Type issue for a resolved promise (Svelte/TypeScript)

I have the following simplified Svelte code in Typescript:

<script lang="ts">
	import axios from 'axios';
	import { env } from "$env/dynamic/public";
	import type { Submission } from '../models/submission';

	let submissionUuid: string | undefined;
	let submissionStatusResponse = Promise.resolve(String);
    // let submissionStatusResponse = Promise<string>; // not sure about the difference

	const postSubmission = async (file: File): Promise<Partial<Submission>> => {
		const formData = { file: file };
		const { data, status } = await axios.post(env.PUBLIC_API_BASE_URL + '/submissions/', formData, {
			headers: { 'Content-Type': 'multipart/form-data' }
		});
		if (status === 200) {
			// console.log(JSON.stringify(data));
			return data;
		}
	};

	const getSubmissionStatus = async (uuid: string) => {
		const { data, status } = await axios.get(env.PUBLIC_API_BASE_URL + '/submissions/' + uuid);
		if (status === 200) {
			// console.log(JSON.stringify(data));
			return data.status;
		}
	};

	function handleSubmit() {
		let submissionResponse: Promise<Partial<Submission>> = postSubmission(
			document.getElementById('file').files[0]
		);
		submissionResponse.then((submission) => {
			submissionUuid = submission.uuid;
			submissionStatusResponse = getSubmissionStatus(submissionUuid);
		});
	}
</script>

<form on:submit|preventDefault={handleSubmit}>
	<label for="file">Select a file</label>
	<input type="file" id="file" name="file" required />
	<button type="submit">Submit</button>

	{#await submissionStatusResponse then submissionStatus}
		{submissionStatus}
	{:catch error}
		Error getting submission status from API: {error.message}
	{/await}
</form>

But in the web page the it renders the string function String() { [native code] } instead of the resolved value of submissionStatus.

There must be indeed a type issue since the following Typescript alert is raised on the component Status, when passing the supposedly resolved submissionStatus string: Type 'StringConstructor' is not assignable to type 'string'.

What am I doing wrong here?

The problem is that you are assigning submissionStatusResponse rather than annotating it:

let submissionStatusResponse = Promise.resolve(String);

So then Promise can resolve String right away. The result is function String() { [native code] } (try doing console.log(String) for comparison).

I think you want:

let submissionStatusResponse: Promise<string>; // A promise that will return a string

Then, once the promise is resolved, a string will be returned.