<h3 dir="auto">Vue.js version</h3>
<p dir="auto">1.0.27</p>
<h3 dir="auto">Reproduction Link</h3>
<p dir="auto"><a href="https://jsfiddle.net/gckb9mkv/1/" rel="nofollow">https://jsfiddle.net/gckb9mkv/1/</a></p>
<h3 dir="auto">Steps to reproduce</h3>
<p dir="auto">Open the fiddle and check the console output</p>
<h3 dir="auto">What is Expected?</h3>
<p dir="auto">Same code but with 1.0.26 dependencies.<br>
<a href="https://jsfiddle.net/qjvz0p1x/" rel="nofollow">https://jsfiddle.net/qjvz0p1x/</a></p>
<p dir="auto">// p1:Array[2]<br>
// p2:Array[0]<br>
// p3:"toto"</p>
<h3 dir="auto">What is actually happening?</h3>
<p dir="auto">// p1:"a,b"<br>
// p2:true<br>
// p3:"toto"</p>
<h3 dir="auto">Vue.js version</h3>
<p dir="auto">1.0.27</p>
<h3 dir="auto">Description</h3>
<p dir="auto">Parameter data type is illegal to chang</p>
<h3 dir="auto">Reproduction Link</h3>

<p dir="auto"><a href="https://jsfiddle.net/jawc4bpo/" rel="nofollow">jsfiddle</a></p>
<h3 dir="auto">What is Expected?</h3>
<p dir="auto">Here is same <a href="https://jsfiddle.net/gn4aezn2/" rel="nofollow">example</a>  with version 1.0.26 where it works</p>