DataSource Autocompletion support

I want DataSource support in the intellisense recommendations.

I'm using DataSource class everywhere to make resolvers as thin as possible and use its caching abilities.
However, I had to write almost all of my code related with database and REST APIs in classes extending DataSource, and the intellisense does not recognize functions in other DataSource classes I'm referencing through the context.

So I have to lookup the files all the time which is very uncomfortable. It even makes me want to stop using DataSource at all. Coding takes about 1.5 times longer than not using DataSource mostly due to this.

Would it be possible to make intellisense work between different datasource files? That would be so terrific.

No file, test, or entry point is named. Start by locating the TypeScript intellisense implementation and tracing how DataSource references are resolved across files; done means recommendations expose functions from referenced DataSource classes.

Written by the indexing model from the issue text.