Function returning spread operator infers wrong type and get properties can be accessed

[michaelcheers]

Bug Report

⏯ Playground Link

Playground link with relevant code

💻 Code

class Test{get Length(){return 1;}}

function spread<T> (t: T) { return {... t} }
let test1 = {...new Test()};
console.log(test1.Length); // Expected: throws error. Actual: throws error.
let test2 = (o => ({...o}))(new Test());
console.log(test2.Length); // Expected: throws error. Actual: throws error.
let test3 = spread(new Test());
console.log(test3.Length); // Expected: throws error. Actual: doesn't throw error.

🙁 Actual behavior

Doesn't throw compile-time error.
Error is at runtime, the spread operator of Test does not copy over properties.

🙂 Expected behavior

Typescript's type system should figure out that the type is not T but instead is just enumerable properties of T.

[RyanCavanaugh]

See #9726