`LockAnnotation lock(::cs_main)` is a guarantee to the compiler thread analysis that `::cs_main` is locked (when it couldn't be determined otherwise).

Despite being annotated with the locking guarantee ...

https://github.com/bitcoin/bitcoin/blob/65526fc8666fef35ef908dbc225f706bef642c7e/src/interfaces/chain.cpp#L134-L138

... `getTipLocator()` reads `chainActive` (via `::ChainActive()`) without holding `cs_main`.

This can be verified by adding the following `AssertLockHeld(cs_main)`:

```
$ git diff
diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index 59623284d..9fc693a0f 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -134,6 +134,7 @@ class LockImpl : public Chain::Lock
     CBlockLocator getTipLocator() override
     {
         LockAnnotation lock(::cs_main);
+        AssertLockHeld(::cs_main);
         return ::ChainActive().GetLocator();
     }
     Optional<int> findLocatorFork(const CBlockLocator& locator) override
$ make check
../build-aux/test-driver: line 107: 12881 Aborted                 "$@" > $log_file 2>&1
FAIL: qt/test/test_bitcoin-qt
```
nMinOrderPos = wtx->nOrderPos;
            copyFrom = wtx;
        }
    }
    if (!copyFrom) {
        return;
    }
    
    for (TxSpends::iterator it = range.first; it != range.second; ++it)
    {
        const uint256& hash = it->second;
        CWalletTx* copyTo = &mapWallet.at(hash);
        if (copyFrom == copyTo) continue;
        assert(copyFrom && "Oldest wallet transaction in range assumed to have been found.");
        if (!copyFrom->IsEquivalentTo(*copyTo)) continue;
        copyTo->mapValue = copyFrom->mapValue;
        copyTo->vOrderForm = copyFrom->vOrderForm;
        
        
        copyTo->nTimeSmart = copyFrom->nTimeSmart;
        copyTo->fFromMe = copyFrom->fFromMe;
        
        
    }
}
/**
 * Outpoint is spent if any non-conflicted transaction
 * spends it:
 */
bool CWallet::IsSpent(interfaces::Chain::Lock& locked_chain, const uint256& hash, unsigned int n) const