“Use Legacy Swift Language Version” (SWIFT_VERSION) is required to be configured correctly for targets which use Swift."
<p>Ever since I've updated to Xcode 8.2 (GM seed, from the App Store), I have been stuck at the following error:</p>

<blockquote>
  <p>Use Legacy Swift Language Version” (SWIFT_VERSION) is required to be
  configured correctly for targets which use Swift. Use the [Edit >
  Convert > To Current Swift Syntax…] menu to choose a Swift version or
  use the Build Settings editor to configure the build setting directly.</p>
</blockquote>

<p>So I went to my target's <strong>Build Settings</strong>, and searched for <strong><code>SWIFT_VERSION</code></strong> to see where I was erring. However, I was surprised to find that it  was already set to <strong><code>No</code></strong>!</p>

<p>How do I fix this?</p>