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      <base href="https://bugs.webkit.org/" />
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - DFG Validation fails when performing a concatenation with only a single entry"
   href="https://bugs.webkit.org/show_bug.cgi?id=158699">158699</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>DFG Validation fails when performing a concatenation with only a single entry
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>WebKit
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>WebKit Nightly Build
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Unspecified
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Unspecified
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Keywords</th>
          <td>NeedsRadar
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>Normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P2
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>JavaScriptCore
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>webkit-unassigned&#64;lists.webkit.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>oliver&#64;apple.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>fpizlo&#64;apple.com, sbarati&#64;apple.com
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Fairly simple failure:

function f() {
    for (;;)`${1}`
}
f();

The issue is that we appear to be issuing a str_concat with a single child, which the DFG thinks is invalid. The obvious solutions are to either:
* don't emit str_concat from a single child template literal
* Have the DFG acknowledge this can happen

I think the former is the better option.</pre>
        </div>
      </p>
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