syntax_data: {"ast_node_type":"variable","tokens":[{"end":58,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let dfa = alts.next().ok_or(Uninhabited)?;
context_before:                 // If there are no alternatives, return `Uninhabited`.
context_after:                 // Combine the remaining alternatives with `dfa`.