Function degenerate_dot_kind 

pub fn degenerate_dot_kind<T>(
    config: &DotGeneralConfig,
    lhs_shape: &[T],
    rhs_shape: &[T],
) -> Option<DegenerateDotKind>
where
    T: PartialEq,

Classify a DotGeneral whose algebra is not a contraction.

Returns None when the form is a real contraction (or a shape this rule does not model), so callers fall through to their general path.