syntax_data: {"ast_node_type":"variable","tokens":[{"end":67,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let id = BlockMarkerId::from_usize(self.num_block_markers);
context_before:     fn next_block_marker_id(&mut self) -> BlockMarkerId {
context_after:         self.num_block_markers += 1;