René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Type inference regression on function calls not saved to variables, due to #61668","articleBody":"### 🔎 Search Terms\n\n61668 inference overload regression tuple\n\n### 🕗 Version \u0026 Regression Information\n\n- This changed in commit or PR #61668\n\n\n### ⏯ Playground Link\n\nhttps://www.typescriptlang.org/play/?ts=5.9.0-beta#code/PTAEGIDYEZMgOUBjAFgQwHYHMCmBnUAFxR1AEsMAzHAJxwyVMpoHsBbUAbQwFc2AjWgBpQeQjQpYAukRagAFLwG0APmInYAlJykAoACY4kAGzR1QlHg0JkWGULkIA5PvM0AuUAAVWbMnhwAHiVBGgA+AG4DI1NzS2tbe0cAZXE3Tx92fyD1SUjokzMmKyQbO1AeAIAVHgAHYxx5QjqGz24+UJFc7CkPUAA3FjJ9KKQ7MVBa0ABeb19sgDo6PBZjfsadTQXienk3GbC5rICFtGNjeU5HFzY3ERS0zV6tnYx5Spwa+pxNKKA\n\n### 💻 Code\n\n```ts\ndeclare function getNum(): Promise\u003cnumber\u003e;\ndeclare function getStr(): Promise\u003cstring\u003e;\ndeclare function useTuple(tuple: [number, string]): void;\nconst p = Promise.resolve([]).then(() =\u003e Promise.all([getNum(), getStr()])).then(useTuple);\n```\n\n\n### 🙁 Actual behavior\n\nThe `Promise.all` infers to `Promise\u003c(number|string)[]\u003e`.\n\n### 🙂 Expected behavior\n\nThe `Promise.all` should infer `Promise\u003c[number, string]\u003e`.\n\n### Additional information about the issue\n\nThis only happens when the `Promise.all` call is directly returned.  If I instead write\n\n```\nconst p = Promise.all([getNum(), getStr()]);\nreturn p;\n```\n\nthen it infers the tuple correctly again, even without doing anything that would suggest it should infer the type differently.\n\nThis PR also impacted inference of enums: in [another example](https://www.typescriptlang.org/play/?ts=5.9.0-beta#code/PTAEDkHkBUFEC5QHsBGBnApgJwG7baAJYEDGSAdgC5YCGONWhNVAUCQDY1oEDKArigBWGEpQA80AHygA3i1DJ02PFjSIAFOvrs+GRNACUoALzScSQgBMDAbQC6J0PYDc80GXJpqfUUizqAB0Z6SgxQAH1tXX0jGQBfFgSWDHI+AFtQAFkkSzC5BQBBRwByGmKAGjcAIRKUCsSWNk5uUB5lQhI8tzScjABCRH4hEXFs3MlXBNyOBjCAMz5yUUIKdywMGlDskgBrMUghSUCsJAC1WRsABSJyUB2MAE8kOdADwTsAfkQ3q7s4g0Q5isrjY602GG2ezauA6GCO+VAIAgMAQoGgAAtiDc5tgUp13OjmABzDCWG6gADEADYAIxUqkADm6vUQ5AwAHdWgJhKJ1GMMAA6AoGSr-EEeLygHq5RxszlDHmUPm9IUGVxIhSgAB6H1BGy2SF2YmhOFh8OlGDFLCAA), I pass `{mode: new Subject(Mode.A)}` into a function that fails because it infers `Subject\u003cMode.A\u003e` while if I save a temporary `const mode = new Subject(Mode.A);` then it infers `Subject\u003cMode\u003e` and passes.","author":{"url":"https://github.com/shicks","@type":"Person","name":"shicks"},"datePublished":"2025-07-15T04:53:56.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/62071/TypeScript/issues/62071"}