title: Assessing a Function's Argument Types From Tuple
body: <p>I am trying to use tuple type as function argument's type.</p>
  <pre class="lang-js prettyprint-override"><code>type T_a = (a1: string, a2: number) =&gt; boolean
  const a: T_a = (a1, a2) =&gt; a1.length &gt;= a2
  
  type T_b_arguments = [number, string]
  type T_b = (...T_b_arguments) =&gt; boolean
  const b: T_b = (b1, b2) =&gt; b1 &lt; b2.length
  
  // Example:
  b(1, 'mystring) // true
  </code></pre>
  <p><a href="https://www.typescriptlang.org/play?ssl=6&amp;ssc=42&amp;pln=1&amp;pc=1#code/C4TwDgpgBAKg%20gQygXigCgQRgFxQM7ABOAlgHYDmANFAgEy6kCuAtgEYSECUKAfFKwHsBAGwgJSAKADGA0gRq54SVBkzU63ZHywA6URWAALKD1R0JE0JFhxWiQuRYRSwPCigBtJmw7UCJCgBdS3BoeFZ3NB1o8PtHZmdXTT5BETFJGTlgfkVbSNY1flpk-kwoAB4ivWdyIyA" rel="nofollow noreferrer">Typescript playground</a></p>
  <p>How can I do this?</p>