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

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

💻 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.

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.

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.

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

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never type does not work as expected in the function of a class #54265

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🙁 Actual behavior

🙂 Expected behavior

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never type does not work as expected in the function of a class #54265

Description

Bug Report

🔎 Search Terms

🕗 Version & Regression Information

⏯ Playground Link

💻 Code

🙁 Actual behavior

🙂 Expected behavior

Activity

MartinJohns commented on May 16, 2023

fatcerberus commented on May 16, 2023

microsoft-github-policy-service commented on May 19, 2023

microsoft-github-policy-service commented on May 19, 2023

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