no-unused-prop-types is unable to parse type aliases

no-unused-prop-types v.7.4.0 throws when trying to parse this code

type SomeProps = {};
type DefaultProps = SomeProps;
type Props = DefaultProps & {};
export class TestComponent extends React.Component<Props, void> {}

TypeError: Cannot read property 'length' of undefined
    at iterateProperties (eslint-plugin-react/lib/rules/no-unused-prop-types.js:336:21)
    at declarePropTypesForObjectTypeAnnotation (eslint-plugin-react/lib/rules/no-unused-prop-types.js:725:7)
    at propTypes.types.some.annotation (eslint-plugin-react/lib/rules/no-unused-prop-types.js:767:16)

[k15a]

Yes, this is valid Syntax. You can read more about them here: https://flow.org/en/docs/types/typeof/

[jseminck]

Thanks for the report.

I did some quick digging and reproduced the issue. Additionally I found that the following code did parse correctly, but did not detect unused prop-types:

        type SomeProps = {
          firstname: string
        }
        type Props = SomeProps;
        export class TestComponent extends React.Component<Props, void> {
          render() {
            return <div>{this.props.foo}</div>
          }
        }

I have managed to get both cases working (your example + the above). I’ll try to get a PR in within the next few days (as I’m currently travelling a bit).