private void FetchFlowEntry()
{
// Reset any potential simple keys on the current flow level.
RemoveSimpleKey();
// Simple keys are allowed after ','.
simpleKeyAllowed = true;
// Consume the token.
var start = cursor.Mark();
Skip();
// Create the FLOW-ENTRY token and append it to the queue.
tokens.Enqueue(new FlowEntry(start, cursor.Mark()));
}