Using @ts-expect-error on class method signature would disable checking all other methods in interface

[fenying]

🔎 Search Terms

ts-expect-error missing method

🕗 Version & Regression Information

• This is the behavior in every version I tried between v4.0 and v5.5, didn't try older versions

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.5.3#code/KYDwDg9gTgLgBASwHY2FAZgQwMbDgSQBVgBneAbwChK5a5MAKASgC44A3CBAEwG5q6cAEbM2nHvwC+1UJFhxsAG0wkScYmUQBbMIuBbgKNUVIUBdAPQW4AARgkAtLODYYTqFGg06YAK5DFBGx6BgBrNjIoZABzVg4ubjhyaWkgA

💻 Code

export interface ITest {

    a(): void;

    b(): void;
}

export class Test implements ITest {

    // @ts-expect-error
    public a(k: string): void {}

    // method b is missing, but no errors reported
}

🙁 Actual behavior

No error reported even missing a method in the class

🙂 Expected behavior

Should report errors if any method is not implemented in class

Additional information about the issue

No response

[MartinJohns]

ts-expect-error is not the culprit here, you also don't get the error you expect when you remove it. The compiler doesn't check if your class implements the interface when there's already an error inside your class. Using ts-expect-error does not remove the error and let the compiler happily continue its job, it just hides the error.

Related comment: #47551 (comment)

once your program has a type error in it, it's up to our heuristics to decide exactly what the most useful reporting of that type error is.

[fenying]

OH. I see, the compiler stops checking next error if it meet an error, until this one got resolved :(