6 +91,10 @@
   test-collapse();
   val2: foo;
 }
+.test-simple {
+  @plugin "./plugin/plugin-simple";
+  value: pi();
+}
 
 test-atrule("@charset"; '"utf-8"');
 test-atrule("@arbitrary"; "value after ()");

test/less/plugin/plugin-simple.js

@@ -0,0 +1,3 @@
+functions.add('pi', function() {
+    return Math.PI;
+});