move logic for checking if array can be treated as #and to utils

lib/dialects/abstract/query-generator.js

@@ -1175,15 +1175,7 @@ module.exports = (function() {
       } else if (Buffer.isBuffer(smth)) {
         result = this.escape(smth);
       } else if (Array.isArray(smth)) {
-        var treatAsAnd = smth.reduce(function(treatAsAnd, arg) {
-          if (treatAsAnd) {
-            return treatAsAnd;
-          } else {
-            return !(arg instanceof Date) && ((arg instanceof Utils.and) || (arg instanceof Utils.or) || Utils._.isPlainObject(arg));
-          }
-        }, false);
-
-        if (treatAsAnd) {
+        if (Utils.canTreatArrayAsAnd(smth)) {
           var _smth = self.sequelize.and.apply(null, smth);
           result = self.getWhereConditions(_smth, tableName, factory, options, prepend);
         } else {

lib/utils.js

@@ -354,6 +354,16 @@ var Utils = module.exports = {
     }
     return result;
   },
+  canTreatArrayAsAnd: function(arr) {
+    return arr.reduce(function(treatAsAnd, arg) {
+      if (treatAsAnd) {
+        return treatAsAnd;
+      } else {
+        return !(arg instanceof Date) && ((arg instanceof Utils.and) || (arg instanceof Utils.or) || Utils._.isPlainObject(arg));
+      }
+    }, false);
+  },
+
   combineTableNames: function(tableName1, tableName2) {
     return (tableName1.toLowerCase() < tableName2.toLowerCase()) ? (tableName1 + tableName2) : (tableName2 + tableName1);
   },