title: Do import statements in Swift have an associated cost?
body: <p>Reading the String Manifesto, I saw <a href="https://github.com/apple/swift/blob/master/docs/StringManifesto.md#batteries-included" rel="noreferrer">a paragraph</a> about avoiding the <code>Foundation</code> import when not necessary.</p>
  
  <p>Why is this a concern to the Swift team? Apart from aesthetics and code tidiness, do imports come with a cost? </p>
  
  <p>Could importing unnecessary frameworks impact performance, memory usage, packaged app size or build time?</p>