Incomplete infer for generic types

TypeScript Version: 4.0.5

Search Terms:
typescript, infer, incomplete, unknown, generic

Expected behavior:
The compiler should be able to extract information of the generic Item type from the function definition and infer string.

Actual behavior:
The compiler is able to infer the Names type as { id: string } but the Item type is unknown.

Related Issues:

Code

interface LoaderConfig<Key, Item> {
  loadItems: (keys: readonly Key[]) => Promise<readonly Item[]>;
  getKey: (item: Item) => Key;
  makeCacheKey: (key: Key) => string;
}

type LoaderConfigByName<Names, Item> = {
  [name in keyof Names]: LoaderConfig<Names[name], Item>;
};

function makeLoader<Names, Item>(
  configs: LoaderConfigByName<Names, Item>
): void {
  console.log(configs);
}

makeLoader({
  id: {
    loadItems: async (keys: readonly string[]): Promise<readonly string[]> => {
      return await Promise.resolve(keys);
    },
    getKey: (item: string): string => item,
    makeCacheKey: (key: string): string => {
      return key;
    }
  }
});

"use strict";
function makeLoader(configs) {
    console.log(configs);
}
makeLoader({
    id: {
        loadItems: async (keys) => {
            return await Promise.resolve(keys);
        },
        getKey: (item) => item,
        makeCacheKey: (key) => {
            return key;
        }
    }
});

{
  "compilerOptions": {
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictPropertyInitialization": true,
    "strictBindCallApply": true,
    "noImplicitThis": true,
    "noImplicitReturns": true,
    "alwaysStrict": true,
    "esModuleInterop": true,
    "declaration": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "moduleResolution": 2,
    "target": "ES2017",
    "jsx": "React",
    "module": "ESNext"
  }
}

Playground Link: Provided

Inizia con il link Playground fornito e con l’esempio generico makeLoader usando TypeScript 4.0.5. Riproduci il risultato dell’inferenza e traccia la gestione da parte del compilatore del tipo generico Item. Il lavoro è completato quando l’esempio inferisce Item come string mantenendo il tipo Names inferito.