{"ast_node_type":"variable","tokens":[{"end":80,"kind":"keyword","start":0,"text":"let"}]}
    let fields = ctx.arena.alloc_from_iter([position, flags, precision, width]);
    let placeholder = ctx.arena.alloc(hir::QPath::LangItem(hir::LangItem::FormatPlaceholder, sp));
    ctx.expr(sp, hir::ExprKind::Struct(placeholder, fields, hir::StructTailExpr::None))