VS Code intellisense does not autosuggest when used with manual Typescript declaration file

Given this code for example:

// src/index.ts
export function hello(props: {
  type: 'boolean';
  params: {
    bool: boolean;
  }
}): void;
export function hello(props: {
  type: 'string';
  params: {
    str: string;
    num: number;
  }
}): void;
export function hello(props: {
  type?: any;
  params?: any;
}): void {
  console.log(props);
}


// index.ts
import { hello } from './src';

hello({
  type: 'string',  /* autosuggests 'string' and 'boolean' */
  params: {
    /* autosuggests `str` and `num` (not `bool`) as property options, which is correct and expected */
  }
})

The above code is working fine. However, when I transfer the same thing into .js file and .d.ts file, the same declaration doesn't work anymore:

// src/index.d.ts
export function hello(props: {
  type: 'boolean';
  params: {
    bool: boolean;
  }
}): void;
export function hello(props: {
  type: 'string';
  params: {
    str: string;
    num: number;
  }
}): void;
export function hello(props: {
  type?: any;
  params?: any;
}): void;


// src/index.js
export function hello(props){
  console.log(props);
}


// index.js
import { hello } from './src';

/* CTRL + clicking `hello` points me to the `src/index.d.ts` file, which is correct */
hello({
  type: 'string',  /* does not autosuggest anything */
  params: {
    /* does not autosuggest anything */
  }
})

Can anyone point me to the correct direction?