Namespaces: use before declaration is not reported

[yarden-app]

🔎 Search Terms

Namespace, use before declaration, initialized variable

🕗 Version & Regression Information

• This is the behavior in every version I tried.

⏯ Playground Link

https://www.typescriptlang.org/play/?target=99&jsx=0&module=1&ts=5.9.0-dev.20250618#code/KYDwDg9gTgLgBAOwIYFtgGcxIMbDgQQG8AoOOUSWRVDLXAgRjhLLIunmwgXXgDMEcALxwAFAEphAPjgAiXlACWCAOazScAL7EN7KsjSYcefACYWrPZ2684SKFCQBPYXADa+AMwA6AG5IAGwBXYABdDW1dcA5qQzoTTws2aKouHnh-YLwRfAZvAQkI4k0gA

💻 Code

export namespace A{
  export namespace A1 {
    export const fn = () => "string"
  }

  export namespace A2{
    // should report use before initialization here 
    export const array = [A3.value]
  }

  export namespace A3{
    export const value = A1.fn()
  }
}

🙁 Actual behavior

Hi, using typescript V5+, the code provided did not reports any errors, and doesn't work in runtime due to use before initialization.

🙂 Expected behavior

It is expected that TS2448 and TS2454 will be reported.(use before declaration)
These are reported if the namespace keyword is omitted in the code example and it should be the same when namespaces are used.
It seems files with namespaces are always transpiled with the same format using any TS configuration. (everything becomes iife)

Additional information about the issue

Optimistically additional support for namespace will be added, such as not transforming the entire file to iife when namespaces are used- which happen on any configuration.

And maybe even an option to make a code like I've sent work, by isolating these namespaces properly, and resort their order by their variable dependencies between themselves, and report when cycling variable dependency between namespaces exists.

[azerum]

Simpler example where code compiles, but fails at runtime:

function f(n: number) {
    return n.toFixed(2)
}

const theAnswer = f(Foo.answer)

namespace Foo {
    export const answer = 42.001
}

Which seems surprising as using class instead of namespace does report the error. I wonder what makes them different with respect to type checking:

function f(n: number) {
    return n.toFixed(2)
}

// Class 'Foo' used before its declaration. ts(2449)
const theAnswer = f(Foo.answer)

class Foo {
    static answer = 42.001
}

[copilot-swe-agent]

@RyanCavanaugh Unfortunately I hit an unexpected error while trying to work on issue #61891. I've automatically reported this to GitHub.

You can ask me to try again later by unassigning and then reassigning the issue to me again.

If you want to contact GitHub about this error, please mention the following identifier so they can better serve you: 4bc79f4d-890e-4ae8-ad10-ab6aa779b77c

Sorry for the inconvenience!

[yarden-app]

I purposely use that code example to complement my "optimistic" request. This will really help with the semantic of the module/file. Like how you would declare greater functions before lesser one in the same file.

I don't want to use ambient namespace and want to avoid declare keyword. Both which do not support nesting properly, which is kind of the main thing about namespace anyway.

Thanks

[copilot-swe-agent]

@RyanCavanaugh Unfortunately I hit an unexpected error while trying to work on issue #61891. I've automatically reported this to GitHub.

You can ask me to try again later by unassigning and then reassigning the issue to me again.

If you want to contact GitHub about this error, please mention the following identifier so they can better serve you: 19689387-b3ca-4037-9cb2-b3fb4268874a

Sorry for the inconvenience!