path: Do not coerce paths to strings on Windows

Fix #4795

lib/path.js

@@ -448,7 +448,9 @@ exports.existsSync = util.deprecate(function(path) {
 
 if (isWindows) {
   exports._makeLong = function(path) {
-    path = '' + path;
+    if (typeof path !== 'string')
+      return path;
+
     if (!path) {
       return '';
     }

test/simple/test-path-makelong.js

@@ -19,11 +19,11 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-if (process.platform === 'win32') {
 var assert = require('assert');
 var path = require('path');
 var common = require('../common');
 
+if (process.platform === 'win32') {
   var file = path.join(common.fixturesDir, 'a.js');
   var resolvedFile = path.resolve(file);
 
@@ -36,3 +36,9 @@ if (process.platform === 'win32') {
   assert.equal('\\\\.\\pipe\\somepipe',
                path._makeLong('\\\\.\\pipe\\somepipe'));
 }
+
+assert.equal(path._makeLong(null), null);
+assert.equal(path._makeLong(100), 100);
+assert.equal(path._makeLong(path), path);
+assert.equal(path._makeLong(false), false);
+assert.equal(path._makeLong(true), true);