Comment by debugnik
2 days ago
It just isn't good enough. Anytime Pyright gives up in type checking, which is often, it simply decays the type into one involving Any/"Unknown":
Without strict settings, it will let you pass this value as of any other type and introduce a bug.
But with strict settings, it will prevent you from recovering the actual type dynamically with type guards, because it flags the existence of the untyped expression itself, even if used in a sound way, which defeats the point of using a gradual checker.
Gradual type systems can and should keep the typed fragment sound, not just give up or (figuratively) panic.
Personally I’ve handled this by just ignoring the gradual part and keeping everything strictly typed. This sometimes requires some awkwardness, such as declaring a variable for an expression I would otherwise just write inline as part of another expression, because Pyright couldn’t infer the type and you need to declare a variable in order to explicitly specify a type. Still, I’ve been quite satisfied with the results. However, this is mostly in the context of new, small, mostly single-author Python codebases; I imagine it would be more annoying in other contexts.