TypeScript: never-returning branches should not be considered when determining whether a property is initialized in a constructor

🔎 Search Terms

constructor, initialization, initialized, 2564, never, throw, error

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

https://tsplay.dev/w6Q9yW

💻 Code

const throwParseError = (def: unknown): never => {
    throw new Error(`${def} is not a valid definition`)
}

class Foo {
    // Property 'bar' has no initializer and is not definitely assigned in the constructor.(2564)
    bar: string

    constructor(def: string | null) {
        if (def === null) {
            // this return pattern is useful for narrowing
            // if you remove `return` here, the initialization error goes away
            // but the assignment to bar is then an error
            return throwParseError(null)
        }
        this.bar = def
    }
}

🙁 Actual behavior

TypeScript reports that Property 'bar' has no initializer and is not definitely assigned in the constructor.(2564)

🙂 Expected behavior

TypeScript should identify that in every viable branch of the constructor, bar is assigned.

Additional information about the issue

No response