Ground keccak chains for nested reference heads

[halaprix]

The defect

A mapping, dynamic array or bytes/string declared inside a struct or an
array element could not be named at all. Every access to one resolved as
unresolved — the product silently failed to name storage it otherwise
understands perfectly.

buildStaticIndex built variableBaseSlots from layout.storage
(packages/semantics/src/resolve.ts:60-63), which lists top-level entries
only. For struct Nested { uint256 head; mapping(address => uint256) inner; }
the layout entry is nest; the mapping member is not there. So
referenceVariablesBySlot (chains.ts:31) never saw the head,
groundHash could not ground keccak(key ‖ headSlot), and the chain died.

This was found while planning slotscope-xu8 (v1.4). The first diagnosis was
that a nested head merely lost its display name; it is worse than that — the
resolution never happens.

The fix

buildStaticIndex already decodes the layout to populate cellsBySlot, and that
model carries every nested head as a CollapsedStorageSpan with its exact base
slot, its dotted path (nest.inner, pairs[1].m) and — since #4 — the solc
encoding. Index those spans too. Eight lines, no new traversal, no new source of
truth.

Two consumers get the same repair for free, because both look variables up in
that index: string/bytes migration annotation (resolve.ts:226) and the
bytes-data chunk labels (chains.ts:277). Nested bytes/string heads now
annotate correctly as well.

Verification

The new test in chains.test.ts compiles and executes a real contract rather
than asserting against a hand-built layout, and was confirmed failing first
(expected 'unresolved' to be 'exact'). A write to nest.inner[addr] now
resolves exact as nest.inner[0xaa…] with its value decoded.

Gate	Result
format:check, lint, typecheck	clean
test:unit	236/236, including the Forge cross-check
test:e2e	61/61
fixtures:verify	no drift
release:verify	passed

Closes slotscope-02a. Unblocks slotscope-xu8 (v1.4), which needs naming
settled before its UI work.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
slotscope	Ready	Preview	Jul 30, 2026 2:35pm