fix(beacon-node): apply tsgo cast + add slot to merged-in #9479 test emit

[lodekeeper]

Summary

The base-branch update brought in #9479's new test ("defers envelope validation until the block is in fork choice when payload input is seeded from the block body") which uses the same let emitter!: ChainEventEmitter + destructuring-assignment + sibling closure capture pattern that #9491 already mitigated in the original failing test below. Same TS2769 fires at the new test's emit site:

test/unit/sync/unknownBlock.test.ts(1027,20): error TS2769: No overload matches this call.
  Argument of type 'ChainEvent.unknownEnvelopeBlockRoot' is not assignable to parameter of type 'unique symbol'.

Also, #9479's emit predates this PR's addition of slot: Slot to the ChainEvent.unknownEnvelopeBlockRoot event signature, so the emit data is missing the required slot field after the merge.

Fix

Same minimal cast workaround as #9491 plus the required slot: 0 field:

-      emitter.emit(ChainEvent.unknownEnvelopeBlockRoot, {
+      // tsgo overload-resolution miss when emit is reached through a closure that captures emitter
+      // first; cast re-anchors the StrictEventEmitter overload for ChainEvent keys (see #9491).
+      (emitter as ChainEventEmitter).emit(ChainEvent.unknownEnvelopeBlockRoot, {
         rootHex: blockRootHex,
+        slot: 0,
         peer,
         source: BlockInputSource.gossip,
       });

Single-site change. The 5 other emitter.emit(ChainEvent.unknownEnvelopeBlockRoot, ...) sites in the file remain unchanged because they aren't reached through a sibling closure capture; the cast at the sibling test's emit (introduced in #9491, currently at line 1126) also remains as-is and continues to typecheck cleanly with the expanded EventType union from #9439.

Test plan

• CI: Type Checks (24) passes (no TS2769 on unknownBlock.test.ts).
• CI: the new defers envelope validation until the block is in fork choice when payload input is seeded from the block body test still passes — emit semantics unchanged.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request updates a unit test in unknownBlock.test.ts by casting emitter to ChainEventEmitter to resolve a TypeScript overload-resolution issue and adding a slot property to the emitted event payload. The reviewer suggested fixing a typo in the added comment (tsgo to tsc) and replacing the hardcoded slot: 0 with block.message.slot for better accuracy and robustness.

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[gemini-code-assist]

There is a typo in the comment (tsgo instead of tsc). Additionally, instead of hardcoding slot: 0, it is more accurate and robust to use block.message.slot to match the slot of the block and envelope created in the test fixture.

Suggested change

	// tsgo overload-resolution miss when emit is reached through a closure that captures emitter
	// first; cast re-anchors the StrictEventEmitter overload for ChainEvent keys (see #9491).
	(emitter as ChainEventEmitter).emit(ChainEvent.unknownEnvelopeBlockRoot, {
	rootHex: blockRootHex,
	slot: 0,
	peer,
	source: BlockInputSource.gossip,
	});
	// tsc overload-resolution miss when emit is reached through a closure that captures emitter
	// first; cast re-anchors the StrictEventEmitter overload for ChainEvent keys (see #9491).
	(emitter as ChainEventEmitter).emit(ChainEvent.unknownEnvelopeBlockRoot, {
	rootHex: blockRootHex,
	slot: block.message.slot,
	peer,
	source: BlockInputSource.gossip,
	});

[lodekeeper]

Declining both suggestions, but flagging the reasoning:

1. tsgo vs tsc — tsgo is correct, not a typo. This repo uses @typescript/native-preview via "check-types": "tsgo" in packages/beacon-node/package.json:94, with @typescript/native-preview: 7.0.0-dev.20260303.1 pinned in the root package.json. The overload-resolution behavior that motivates this cast is specifically tsgo's — tsc doesn't reject this site.

2. slot: 0 vs block.message.slot — kept slot: 0 for consistency with every other emitter.emit(ChainEvent.unknownEnvelopeBlockRoot, ...) site in this file (unknownBlock.test.ts:762, :836, :926, :1131). The field is a logging/prune hint per the emitter.ts comment (// slot is the message slot, not necessarily the envelope's slot, but useful as a logging/prune hint), not a correctness-load-bearing value in these tests, and switching just this one site would diverge from the established pattern. Happy to update all sites to block.message.slot in a follow-up if you'd rather have semantic accuracy across the board.

[lodekeeper]

Re Gemini's two suggestions on the inline thread: declined both with reasoning in discussion_r3381092996. tldr: tsgo is correct (this repo uses @typescript/native-preview via "check-types": "tsgo", the overload-resolution behavior is tsgo-specific), and slot: 0 matches the established convention across every other emitter.emit(ChainEvent.unknownEnvelopeBlockRoot, ...) site in this test file. Noted on the consumer-version sunset.