Plugin seems to prefer "*.mts" file over "*.d.mts" file.

[eXory2024]

Checklist

• I can reproduce this issue when running this plugin on its own.
  Other plugins, such as node-resolve are known to cause issues.
• I am running this plugin on .d.ts files generated by TypeScript.
  The plugin can consume .ts and even .js files (with allowJs: true), but this is known to cause issues.
• This issue is not related to rolling up @types.
  The plugin ignores these by default, unless respectExternal is set. @types can contain hand-crafted code which is known to cause issues.

Code Snipped

Entry point: (test.d.mts):

// Your code that is causing problems.
export type {myFunction} from "./myFunction.d.mts"

Where myFunction.d.mts is:

export function myFunction(a : string) : string;

And myFunction.mts is:

export function myFunction(a : string) : string {
	return `${a}`
}

Error Message

There is no error message but the output is:

declare function myFunction(a : string) : string {
	return `${a}`
}

export { myFunction };

Which obviously is wrong for a .d.mts file.

Removing the myFunction.mts file makes the plugin output the correct code:

declare function myFunction(a : string) : string;

export { myFunction };

Rollup config:

import {dts} from "rollup-plugin-dts"

export default {
	input: "./src/test.d.mts",

	output: {},

	plugins: [
		dts()
	]
}

I made a repo for easy cloning & reproduce the problem described here.

[eXory2024]

File extension doesn't matter, if you change .d.mts to .d.ts and .mts to .ts the behaviour is the same.

[eXory2024]

It looks like the plugin does to the correct thing when the entry point is renamed from .d.mts to simply .mts.