[tayo42]

In some cases don't you need to actually execute the code to know what the type actually is. How does the type checker know then?

[maleldil]

It doesn't. There are cases where the type-checker can't know the type (e.g. json.load has to return Any), but there are tools in the language to reduce how much that happens. If you commit to a fully strictly-typed codebase, it doesn't happen often.

[sevensor]

You can actually annotate the return type of json.load better than that:

    JSON = float | bool | int | str | None | list[“JSON”] | dict[str, “JSON”]