Better error message when a module declaration is not found, but a module augmentation is?

🔎 Search Terms

declaration, augmentation

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about module augmentation and declaration files

⏯ Playground Link

Can't be shown on Playground, since it requires two files

💻 Code

// declaration.d.ts

import { ComponentType } from "react";

declare module "a/b" {
    const B: ComponentType<any>;
    // const B: import("react").ComponentType<any>;
    export default B;
}

// file.ts
import B from "a/b";

🙁 Actual behavior

The error message is "Cannot find module 'a/b' or its corresponding type declarations (2307)". I know this works as indended from https://github.com/microsoft/TypeScript/issues/49043#issuecomment-1124047244, so my proposal is only about changing the error message.

🙂 Expected behavior

In the case where TypeScript can't find a declaration of a module but can find its augmentation, it seems very likely the user intended to make it a declaration, but didn't know top-level import/export change the meaning (like I didn't yesterday). It would be nice to have the message tell the user about the problem and guide to fixing it.

Reproduce the behavior with the two files shown, declaration.d.ts and file.ts, and compare the diagnostic when the module declaration is missing but its augmentation is found. Trace the module-resolution diagnostic path and update the message to explain the top-level import/export distinction; verify the revised guidance against this example and related diagnostic tests.