syntax_data: {"ast_node_type":"variable","tokens":[{"end":82,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                         let upvars = self.capture_upvar(expr, captured_place, ty);
context_before:                     .map(|(captured_place, ty)| {
context_after:                         self.thir.exprs.push(upvars)