repl: make tab completion work on non-objects

lib/repl.js

@@ -523,8 +523,13 @@ REPLServer.prototype.complete = function(line, callback) {
             }
             // works for non-objects
             try {
-              var p = Object.getPrototypeOf(obj);
               var sentinel = 5;
+              var p;
+              if (typeof obj == 'object') {
+                p = Object.getPrototypeOf(obj);
+              } else {
+                p = obj.constructor ? obj.constructor.prototype : null;
+              }
               while (p !== null) {
                 memberGroups.push(Object.getOwnPropertyNames(p));
                 p = Object.getPrototypeOf(p);

test/simple/test-repl-tab-complete.js

@@ -180,3 +180,12 @@ testMe.complete('inner.o', function(error, data) {
   assert.deepEqual(data, doesNotBreak);
 });
 
+putIn.run(['.clear']);
+
+// make sure tab completion works on non-Objects
+putIn.run([
+  'var str = "test";'
+]);
+testMe.complete('str.len', function(error, data) {
+  assert.deepEqual(data, [ [ 'str.length' ], 'str.len' ]);
+});