syntax_data: {"ast_node_type":"variable","tokens":[{"end":59,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let cast_kind = mir_cast_kind(ty, expr.ty);
context_before:                 debug!("ExprKind::Cast from_ty={from_ty:?}, cast_ty={:?}/{cast_ty:?}", expr.ty);
context_after:                 block.and(Rvalue::Cast(cast_kind, source, expr.ty))