syntax_data: {"ast_node_type":"other","tokens":[{"end":40,"kind":"keyword","start":0,"text":"for"}]}
source_snippet:             for upvar in upvars.iter() {
context_before:             print_indented!(self, "upvars: [", depth_lvl + 1);
context_after:                 self.print_expr(*upvar, depth_lvl + 2);