See #9726 - TS would need a way to know that the array methods don't end up on foo.

@RyanCavanaugh is this really a design limitation due to lack of enumerable properties? I believe in a very similar case for objects (not arrays) the type is correctly inferred:

class Customer {
  constructor(public name: string) {}
  greet() {
    return 'Hello ' + this.name;
  }
}
var customer = new Customer('David');
var clone = {...customer};
// console.log(clone.greet()); //Does not compile

Playground

Could we have similar feature for arrays?

yeah i found that too doing a reduce and accidentally returning {...acc} instead of [...acc]. i was puzzled by why TS would be happy about it 😄

@sebapawlak TS knows which members of a class are enumerable and which aren't, but we don't have any declaration form for annotated the value-declared type of Array to provide that information. That's literally what I'm talking about re #9726