René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Lift Template Literal Restriction on Backslashes","articleBody":"# Overview\r\n\r\nEveryone loves L\u003csup\u003eA\u003c/sup\u003eT\u003csub\u003eE\u003c/sub\u003eX so ESNext will likely allow tagged template strings to contain backslashes on any sequence - even ones that look like they might contain an invalid Unicode escapes.\r\n\r\nIn other words, something like\r\n\r\n```ts\r\nlet x = tag `\\u{wat}`;\r\n```\r\n\r\nis now valid, whereas previously it would be considered an error.\r\n\r\nReference: https://tc39.github.io/proposal-template-literal-revision/\r\n\r\nAs of this writing, the linked proposal is at Stage 3.\r\n\r\n# Notes\r\n\r\n1. This restriction lift doesn't apply to *untagged* template strings. For example:\r\n\r\n   ```ts\r\n   // All of these are still invalid.\r\n   let bad = `bad escape sequence: \\unicode`;\r\n   let bracingOurselves = `\\u{shouldntDoThis}`;\r\n   let theWorst = `\\xtremely bad`;\r\n   ```\r\n\r\n2. Because there is no appropriate representation for a \"cooked\" string that contains one of these escapes, the returned value at a position on the top-level array will be `undefined`, but the raw representation will be available. For example:\r\n\r\n   ```ts\r\n   function tag(strs) {\r\n     console.log(strs[0] === undefined);\r\n     console.log(strs.raw[0] === \"\\\\unicode and \\\\u{55}\");\r\n   }\r\n  // Prints 'true' twice.\r\n   tag`\\unicode and \\u{55}`\r\n\r\n# Proposed Emit\r\n\r\nInput:\r\n\r\n```ts\r\nlet x = tag `\\u{hello} ${ 100 } \\xtraordinary ${ 200 } wonderful ${ 300 } \\uworld`;\r\n```\r\n\r\nOutput:\r\n\r\n```js\r\nvar x = (\r\n    _a = [undefined, undefined, \" wonderful \", undefined],\r\n    _a.raw = [\"\\\\u{hello} \", \" \\\\xtraordinary \", \" wonderful \", \" \\\\uworld\"],\r\n    tag(_a, 100, 200, 300)\r\n);\r\n```","author":{"url":"https://github.com/DanielRosenwasser","@type":"Person","name":"DanielRosenwasser"},"datePublished":"2016-12-06T23:56:42.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":11},"url":"https://github.com/12700/TypeScript/issues/12700"}