never type does not work as expected in the function of a class

[SkyGrasperKnight]

Bug Report

🔎 Search Terms

• never
• class
• function

🕗 Version & Regression Information

• Version: 5.0.4
• This is the behavior in every version I tried, and I reviewed the FAQ for entries about never type and class

⏯ Playground Link

Playground link with relevant code

💻 Code

function throwErrorFunction() : never {
  throw new Error("Error in function")
}

class ErrorService {
  throwErrorClass(): never {
    throw new Error("Error in class")
  }
}


function neverNotWorkingAsExpected() {
  const errorService = new ErrorService();
  errorService.throwErrorClass();
  
  // The following line should be detected as unreachable
  throwErrorFunction();
}

function neverWorkingAsExpected() {
  throwErrorFunction();

  // The following code is detected as unreachable
  const errorService = new ErrorService();
  errorService.throwErrorClass();
}

🙁 Actual behavior

Code following a function of a class of type 'never' is not considered inaccessible.
It does not have the same behavior as a function that is not in a class.

🙂 Expected behavior

The never type is correctly handled when used in a function of a class.
So after using the function, the following code is considered unreachable.

[MartinJohns]

It's a known design limitation, see #32695.

A function call is analyzed as an assertion call or never-returning call when

• the call occurs as a top-level expression statement, and
• the call specifies a single identifier or a dotted sequence of identifiers for the function name, and
• each identifier in the function name references an entity with an explicit type, and
• the function name resolves to a function type with an asserts return type or an explicit never return type annotation.

Duplicate of #36753.

[fatcerberus]

In particular, the important part here is...

each identifier in the function name references an entity with an explicit type

"Function name" meaning "call target", in this case errorService.throwErrorClass. errorService doesn't have a type annotation.

[microsoft-github-policy-service]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.

[microsoft-github-policy-service]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.