No error when namespace export is used before assigned

TypeScript Version: 2.6.2

Search Terms: namespace decorator same class

Code

@C1.Decorator
export class C1{ }
export namespace C1 { 
  export function Decorator<T>(target: T) { }
}
@C1.Decorator
@C2.Decorator
export class C2 { }

export namespace C2 { 
  export function Decorator<T>(target: T) { }
}

Expected behavior: if this is not a feature, decorator should be defined at runtime, or it should provide some warning or error during compilation?

Actual behavior: decorator from namespace C1 used on class C1 is undefined, decorator from C1 is defined when used on C2, decorator from C2 is undefined

Playground Link: https://www.typescriptlang.org/play/index.html#src=%40C1.Decorator export class C1{ } export namespace C1 { export function Decorator<T>(target%3A T) { } } %40C1.Decorator %40C2.Decorator export class C2 { } export namespace C2 { export function Decorator<T>(target%3A T) { } }

Related Issues: I did not find any

[andy-ms]

It looks like the general problem is that we don’t give you a used-before-assigned error for a variable in a namespace.

console.log(N.x);
namespace N {
    export const x = 0;
}

It seems like we could do this, so marking as a bug for now.

[sandersn]

Now that functions support expando properties in TS (and have for some time in JS), the same bug repros there:

f.p // should have an error here
function f() {}
f.p = { x: "" };
f.p // ok