René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"No type inferrence of callback arguments inside a tuple union type","articleBody":"### 🔎 Search Terms\n\n- discriminated union inference \r\n- union argument inference \n\n### 🕗 Version \u0026 Regression Information\n\n- This is a compilation error in `tsserver 3.3.2`                                                                  \n\n### ⏯ Playground Link\n\nhttps://www.typescriptlang.org/play?#code/C4TwDgpgBAkgdgMwgJwILIOZQLwCgpQA+UA2gIwA0UAFAIYBcUcArgLYBGKAlDgHxQA3APYBLACYBdfEVIAmKtXaMAzsGQi4GHtn7DxEgNy4AxkLiqotTI3hI0mHKUo1a2-gG8oAX0O4gA\n\n### 💻 Code\n\n```ts\r\ntype InferArg =\r\n  | [1, (a: number) =\u003e void]\r\n  | [2, (b: string) =\u003e void];\r\nconst arg: InferArg = [1, (a) =\u003e { }];\r\n```\r\n\n\n### 🙁 Actual behavior\n\nI get a compilation error:\r\n\u003e Parameter 'a' implicitly has an 'any' type.(7006)\n\n### 🙂 Expected behavior\n\n`a` should be inferred to be a `number` because I already passed `1` as the first tuple element. Type inference should be identical to this code:\r\n```ts\r\ntype InferArg = [1, (a: number) =\u003e void];\r\nconst arg: InferArg = [1, (a) =\u003e { }];\r\n```\n\n### Additional information about the issue\n\n_No response_","author":{"url":"https://github.com/nenikitov","@type":"Person","name":"nenikitov"},"datePublished":"2023-09-05T00:38:00.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/55632/TypeScript/issues/55632"}