TypeError when optional params omitted from array

[bakerkretzmar]

Given this route:

const routes = {
    'posts.comments.show': {
        uri: 'posts/{post}/comments/{comment?}',
        methods: ['GET', 'HEAD'],
        parameters: ['post', 'comment'],
    },
};

Which generates these types:

interface RouteList {
    'posts.comments.show': [
        { name: 'post'; required: true },
        { name: 'comment'; required: false },
    ];
}

These valid route() calls, which should not cause any type errors, do:

route('posts.comments.show', [2]);
route('posts.comments.show', ['foo']);
route('posts.comments.show', [{ id: 2 }]);

The issue is that our type for an array of parameters doesn't specify any of them as optional (except additional unknown params after the ones we're expecting), so e.g. passing an array with less than 2 items will error if the route has 2 parameters, even if some of them are optional.

After #697 I'm hoping this will be possible to fix.