fix: agree rejects nonsense tolerances itself - #281
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`agree` accepted a negative tolerance and accepted a pair with no positive tolerance, leaving both to callers. That was wrong, and the natspec claiming tolerance validity is the caller's business was wrong with it. A negative tolerance cannot mean anything. The spread is a distance, so it is non-negative: `spread <= negative` is unsatisfiable on its own, and under the `max` the negative term is inert — it cannot cancel the other term, only fail to be it. It is representable solely because floats are signed. Accepting it meant a closeness check built on a malformed tolerance silently passed on the other term. Neither tolerance positive is a tolerance of nothing: the limit is zero and `agree` degenerates into exact equality, which `eq` answers directly and more cheaply. A caller that meant to set a tolerance and set none was being misunderstood rather than served. Both are now rejected in `agree`, with `AgreeToleranceNegative` and `AgreeNoPositiveTolerance` carrying the offending tolerances. Either tolerance ALONE may still be zero; that is how a caller asks for only the other one. Rejected HERE, not in callers. rainlang's `agree` word carried these checks while the library did not, which meant any other consumer calling `LibDecimalFloat.agree` directly — st0x.attest, or the next one — got no guard at all. A guard a caller can skip is not a guard, and moving the arithmetic into this library without the guard left the guard behind by accident. Three existing tests changed because the behaviour changed: - `testAgreeZeroSpread` passed 0/0 and now uses the smallest positive tolerance, so it still tests what it meant to. - `testAgreeAgainstIntegerOracle` can fuzz 0/0, so it nudges to a valid pair rather than discarding the run. - `testAgreeNeverReverts` asserted the opposite of the guard. Rescoped to `testAgreeNeverRevertsOnValues`: a valid tolerance, fuzzed values, which is the claim that was actually worth making — no pair of representable values can make the arithmetic revert. Added `testAgreeRejectsNegativeTolerance` (either side, both sides, and the case where the other term would have accepted the spread on its own, which is the one that used to pass silently), `testAgreeRejectsNoPositiveTolerance` (including zeros with non-zero exponents, since every representation of zero is treated alike), and `testAgreeAcceptsOneZeroTolerance` for the boundary between the two. The revert tests go through an external wrapper, because `agree` is an internal library call and its reverts otherwise land at the test's own call depth where `vm.expectRevert` cannot see them. 53 suites, 499 of 500. The one failure is `testSubPacked` reverting `ExponentUnderflow`, which is #271 and reproduces on main. Lint and fmt clean. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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ChangesAgree tolerance validation
Priority: ⬇️ Low Estimated code review effort: 2 (Simple) | ~10 minutes Change: Bug fix Merge Risk: ⚪ Minimal · up to The tolerance validation and its updated tests have no identified issue that needs resolution before merge. Architecture SummaryArchitecture risk: 🔵 Low · up to The change affects 2 systems. Changed systems: Architecture concerns Review detailsSystems and components
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In @test/src/lib/LibDecimalFloat.agree.t.sol:
- Around line 455-456: Update the `agreeExternal` assertion to use `Float.wrap`
values representing zeros with nonzero packed exponents, and use those same
values in both `expectRevert` and the call so the validation boundary is tested
without canonicalizing the inputs.
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src/error/ErrDecimalFloat.solsrc/lib/LibDecimalFloat.soltest/src/lib/LibDecimalFloat.agree.t.sol
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`packLossless` canonicalises every zero to `FLOAT_ZERO`, so `f(0, 5)` and `f(0, -5)` are the same word as `f(0, 0)`. The assertion claiming "every representation of zero is treated alike" therefore tested the canonical case a second time and said nothing about non-canonical zeros. Raised by CodeRabbit on #281 and confirmed: the new test asserts that premise explicitly, so it cannot rot back. Non-canonical zeros are now built with `Float.wrap` — the exponent is the high 32 bits, so a zero coefficient at exponent 5 and at exponent -5 are distinct words that are both numerically zero — and checked alone, and mixed with a canonical zero either way round. Four tests added around the guard: - `testAgreeRejectsNonCanonicalZeroTolerances`, with the premise assertions above, which is what makes the guard demonstrably numeric rather than bytewise. - `testAgreeAcceptsNonCanonicalZeroWithPositive`. Without it the test above also passes for a guard that wrongly rejected ANY non-canonical tolerance, so this is what makes the rejection specifically about having no tolerance. - `testAgreeGuardHoldsForArbitraryTolerances`: the guard as a law over arbitrary packed pairs, 5000 runs. The expectation comes from the tolerances' own signs via `lt`/`gt` against zero rather than from calling `agree`, so it pins the guard's domain instead of restating its implementation. Values are held fixed and valid so the tolerance pair is the only variable. - `testAgreeRejectsBadToleranceAtTheRangeExtremes`: rejection holds where the spread is the widest representable. 33 in the agree suite, up from 29. 53 suites, 503 of 504; the failure is #271 and reproduces on main. Lint and fmt clean. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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agreeaccepted a negative tolerance, and accepted a pair with no positivetolerance, leaving both to callers. Both are now rejected in
agree.Why these are not caller concerns
A negative tolerance cannot mean anything. The spread is a distance, so it
is non-negative:
spread <= negativeis unsatisfiable on its own, and under themaxthe negative term is inert — it cannot cancel the other term, only fail tobe it. It is representable solely because floats are signed. Accepting it meant a
closeness check built on a malformed tolerance quietly passed on the other term.
Neither tolerance positive is a tolerance of nothing. The limit is zero and
agreedegenerates into exact equality, whicheqanswers directly and morecheaply. A caller that meant to set a tolerance and set none was being
misunderstood rather than served.
Either tolerance alone may still be zero. That is how a caller asks for only
the other one, and it is what makes the second rejection about having no
tolerance rather than about zero appearing at all.
Why in the library
rainlang's
agreeword carried these checks while this library did not. So anyother consumer calling
LibDecimalFloat.agreedirectly — st0x.attest, or thenext one — got no guard at all. A guard a caller can skip is not a guard.
This is a defect I introduced in #278: moving the arithmetic out of the word and
into the library left the guard behind, and the natspec I wrote ("the caller is
responsible for the tolerances being sensible") made the omission read as
intent. It was not intent, and I said #278 was ready for external audit while it
stood.
Errors
AgreeToleranceNegative(absolute, proportional)andAgreeNoPositiveTolerance(absolute, proportional), both carrying the offendingtolerances, documented with what a silent alternative would do — matching how
the rest of
ErrDecimalFloat.soljustifies its reverts.QA
testAgreeRejectsNegativeToleranceandtestAgreeRejectsNoPositiveToleranceboth fail on base, where the callsreturn instead of reverting. They discriminate rather than merely exercise:
the negative case includes a pair where the other term would have accepted
the spread on its own, which is precisely the input that used to pass silently
and which a guard placed after the arithmetic would still let through; and it
covers a negative on either side and on both. The no-positive case includes
zeros with non-zero exponents, so a guard written against the raw bytes rather
than the numeric value would fail it.
testAgreeAcceptsOneZeroTolerancepinsthe boundary, so a guard that over-rejected any zero would fail.
mutants.tomlstillpass and cover the arithmetic. The guard's own mutants are the two comparison
directions and the
&&/||in the positive test — each is killed by the testsabove by construction, since flipping either comparison turns a rejected input
into an accepted one and the tests assert the exact selector and arguments. I
have not run the probe on them, so I am not claiming a score.
|highest - lowest|and so non-negative, which makes a negative limit unsatisfiable bydefinition; and with both terms zero the limit is zero, which is exact
equality by definition. Neither expectation is read back from output. The
errors carry the tolerances, so the assertions check the reported values as
well as the fact of the revert.
agreeaccepts tolerances that cannotmean anything". Covered: negative on either side and both, and no-positive
including alternate zero representations. The arithmetic is untouched — the
guard runs before it and returns the same answers for every valid tolerance,
which the 27 pre-existing agree tests establish by passing unchanged except
where the behaviour genuinely changed.
Tests that changed because the behaviour changed
testAgreeZeroSpreadpassed0/0; now uses the smallest positive tolerance,so it still tests what it meant to.
testAgreeAgainstIntegerOraclecan fuzz0/0; nudges to a valid pair ratherthan discarding the run.
testAgreeNeverRevertsasserted the opposite of the guard. Rescoped totestAgreeNeverRevertsOnValues— a valid tolerance with fuzzed values, whichis the claim worth making: no pair of representable values can make the
arithmetic revert.
The revert tests go through an external wrapper, since
agreeisinternalandits reverts otherwise land at the test's own call depth where
vm.expectRevertcannot see them.
Verification
53 suites, 499 of 500. The one failure is
testSubPackedrevertingExponentUnderflow— #271, reproduces onmain, untouched here.forge lint -D warningsandforge fmt --checkboth exit 0.Follow-up
rainlang #592 currently validates in the word. Once this releases, that branch
bumps and drops
validateTolerancesandagreedAt, leavingrunandreferenceFncallingLibDecimalFloat.agreedirectly.🤖 Generated with Claude Code
Summary by CodeRabbit
agreecheck rejects negative tolerances and cases where both tolerances are zero, with errors reporting the supplied values.