This is something that came up multiple times. I think type information is especially valuable in combination with other IDE features (code completion).

My idea was to do type checking in a separate tool (e.g. built on top of Buildifier) and let the interpreter ignore the types. So it could be completely optional. The type system could be gradual, like in Typescript.

I don't know when/if it will happen (I'm no longer working at Google, so it's harder to make large contributions like this).