Retain comments before AST_Constants during mangle.

test/mocha/comment_before_constant.js

@@ -0,0 +1,27 @@
+var Uglify = require('../../');
+var assert = require("assert");
+
+describe("comment before constant", function() {
+    var js = 'function f() { /*c1*/ var /*c2*/ foo = /*c3*/ false; return foo; }';
+
+    it("Should test comment before constant is retained and output after mangle.", function() {
+        var result = Uglify.minify(js, {
+            fromString: true,
+            compress: { collapse_vars: false },
+            mangle: {},
+            output: { comments: true },
+        });
+        assert.strictEqual(result.code, 'function f(){/*c1*/var/*c2*/n=/*c3*/!1;return n}');
+    });
+
+    it("Should test code works when comments disabled.", function() {
+        var result = Uglify.minify(js, {
+            fromString: true,
+            compress: { collapse_vars: false },
+            mangle: {},
+            output: {},
+        });
+        assert.strictEqual(result.code, 'function f(){var n=!1;return n}');
+    });
+});
+