Wrong types inferred when using partial interfaces

[ivancuric]

import { merge } from 'merge-anything';

interface Pokemon {
  name: string;
  type: string;
}

const original: Pokemon = { name: 'Squirtle', type: 'water' };

const updatePokemon = (partial: Partial<Pokemon>) => {
  const evolution = merge(original, partial);
  return evolution; // resolved as `Partial<Pokemon>` when it should be `Pokemon`
};

https://stackblitz.com/edit/vitejs-vite-myssqmhr?file=src%2Fmain.ts,package.json&terminal=dev

[mesqueeb]

@ivancuric PRs welcome

[salisbury-espinosa]

@ivancuric PRs welcome

@mesqueeb @ivancuric You can see how type inference was implemented here:
https://github.com/sindresorhus/type-fest/blob/main/source/merge-deep.d.ts

=>

import type {MergeDeep} from 'type-fest';
import { merge } from 'merge-anything';

interface Pokemon {
  name: string;
  type: string;
}

const original: Pokemon = { name: 'Squirtle', type: 'water' };

const updatePokemon = (partial: Partial<Pokemon>) => {
  const evolution = merge(original, partial) as MergeDeep<
      typeof partial,
      typeof original
    >;
  return evolution; // resolved as `Partial<Pokemon>` when it should be `Pokemon`
};

PS
There is a small issue though
sindresorhus/type-fest#1314

By the way, behavior of Merge (from 'merge-anything) is incorrect

import type { Merge } from 'merge-anything';
interface Pokemon {
      name: string;
      type: string;
    }

valid:

const testThroughAssert: Pokemon = {} as Merge<Partial<Pokemon>, [Pokemon]>;

not valid:

const testThroughAssert: Pokemon = {} as Merge<Pokemon, [Partial<Pokemon>]>;

=>error TS2322: Type 'Partial<Pokemon>' is not assignable to type 'Pokemon'.

the correct operation of this utility depends on the order of types!
but on complex nested structures this type (Merge) always breaks, but MergeDeep from type-fest - not!

[mesqueeb]

@salisbury-espinosa can you do an experimental PR we can work off of? feel free to try a version that uses MergeDeep type from type-fest.