Regression in `asserts` behavior modifying type of `this`

Bug Report

🔎 Search Terms

asserts regression

🕗 Version & Regression Information

• This changed between versions 4.9.5 and 5.0.4

⏯ Playground Link

Playground link with relevant code

💻 Code

export class Set<S extends number[] = []> {
  insert<_>(x: any): asserts this is Set<[...S, 0]> {}
}

const y: Set = new Set();
y.insert(6);
y
//^?
y.insert(6);
y
//^?

🙁 Actual behavior

In 5.0.4

//^? const y: Set<[]>
//^? const y: Set<[]>

🙂 Expected behavior

In 4.9.5

//^? const y: Set<[0]>
//^? const y: Set<[0,0]>

Start with the linked TypeScript Playground and compare the reported behavior in versions 4.9.5 and 5.0.4. Investigate how the asserts method changes the type of this across successive insert calls. Done means the example narrows y to Set<[0]> after the first call and Set<[0,0]> after the second.