syntax_data: {"ast_node_type":"variable","tokens":[{"end":54,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let borrow_kind = match upvar_borrow {
context_before:             ty::UpvarCapture::ByRef(upvar_borrow) => {
context_after:                     ty::BorrowKind::Immutable => BorrowKind::Shared,