Function risky_on_view 

fn risky_on_view<R: Scalar>(
    flows: &[(NaiveDate, R)],
    face_at: impl Fn(NaiveDate) -> f64,
    maturity: NaiveDate,
    view: &PricingView<'_, R>,
    product: &'static str,
) -> Result<R, PricingError>

The survival-weighted value of flows with the view’s credit, refusing a view without a market recovery — a hand-built view lacking one is a missing input, not a zero-recovery price.