<p dir="auto"><strong>TypeScript Version:</strong></p>
<p dir="auto">1.7.5 / 1.8.0-beta / nightly (1.9.0-dev.20160217)</p>
<p dir="auto"><strong>Code</strong></p>
<div class="highlight highlight-source-ts notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="// A self-contained demonstration of the problem follows...
"><pre class="notranslate"><span class="pl-c">// A self-contained demonstration of the problem follows...</span></pre></div>
<p dir="auto"><strong>Expected behavior:</strong></p>
<p dir="auto"><strong>Actual behavior:</strong></p>
<p dir="auto">The below code raise an compilation error, which says "Property 'includes' does not exist on type 'string'.", even with the "--target es6" option.</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="&quot;abcde&quot;.includes(&quot;cd&quot;);"><pre class="notranslate"><code class="notranslate">"abcde".includes("cd");
</code></pre></div>
<p dir="auto">It is likely that "contains" function defined in String interface should be replaced with "includes".<br>
<a href="https://github.com/Microsoft/TypeScript/blob/b2a871dcfb89739632fbc0fa5b5abe0177d68b9b/src/lib/es6.d.ts#L380">https://github.com/Microsoft/TypeScript/blob/b2a871dcfb89739632fbc0fa5b5abe0177d68b9b/src/lib/es6.d.ts#L380</a><br>
<a href="https://github.com/Microsoft/TypeScript/blob/965f994acefd238dc0c473e739d7916c47bf41b4/bin/lib.core.es6.d.ts#L1579">https://github.com/Microsoft/TypeScript/blob/965f994acefd238dc0c473e739d7916c47bf41b4/bin/lib.core.es6.d.ts#L1579</a></p>