title: Can I force Typescript to allow dot notation
body: <p>I want to be able to suppress the compile time error that I get from Typescript where I use dot notation to access a property that the compiler doesn't know about. Access with bracket notation works, but dot notation gives a compile error.</p>
  
  <p>My specific case is that I have added a custom matcher (call it 'toLookLike') to Jasmine using Angular. I can use it with brackets notation:</p>
  
  <pre><code>expect(something)['toLookLike'](otherthing);
  </code></pre>
  
  <p>but using dot notation would be much more readable</p>
  
  <pre><code>expect(something).toLookLike(otherthing);
  </code></pre>
  
  <p>But the matcher is added at runtime and the compiler doesn't know about it, so I get a compile error if I use the dot notation.</p>
  
  <p><strong>Is there a way to tell Typescript that dot notation is OK in this case?</strong> I'd be happy with doing it once, or on every line where the method is used. I do not of course have the ability to add toLookLike to the definition of the jasmine Matcher object.</p>
  
  <p>I'm very familiar with the issues around allowing general dot notation for undefined properties, and in this specific case I'm prepared to take the risk. I don't need an explanation of why dot notation is prohibited in the general case. I've also read and understood <a href="https://stackoverflow.com/questions/30089879/typescript-and-dot-notation-access-to-objects">this question</a>.</p>