If I understand correctly, you want OneKey<“a” | “b”> to be something like {a: any, b?: never} | {a?: never, b: any}. Meaning that it either has an a key or a b key but not both. So you want the type to be some sort of union to represent the either-or part of it. … Read more
Use float only, as int is implied in that type: def my_func(number: float): PEP 484 Type Hints specifically states that: Rather than requiring that users write import numbers and then use numbers.Float etc., this PEP proposes a straightforward shortcut that is almost as effective: when an argument is annotated as having type float, an argument … Read more
Edit for 4.2 map has become callable now, but you still need an explicit type annotation on its argument to get it to work as expected (the type parameter is no contextually typed) let test: Test1[] | Test2[] = []; test.map((obj: Test1 | Test2) => {}); Playground Link This situation is likely to improve in … Read more
To understand the keyof typeof usage in TypeScript, first you need to understand what are literal types and union of literal types. So, I’ll explain these concepts first and then explain keyof and typeof individually in detail. After that, I’ll come back to enum to answer what is asked in the question. It’s a long … Read more
T‘s type must be consistent across multiple uses within a given scope, while U‘s does not. With a Union type used as function parameters, the arguments as well as the return type can all be different: U = Union[int, str] def union_f(arg1: U, arg2: U) -> U: return arg1 x = union_f(1, “b”) # No … Read more
Here’s the closest I can imagine getting, although I still don’t understand why we don’t just use plain objects to begin with: type ObjectToEntries<O extends object> = { [K in keyof O]: [K, O[K]] }[keyof O] interface ObjectMap<O extends object> { forEach(callbackfn: <K extends keyof O>( value: O[K], key: K, map: ObjectMap<O> ) => void, … Read more
DISCLAIMER: DON’T DO THIS!! If someone tells you to use the code they found in this answer to do anything except demonstrate why this is a bad idea, RUN AWAY!! It’s easy to convert from a tuple type to a union type; for example, see this question. But the opposite, converting from a union to … Read more