Function market_diff 

pub fn market_diff(
    before: &MarketContext,
    after: &MarketContext,
) -> Result<MarketDiff, PnlError>

The move from before to after, under the layout guard — with one relaxation. A MarketInputId::Fixing that after holds and before does not is a newly published print, not a move: it is lifted out into MarketDiff::published and the remaining inputs are compared position by position as ever. A print before holds and after does not is refused — a print does not un-publish — and so is every other difference. Markets on different valuation days get no relaxation: their prints are compared like any other input.

Errors

PnlError::LayoutMismatch naming the first position at which the two markets’ lifted inputs differ.