Type is not referred correctly in the while loop

🔎 Search Terms

incorrect type while loop

🕗 Version & Regression Information

Worked correctly in version 4.2.3.
It doesn't work since 4.3.5.

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.5.4#code/MYGwhgzhAEDCAWBLEATaBTAHgF3QOxRgAkAVAWQBkBREdAW322gG8AoASAHN0mAHMAE6MAFAEoWHdsAD2eCE2bR+QvNhr1G0AL7QAvNGxIIAblaTEAM2jCAhMOWN1DVdERzsYPMHTSrABUFGUXE2djChbABXATxoPEiQEFMwrTNwnmjYh1UnRmTU1NZQSBgAlSYsXAJicmpaZwUObj5A1TEJMJl3FiVWtXrNHX1DRBM09ktrO2z+jRc3eU9vX2gAcQFPFDKgkMl2CMy4hKTJQvSomN7y3NV81kLiqDWNgm2XSvxCaFJKG8auHhXES7TqyeQ9GZ-bR6AxGUzmKy2ex9KELDxeHxWdboMDYdabN7YYIdc6HeKJZLsM77DKXSEDW4cApmR4wbG4-GvPoYHCfGq-Bn-ZpAtogmkXWLkk5U+4syLyaR0P4QAB0KHQFjc6GEACJgABaYBIVA6gA0cGNKFEpmA8uwiuVao1Wt1BpmZughOtRTtDsFqvVmrw2r1+s4LxQ+vd5s5Wz63ttCqV-qdQZDBvDOOwYYjUb6HvZeIjXvh2AAnrx0J6Uf6YYXY4ToAAfZ4E7ktwnwrrgo3IND6YMAdwtfbE8NoTFtAnKhIAXNXrrWW1KYb3UCqZvDB8aq8IpzP4x1u9JaCqQNJOHvogfytboAB6e-QCDwaQJNAAIyr9eL7dbXPKZsF0YNJ90YRt9DA1RCQ3PpTFSIA

💻 Code

class Child extends HTMLElement {
	get parent() {
		const { parentElement } = this;

		if (!(parentElement instanceof Parent)) {
			return null;
		}

		return parentElement;
	}
}

class Parent extends HTMLElement {
	get parent() {
		const { parentElement } = this;

		if (!(parentElement instanceof GrandParent)) {
			return null;
		}

		return parentElement;
	}
}

class GrandParent extends HTMLElement {
	get parent() {
		const { parentElement } = this;

		if (!(parentElement instanceof GreatGrandParent)) {
			return null;
		}

		return parentElement;
	}
}

class GreatGrandParent extends HTMLElement {
	get parent() {
		return null;
	}
}

// irrelevant code
customElements.define("c-child", Child);
customElements.define("c-parent", Parent);
customElements.define("c-grand-parent", GrandParent);
customElements.define("c-great-grand-parent", GreatGrandParent);

type ParentElements = GreatGrandParent | GrandParent | Parent;

const child = new Child();

let currentParent: ParentElements | null = child.parent;

while (currentParent) {
	console.log(currentParent); // should be GreatGrandParent | GrandParent | Parent

	currentParent = currentParent.parent;
}

🙁 Actual behavior

The curerntParent's type is not referred correctly. It became Parent | GrandParent.

🙂 Expected behavior

The currentParent's type should be Parent | GrandParent | GreatGrandParent.

Additional information about the issue

No response

Inizia con la riproduzione collegata in TypeScript Playground e confronta il suo comportamento con le versioni 4.2.3, 4.3.5 e quella attuale. Traccia come il restringimento del tipo venga mantenuto attraverso il ciclo while e la sua riassegnazione. Il lavoro è completato quando currentParent rimane tipizzato come Parent | GrandParent | GreatGrandParent senza regredire rispetto al comportamento precedente.