title: Inadvertent use of = instead of ==
body: <p>It seems that </p>
  
  <pre><code>if (x=y) { .... }
  </code></pre>
  
  <p>instead of</p>
  
  <pre><code>if (x==y) { ... } 
  </code></pre>
  
  <p>is a root of many evils.</p>
  
  <p>Why don't <em>all</em> compilers <em>mark it as error</em> instead of a configurable warning?</p>
  
  <p>I'm interested in finding out cases where the construct <code>if (x=y)</code> is useful.</p>