fix(token-analyzer): avoid underflow in transfer fee calculation#1066
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mev15 wants to merge 1 commit into
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fix(token-analyzer): avoid underflow in transfer fee calculation#1066mev15 wants to merge 1 commit into
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calculate_fee evaluated the inbound fee as `balance_before_in + (amount - balance_after_in)`. The inner subtraction underflows when the settlement already holds more of a fee-on-transfer token than the per-transfer fee, so it returned Err and the token was misclassified as Bad. Evaluate `(balance_before_in + amount) - balance_after_in` instead, restoring the original left-associative order. Apply the same fix to the recipient leg and add unit tests for the prior-balance and zero-balance cases. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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calculate_feecomputed the inbound fee asbalance_before_in + (amount - balance_after_in). The inneramount - balance_after_inunderflows when the settlement contract already holds more of a fee-on-transfer token than the per-transfer fee, so the function returnedErrand the token was misclassified as Bad — the source of the frequent "Failed to calculate transfer fee: overflow" logs. Tokens the settlement holds none of (e.g. sDAI) were unaffected.Computing
(balance_before_in + amount) - balance_after_inrestores the original left-associative order from before the checked-arithmetic rewrite. The recipient leg gets the same change.Adds two unit tests in common.rs: one reproduces the underflow (settlement holds a prior balance above the fee), one covers the zero-prior-balance case.