Module is present in declarations even though it is unused.

🔎 Search Terms

module unused declarations

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.2.2#code/KYDwDg9gTgLgBAbwL4CgAmwDGAbAhlYOAWwjQFdtCS0BGRFORuUSWOGATzEJmAGcYdALxwBUAJYA7AOYBuFKgw58VUhVVoATPSZxxRVvF4DhxUjQB0xwfN0to8BO36C4SeUiA

💻 Code

export {}
declare module mod1 {
    export type test1 = string;
}
declare module mod2 {
    import test1 = mod1.test1;
    export { test1 };
}

🙁 Actual behavior

mod1 is kept in the declaration.

🙂 Expected behavior

mod1 is not kept in the declaration file since it is only used in mod2 which is omitted from the declaration file.

Additional information about the issue

Found while working on isolated declarations in test reExportAliasMakesInstantiated.ts added by #54816 (cc @andrewbranch )

Reproduce the behavior with the linked TypeScript Playground example, then read the isolated-declarations test reExportAliasMakesInstantiated.ts mentioned in the issue and compare its emitted declaration output. Done means the unused mod1 declaration is omitted when mod2 itself is omitted from the declaration file, with the relevant test covering the behavior.