Error early if callback argument to .query is not a function

closes mysqljs#1060

Author: dougwilson

Changes.md

@@ -7,6 +7,7 @@ you spot any mistakes.
 ## HEAD
 
 * Delay implied connect until after `.query` argument validation
+* Error early if `callback` argument to `.query` is not a function #1060
 * Lazy-load modules from many entry point; reduced memory use
 
 ## v2.6.2 (2015-04-14)

lib/Connection.js

@@ -67,6 +67,10 @@ Connection.createQuery = function createQuery(sql, values, callback) {
     options.values = undefined;
   }
 
+  if (cb === undefined && callback !== undefined) {
+    throw new TypeError('argument callback must be a function when provided');
+  }
+
   return new Query(options, cb);
 };