syntax_data: {"ast_node_type":"variable","tokens":[{"end":47,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let borrow_kind = match mutbl {
context_before:                 // expr = &mut target
context_after:                     hir::Mutability::Mut => BorrowKind::Mut { kind: mir::MutBorrowKind::Default },