Return type of exported function has or is using name X from external module Y but cannot be named.

[icopp]

🔎 Search Terms

"cannot be named", "has or is using name", "return type of exported function"

🕗 Version & Regression Information

• This changed between versions 5.7.0 and 5.8.2

⏯ Playground Link

n/a (this requires 2+ files)

💻 Code

// file 1
declare const emptyObjectSymbol: unique symbol;

export interface EmptyObject {
  [emptyObjectSymbol]?: never;
}

// file 2
import type { EmptyObject } from 'file1';

function a() {
  return {} as EmptyObject;
}

// file 3
import { a } from 'file2';

function b() { // error here
  return a()
}

🙁 Actual behavior

error TS4058: Return type of exported function has or is using name 'emptyObjectSymbol' from external module "file1" but cannot be named.

Additional information about the issue

🙂 Expected behavior

The code compiles as expected.

No response

[fregante]

Without a full repro, this is just a duplicate of #58914. Your issue in type-fest mentions references, which your example code above does not contain (and likely does not trigger the bug)

If you can create a small repro, the maintainers have been looking for one for a while.

[RyanCavanaugh]

Without other configuration info, "file1" is not a valid way to refer to file1.ts, maybe you meant "./file1"?

function b() is not exported, so there's no way you got the "return type of exported function..." error

Fixing both those problems, I can emit file3.d.ts without error, it shows

export declare function b(): import("./file1").EmptyObject;

Please provide a new issue with a fully-working repo; we cannot act on reports that require this much inference as to what you're actually doing