{"ast_node_type":"variable","tokens":[{"end":87,"kind":"keyword","start":0,"text":"let"}]}
    let width = ctx.expr_field(Ident::new(sym::width, sp), ctx.arena.alloc(width), sp);
    let precision = ctx.expr_field(Ident::new(sym::precision, sp), ctx.arena.alloc(precision), sp);
    let placeholder = ctx.arena.alloc(hir::QPath::LangItem(hir::LangItem::FormatPlaceholder, sp));