No error when accessing setter-only properties

🔎 Search Terms

"setter only", "setter-only"

🕗 Version & Regression Information

• This behavior is present in the current version of TypeScript, 5.4.4

⏯ Playground Link

https://www.typescriptlang.org/play?#code/MYGwhgzhAEBiD29oG8BQ0PQgUwC7QCMwAnACiIC8AuLXYgSwDsBzAShWgF9VvVh5GEfADNE0ALzRG2AO5xEpVgG4+AodABuYEAFdsNIQxYToo+ADoixJdAD0t6ABUAFvRiQI9ZowC22RvgQzvA6IAAmUvD4BNjQ2iDwMthhADSmiJYk0DL0ICBxIDJgAJ4wMdA6jGHYwkzJAIRAA

💻 Code

class Foo {
    set bar(baz: string) { }
}

const foo = new Foo();
const value: string = foo.bar; // This assignment should not be allowed, foo.bar will always be undefined!

🙁 Actual behavior

There is no error reported during type-checking.

🙂 Expected behavior

The type-checking should report an error for the assignment in the last line as foo.bar will always be undefined.

Additional information about the issue

#21759 is related, but that issue proposes a whole new language feature, this issue is solely about the lack of a type error.

Start with the linked TypeScript Playground and reproduce the setter-only property assignment to confirm the current type-checking behavior. Trace the type-checker path involved in reading foo.bar, then add coverage showing that assigning the read result to string reports an error without implementing the separate feature discussed in #21759.