Go-to-type definition does not work on aliases to tuple types

```ts
export type SpanMapping = [
  virtualStart: number,
  virtualLength: number,
  originalStart: number,
  originalLength: number,
  kind: SpanMapKind,
  features?: SpanMapFeature,
];
export let mapping: SpanMapping;
mapping/**/;
```

If you request *go to type definition* at `/**/`, you will get no result.

The same is not true if `SpanMapping` is aliased to an anonymous object type.