{"ast_node_type":"variable","tokens":[{"end":82,"kind":"keyword","start":0,"text":"let"}]}
    let requires = SyntaxExtensionKind::Attr(Arc::new(contracts::ExpandRequires));
    register(sym::quote, SyntaxExtensionKind::Bang(Arc::new(BangProcMacro { client })));
    register(sym::contracts_requires, requires);