Vito 1c2be05cdc fix: Amendment-gate hybrid (1+r)^n-1 evaluator on fixCleanup3_2_0 ...

Commit 26f82a2a1 swapped `computePaymentFactor` from the cancellation-prone
`power(1+r, n) - 1` to `computePowerMinusOneHybrid`, but did not
amendment-gate the swap. Because the change alters the bit-pattern of
amortization output at near-zero rates, applying it without a gate would
fork consensus on any ledger with a long-running near-zero-rate loan.

Gate the hybrid path on `fixCleanup3_2_0`. When the amendment is not
enabled, `computePaymentFactor` falls back to the original direct
subtraction, preserving pre-fix output bit-exactly. When enabled, the
hybrid path is used and the near-zero-rate regression tests
(`testBugInterestDueDeltaCrash`, `testFullLifecycleVaultPnLNearZeroRate`)
pass.

Threads `Rules const&` from the public lending API down to
`computePaymentFactor`:

- `computePaymentFactor`, `loanPeriodicPayment`,
  `loanPrincipalFromPeriodicPayment` (leaves)
- `computeTheoreticalLoanState`, `computeFullPayment`,
  `computePaymentComponents` (mid-level)
- `computeLoanProperties` (both overloads), `tryOverpayment`,
  `doOverpayment` (top-level)

Public callers (`LoanSet::doApply`, `loanMakePayment`) pass
`view.rules()`. Tests pass `env.current()->rules()`.

2026-04-29 12:17:59 +02:00

..

xrpl

fix: Amendment-gate hybrid (1+r)^n-1 evaluator on fixCleanup3_2_0

2026-04-29 12:17:59 +02:00