{"author_url":"https://blog.hatena.ne.jp/susisu/","width":"100%","blog_title":"Object.create(null)","title":"Optional Variance Annotations \u306e\u6319\u52d5\u30e1\u30e2","provider_name":"Hatena Blog","author_name":"susisu","height":"190","description":"TypeScript 4.7 \u306e optional variance annotations \u306e\u6319\u52d5\u3092\u82e5\u5e72\u52d8\u9055\u3044\u3057\u3066\u3044\u305f\u306e\u3067\u30e1\u30e2. \u4f8b 1 (Playground): type Extends<A, B> = A extends B ? true : false; type Bivariant<T> = {}; type Bivariant_A0 = Extends<Bivariant<\"foo\">, Bivariant<\"foo\" | \"bar\">>; // true type Bivariant_A1 = Extends<Bivariant<\"foo\" | \"bar\">, Bivarian\u2026","version":"1.0","blog_url":"https://susisu.hatenablog.com/","provider_url":"https://hatena.blog","image_url":null,"url":"https://susisu.hatenablog.com/entry/2022/06/02/024923","html":"<iframe src=\"https://hatenablog-parts.com/embed?url=https%3A%2F%2Fsusisu.hatenablog.com%2Fentry%2F2022%2F06%2F02%2F024923\" title=\"Optional Variance Annotations \u306e\u6319\u52d5\u30e1\u30e2 - Object.create(null)\" class=\"embed-card embed-blogcard\" scrolling=\"no\" frameborder=\"0\" style=\"display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;\"></iframe>","categories":["\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0","TypeScript","\u5c0f\u30cd\u30bf"],"published":"2022-06-02 02:49:23","type":"rich"}