Describe the bug

The check whether a type parameter has multiple lower or upper bounds does not work if the type parameter occurs on the right side of a bound. However, X sub Y is the same as Y super X.

To Reproduce

Code:

class C<T1, T2> where {
    T1 sub Int,
    T2 super T1 // there should be an error here
}

Expected behavior

An error should be shown for the second bound of the above example.

Screenshots (optional)

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Additional Context (optional)

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