title: With eslint-plugin-flowtype, how to check if a type exist
body: <p>I enabled <code>eslint-plugin-flowtype</code> with Flow on a React project. It's work well but not perfect. I have for example the error <code>Missing return type annotation. (flowtype/require-return-type)</code> that raised for missing returned type. But I have no error when I write an unknown type. For example, writing <code>{dispatch: TotoType}</code> doesn't raise any error (<code>TotoType</code> is not declared).</p>
  <h3>To be more clear:</h3>
  <p>My issue is that if I write a type that does not exist (I mean <code>nomber</code> instead <code>number</code>), Flowtype eslint plugin does not return any errors. The error should be triggered whenever I use it but it is not the case :(. If I use Flow CLI on my file, I got the error like <code>unknown Type</code>. I want to have the FlowType ESlint plugin lints the same errors.</p>
  <p>I'm using <a href="https://github.com/lowik/eslint-config-evenium" rel="nofollow noreferrer">eslint-config-evenium</a> configuration file that provide those rules:</p>
  <pre><code>{
      ...
      &quot;rules&quot;: {
  
          &quot;flowtype/boolean-style&quot;: [
              2,
              &quot;boolean&quot;
          ],
          &quot;flowtype/define-flow-type&quot;: 1,
          &quot;flowtype/delimiter-dangle&quot;: [
              2,
              &quot;never&quot;
          ],
          &quot;flowtype/generic-spacing&quot;: [
              2,
              &quot;never&quot;
          ],
          &quot;flowtype/no-primitive-constructor-types&quot;: 2,
          &quot;flowtype/no-weak-types&quot;: 0,
          &quot;flowtype/object-type-delimiter&quot;: [
              2,
              &quot;comma&quot;
          ],
          &quot;flowtype/require-parameter-type&quot;: 2,
          &quot;flowtype/require-return-type&quot;: [
              2,
              &quot;always&quot;,
              {
                  &quot;annotateUndefined&quot;: &quot;never&quot;,
                  &quot;excludeArrowFunctions&quot;: true  
              }
          ],
          &quot;flowtype/require-valid-file-annotation&quot;: 2,
          &quot;flowtype/semi&quot;: [
              2,
              &quot;always&quot;
          ],
          &quot;flowtype/space-after-type-colon&quot;: [
              2,
              &quot;always&quot;
          ],
          &quot;flowtype/space-before-generic-bracket&quot;: [
              2,
              &quot;never&quot;
          ],
          &quot;flowtype/space-before-type-colon&quot;: [
              2,
              &quot;never&quot;
          ],
          &quot;flowtype/type-id-match&quot;: [
              2,
              &quot;^([A-Z][a-z0-9]+)+Type$&quot;
          ],
          &quot;flowtype/union-intersection-spacing&quot;: [
              2,
              &quot;always&quot;
          ],
          &quot;flowtype/use-flow-type&quot;: 1,
          &quot;flowtype/valid-syntax&quot;: 1
      },
      &quot;settings&quot;: {
          &quot;flowtype&quot;: {
              &quot;onlyFilesWithFlowAnnotation&quot;: true
          }
      }
  }
  </code></pre>
  <p>How to have ESlint generating an error for unauthorized type?
  And if possible, I'll appreciate to be able to add unexisting Type to the list a authorized type.</p>
  <p>Anyone know how to do that or if it is even possible?</p>