Function checkAsyncKeyword

docs/scripts/ajv-validator.js:3374–3377

({ schemaEnv }, def)

                }, () => cxt.error());
            }
            function checkAsyncKeyword({ schemaEnv }, def) {
                if (def.async && !schemaEnv.$async)
                    throw new Error("async keyword in sync schema");
            }
            function useKeyword(gen, keyword, result) {
                if (result === undefined)
                    throw new Error(`keyword "${keyword}" failed to compile`);