core: Check whether zero uncles check in verifyUncles is redundant

[kevaundray]

Pulling this out from comment thread here

[kevaundray]

@rjl493456442 Since Test (1.24) passes*, I believe it shows that the check is not needed in ValidateBody. I also ran a unit test locally to check this (that VerifyHeader catches the empty uncle hash and validateBody checks that they match).

Would delegate to you as to how you think we should handle this.

*appveyor fails on master, so I'm assuming we can just ignore it

[gballet]

Just checked the coverage and it turns out that this file has 0% coverage 🤯 so just passing the tests isn't enough.

[kevaundray]

Just checked the coverage and it turns out that this file has 0% coverage 🤯 so just passing the tests isn't enough.

I had assumed that this would be tested via EEST, though I also asked claude to make a test case locally while CI was working:

func TestPostMergeUncleRejection(t *testing.T) {
	// Generate a small post-merge chain
	gspec := &Genesis{Config: params.TestChainConfig}
	engine := beacon.New(ethash.NewFaker())
	_, blocks, _ := GenerateChainWithGenesis(gspec, engine, 2, func(i int, gen *BlockGen) {
		gen.SetPoS()
	})

	options := DefaultConfig().WithStateScheme(rawdb.HashScheme)
	chain, err := NewBlockChain(rawdb.NewMemoryDatabase(), gspec, engine, options)
	if err != nil {
		t.Fatal(err)
	}
	defer chain.Stop()

	// Insert the first block so we have a parent
	if _, err := chain.InsertChain(blocks[:1]); err != nil {
		t.Fatal(err)
	}
	goodBlock := blocks[1]
	uncle := &types.Header{
		ParentHash: blocks[0].Hash(),
		Number:     big.NewInt(2),
		Time:       goodBlock.Time(),
	}
	bodyWithUncle := types.Body{
		Transactions: goodBlock.Transactions(),
		Uncles:       []*types.Header{uncle},
		Withdrawals:  goodBlock.Withdrawals(),
	}

	// Case 1: Header with non-empty uncle hash.
	// VerifyHeader should reject because UncleHash != EmptyUncleHash post-merge.
	badHeader := *goodBlock.Header()
	badHeader.UncleHash = types.CalcUncleHash(bodyWithUncle.Uncles)
	if err := engine.VerifyHeader(chain, &badHeader); err == nil {
		t.Error("VerifyHeader accepted post-merge block with non-empty uncle hash")
	}

	// Case 2: Block with uncles in body BUT EmptyUncleHash in header (dishonest header).
	// ValidateBody should reject because CalcUncleHash(uncles) != header.UncleHash.
	dishonestBadBlock := goodBlock.WithBody(bodyWithUncle)
	if dishonestBadBlock.Header().UncleHash != types.EmptyUncleHash {
		t.Fatal("test setup: expected EmptyUncleHash in dishonest block header")
	}
	if err := chain.validator.ValidateBody(dishonestBadBlock); err == nil {
		t.Error("ValidateBody accepted post-merge block with uncles in body but EmptyUncleHash in header")
	}
}

Then played around with the code to ensure I wasn't missing anything

[kevaundray]

Closing alongside #34007