Is your feature request related to a problem?

Since we don't allow multiple inheritance or the use of union types in any out-position, we should likewise only allow one upper and one lower bound for type parameters.

Desired solution

Add a check on any subsequent type parameter bounds after the first. Having one upper and one lower bound is OK.

For any computation involving type parameter bounds, only consider the first upper/lower bound.

Possible alternatives (optional)

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