[Bug]: typespec-python - discriminated polymorphic types as op parameters generated incorrectly

[johanste]

Describe the bug

We type base[] as list[base] in method parameters. That does not compute with polymorphic types.

Reproduction

@service()
namespace PolymorphicVariance;

@discriminator("kind")
model Pet {
  kind: string;
}

model Cat extends Pet {
  kind: "cat"
}

model Dog extends Pet {
  kind: "dog"
}

op cuddle(ingredients: Pet[]): void;

repro.py

cuddle([Dog(), Cat()])

$> pyright repro.py

Checklist

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• The provided reproduction is a minimal reproducible example of the bug.

[johanste]

And to clarify, the parameter type needs to be a covariant ordered collection type (e.g. Iterable or - in theory - Sequence - but Sequence would impose to constraints on the input that we actually don't need) rather than an invariant type because an invariant type means that list can only contain the very specific type in the list.