TypeScript type that enforces that one and only one property is accepted from another interface

Question

I would like a type to enforce the following

given:

interface Foo {
    key1: bool;
    key2: string;
    ...: 
    keyn: <whatever>;
}

I'd like something like:

OnlyOnePropery<Foo>

where only following would be accepted for the type:

• { key1: bool;} xor {key2: string;} xor ... xor {keyn: <whatever>;}

So basically one and only one key value pair.