🔎 Search Terms

• type narrowing
• return type never
• error
• throw
• method
• chaining
• error 7027

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for any entries relating to return type never

⏯ Playground Link

https://tsplay.dev/wQqAZw

💻 Code

const throwError = (message: string): never => {
  throw new Error(message);
}

type Thrower = typeof throwError;

const errorContext = {
  throwError
};

type ErrorContext = typeof errorContext;

const test1 = (thrower: Thrower) => {
  throw new Error('foo');

  // following code results in 7027 "unreachable code detected" as expected

  console.log('bar');
};

const test2 = (thrower: Thrower) => {
  thrower('foo');

  // following code results in 7027 "unreachable code detected" as expected

  console.log('bar');
};

const test3 = (errorContext: ErrorContext) => {
  errorContext.throwError('foo');

  // following code does NOT result in 7027, although the code is unreachable at runtime

  console.log('bar');
};

🙁 Actual behavior

If a function that returns never is a method, it does not result in error 7027 "unreachable code detected" or any
expected type-narrowing for subsequent code when called.

🙂 Expected behavior

Any code after a call to a function that always returns never should result in error 7027 "unreachable code detected" and any expected type-narrowing regardless of whether that function is method or a standalone function.

Additional information about the issue

No response