Typescript Generics NOT with type

Question

Let's say i have an array of types:

const arr: Foo[]: [
  a: Foo<A>,
  b: Foo<B>,
  c: Foo<C>,
];

How to limit the array to be NOT a type

const arr: Foo<Not<B>>[]: [
  a: Foo<A>,
  b: Foo<B>, // error
  c: Foo<C>,
];

Can you show how Foo is defined?

Aleksey L.
– Aleksey L.

2020-06-10 12:41:39 +00:00
Commented Jun 10, 2020 at 12:41 — Aleksey L.
– Aleksey L., Commented Jun 10, 2020 at 12:41

bugs · Accepted Answer · 2020-06-10 10:38:47Z

1

One way of doing that is to use the Exclude utility type to specify a susbet of the type parameters that Foo can accept, something like this

type Foo<T> = {
    value: T
}

type Bar = string | boolean | number
type BarWithoutBoolean = Exclude<Bar, boolean>

const arr: Foo<BarWithoutBoolean>[] = [
    { value: 1     },
    { value: "abc" }, 
    { value: true  } // Err
]

answered Jun 10, 2020 at 10:38

bugs

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