title: C# 7 Out variable and pattern variable declarations are not allowed within a query clause
body: <p>Why out variables are not allowed in query clause?</p>
  
  <p>If I use out variables here it fails:</p>
  
  <pre><code>string json = "{'PayDays':['2017-07-07','2017-07-21','2017-08-04','2017-08-18']}";
  var pd = JsonConvert.DeserializeObject&lt;Accounting&gt;(json);
  
  var rm = from item in pd.PayDays
       where (DateTime.TryParse(item, out DateTime dateresult)) ?
      dateresult.Subtract(DateTime.Now).Days &gt;= 0 ? true : false : false      
      select item;
  rm.Dump();
  </code></pre>
  
  <p>But old way works:</p>
  
  <pre><code>DateTime result;
  var rm = from item in pd.PayDays
           where DateTime.TryParse(item, out result) ? (result.Subtract(DateTime.Now).Days &gt;= 0 ? true : false) : false
           select item;
  rm.Dump();
  </code></pre>