TypeScript - guide with Type Inference in a Recursive Function for Flattening Nested Arrays
Hey everyone, I'm running into an issue that's driving me crazy. I'm a bit lost with This might be a silly question, but I'm working through a tutorial and I'm deploying to production and Quick question that's been bugging me - I'm trying to implement a recursive function in TypeScript to flatten a nested array of numbers or arrays....... However, I'm running into issues with type inference, specifically when applying the recursive call. My goal is to ensure that the function can handle multiple levels of nesting while maintaining type safety. I've defined the function like this: ```typescript function flatten<T>(arr: (T | T[])[]): T[] { const result: T[] = []; for (const item of arr) { if (Array.isArray(item)) { result.push(...flatten(item)); // Type inference scenario here } else { result.push(item); } } return result; } ``` When I try to call this function with a nested array, such as `flatten([1, [2, [3, 4]], 5])`, I expect it to return `[1, 2, 3, 4, 5]`. Instead, I'm getting the following behavior: ``` Argument of type 'T[]' is not assignable to parameter of type 'never[]'. ``` I tried adding a specific type for the generic `T`, like this: ```typescript const result: number[] = flatten<number>([1, [2, [3, 4]], 5]); ``` but the behavior continues. I suspect it has to do with the way TypeScript handles the recursive call and the type of the array being passed in. How can I fix the type inference in this recursive function to correctly handle nested arrays without losing the type safety? I'm using TypeScript 4.5.2 and want to ensure that any solution is also efficient, as I plan to use this in a larger application that frequently processes nested data structures. For context: I'm using Typescript on macOS. Any help would be greatly appreciated! This is my first time working with Typescript LTS. What would be the recommended way to handle this? The stack includes Typescript and several other technologies. Any examples would be super helpful. I recently upgraded to Typescript 3.11. I recently upgraded to Typescript stable. Could this be a known issue? I'm working in a Linux environment. How would you solve this? I'd be grateful for any help.