syntax_data: {"ast_node_type":"other","tokens":[{"end":78,"kind":"keyword","start":0,"text":"assert!(bpos.to_u32()"}]}
source_snippet:                 assert!(bpos.to_u32() >= mbc.pos.to_u32() + mbc.bytes as u32);
context_before:                 // character.
context_after:             } else {