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PSA: you can typically declare different types of string so that your type system objects to mixing data of different types even though deep down we know they're both strings.

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If you mean type aliases, that's a good idea within a single codebase, but the distinction between different types of strings doesn't survive serialization so it wouldn't have prevented this error. What they need is a way to signal errors out-of-band, like Result<T> or exceptions.

In python, aliases are separate from typing.NewType, but you're right: it's only enforced within a codebase and then only if the dev cares to run the typechecker.

So yeah, I guess it either needs to happen at runtime, or we just do signaling and user data on separate file descriptors.

This is presuming that the type system is nomitive rather than structural and there is not serialisation/deserialisation or type refinement occurring. A structural difference is much more preferable.

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