When using triple slash references, the tag must contain a path, types,
lib, or no-default-lib key. If the tag does not include any of these keys,
this error will be reported:
/// <reference />Fix: Use a valid reference directive.
To fix the error, complete the tag by adding a valid key:
/// <reference path="./some-file" />
/// <reference types="node" />
/// <reference lib="es2015" />
/// <reference no-default-lib="true"/>Also see Triple-Slash Directives in the TypeScript Handbook.