René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"\u003ckey\u003e is referenced directly or indirectly in its own type annotation","articleBody":"**TypeScript Version:** 2.8.0-dev.20180217\r\n\r\n**Search Terms:**\r\n- \"is referenced directly or indirectly in its own type annotation\"\r\n\r\n**Code**\r\n\r\n```ts\r\ntype Flatten\u003cT\u003e = {\r\n  '1': Flatten\u003cT extends Array\u003cinfer U\u003e ? U : T\u003e;\r\n}[T extends number ? '1' : '1'];\r\n```\r\n(as mentioned in #21613)\r\n\r\n**Expected behavior:** ok\r\n\r\n**Actual behavior:**\r\n\r\n\u003e error TS2502: ''1'' is referenced directly or indirectly in its own type annotation.\r\n\r\n**Playground Link:** needs 2.8, playground is on 2.7\r\n\r\n**Related Issues:** #6230\r\n\r\nI saw similar issues on other types, though the greatest common denominator appeared to be recursion + conditional types (?).\r\n","author":{"url":"https://github.com/KiaraGrouwstra","@type":"Person","name":"KiaraGrouwstra"},"datePublished":"2018-02-17T23:50:31.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/22018/TypeScript/issues/22018"}