Tooltip on private fields not showing the correct type after narrowing

[SuspiciousLookingOwl]

Bug Report

🔎 Search Terms

private field, class, narrow, narrowing

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

Playground link with relevant code

💻 Code

class TestClass {
    #privateProperty: string[] | null;
    publicProperty: string[] | null;

    constructor() {
        this.#privateProperty = null;
        this.publicProperty = null;
    }

    testMethod() {
        if (this.#privateProperty === null)
            return;
        if (this.publicProperty === null)
            return;

        this.#privateProperty; // string[] | null
        this.publicProperty; // string[]

        const a = this.#privateProperty;
        a; // string[]
    }
}

🙁 Actual behavior

this.#privateProperty is string[] | null even after narrowing down the type from if. Also assigning this.#privateProperty to other variable fixes the type.

🙂 Expected behavior

this.#privateProperty should be string[] after narrowing down

[MartinJohns]

The type of this.#privateProperty is narrowed to string[]. It's just the tooltip that reports the wrong type.