[devin-ai-integration]

What and why

The 0.11.0 performance record (measured against v0.10.1) finds the language server's ReferencesCold at 44.5k → 6.28M allocs/op and RenameWarm at 14.9k → 12.4M. Bisected over the pull-request merges to #1062 (hidden colliding imports, 45k → 17.4M), later cut to 6.28M by #1158 and #1209. The allocation profile puts three quarters of what is left in Resolver.namespaceChildren, which for every index entry under an imported namespace:

• built the entry's qualified name with Index.GetFQN to decide whether it is a re-export (reexportedUnder);
• for a re-export, allocated a one-candidate slice per name it binds and handed it to withoutHiddenImports, which answered from the memoized hidesBelow that nothing on the route is hidden (hiddenOnRoute);
• copied the route conditions gating the name into a [][]ElementFilter through Index.ReexportGates, which admitsUnderName then read once, accepting the first unfiltered route (gateRoutes).

This change keeps the decisions and drops the allocations: hiddenOnRoute asks hidesBelow first; reexportedUnder compares the owner chain against the prefix segment by segment with the new symbols.FQNIs; admitsUnderName walks the routes in place through the new Index.EachReexportGate (ReexportGates stays for its other caller and gateRoutes returns nil when no route qualifies). ReferencesWarm, WorkspaceUpdate and FormatEdits are unchanged.

What this does not recover: both rows still allocate about 1 GiB/op and take over a second, against 49 ms and 23 ms before #1062. The space profile puts that in elementList.add: each query re-enumerates the members every wildcard import brings (importedMembersInto, whose per-edge memo enumMembers is cleared when the outermost enumeration returns), per occurrence in ImportedBeside for a rename and per document for the references index, and the enumeration itself is what #1062 made expensive. Keeping that enumeration across a query is a design change in the same code the in-flight perf/name-first-recursive-import-matching branch reworks, so it is left to a follow-up rather than done here.

How it was verified

• TestImportedMemberEnumerationDoesNotWalkRoutesPerMember (internal/semantic/resolve): a differential testing.AllocsPerRun bound — enumerating a member re-exported through a second wildcard import (R imports Q::*, Q imports L::*; namespaces of 2n and n members, per member) costs at most 3 allocations. On develop before this change it costs 6.23 and the test fails; with it 2.23.

• TestFQNIsMatchesFQNOf and TestEachReexportGateWalksReexportGates (internal/semantic/symbols): the new helpers answer as FQNOf and ReexportGates do, stop at the first accepting visit, and allocate nothing.

• Benchmark A/B, six interleaved rounds on the record's machine, pre-regression commit 0af9fcb36 (the parent of the fix(resolve): hide imported memberships that collide by name #1062 merge) in a scratch worktree | develop b60a18c20 | this branch:

  row	allocs/op	B/op	sec/op
  ReferencesCold	44.5k | 6 279k | 1 945k	9.7 MiB | 1 010 MiB | 950 MiB	49 ms | 1 970 ms | 1 383 ms
  RenameWarm	14.9k | 12 410k | 3 740k	1.4 MiB | 1 668 MiB | 1 549 MiB	23 ms | 2 904 ms | 1 928 ms
  ReferencesWarm	1 017 | 1 017 | 1 017	339 KiB all	within noise
  WorkspaceUpdate	710.6k all	57.2 MiB all	within noise

• go test ./internal/semantic/... ./internal/frontend/lsp ./internal/workspace/... ./tests/resolve ./internal/check/... pass (the two failures without the pilot and training corpora present pass with them), go build ./..., go vet on the touched packages, gofmt -l . empty, python3 scripts/changelog.py check.

Checklist

• make test and make lint pass locally (the packages above; the full suite runs in CI)
• Tests added or updated for the change
• Documentation extended where it already covers the surface (no user-facing surface changes)
• Changelog entry added as changes/unreleased/<slug>.<section>.md, not as an edit to CHANGELOG.md
• baselines regenerated and make docs-counts run if a gate count moved (none moved)
• No internal work-item labels (waves, slices, F4, K5) in the body, docs, or changelog

Link to Devin session: https://nasa-jpl-demo.devinenterprise.com/sessions/cf22d7a746814d20b2f0eaf11682fef9
Open in Devin Desktop: https://nasa-jpl-demo.devinenterprise.com/desktop/session/cf22d7a746814d20b2f0eaf11682fef9?variant=devin
Requested by: @HuiJun

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring