Re-verified from primary sources:
- THE DEEP CHECK: the three discharged u32 Step defs vs the PINNED
rustc's own library/core/src/iter/range.rs (nightly-2026-06-01,
u32 = narrower arm on 64-bit): forward/backward = try_from-then-
checked_{add,sub} (try_from succeeds iff n < 2^32), steps_between =
(0, None) iff start > end else saturated diff twice. Branch-for-
branch identical to the defs in FunsExternal.lean.
- commit scopes: bde63f5 = exactly the 3 axiom->def swaps; d6e4d93 =
only the new draft file.
- fresh audits: the u32 Step INSTANCE and each of the three defs are
axiom-clean ([propext(, Classical.choice, Quot.sound)]); check.sh
green fresh; draft compiles with exactly ONE sorry (line 65, succ
branch); base case genuinely closed.
- the 'dalek u32 Step axioms are vestigial' claim: confirmed — every
IteratorRange.next call site in dalek's gen uses StepUsize.
- remote heads match local everywhere.
Drill catch (documentation, not error): the loop increments the index
BEFORE each oracle call (forward_checked inside next, .panic on
overflow), the fold AFTER (add's overflow error) — equal only under
the theorem's start.val + s < 2^32 precondition, which is exactly why
that precondition exists. Now documented on chainFoldN so the
step-case prover discharges both increments from the bound and nobody
weakens it.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
mrwulf
ce2d38832c