noImplicitAny infers any for typed parameter of union's common function

[adamhamlin]

🔎 Search Terms

noImplicitAny any union

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about: noImplicitAny

⏯ Playground Link

https://www.typescriptlang.org/play?noImplicitAny=false&ts=4.9.5#code/JYOwLgpgTgZghgYwgAgLIE8Aq6AOKDeAUMicsACYD8AXMiAK4C2ARtANzGkhyMS0DOYKKADmHAL6FCMeiARhgAexDJG6AGKyEACgA2wQQHkoqODloZseANoBdZAB80ZgDyDhIEQBo0WXBAA+AEpaADdFCmQiUmR9IxMzADoYRSgAUUQAC21tRWYAKyDkAF4AqM4YknIIXQhIZDz8xIoOGPEgiUIgA

💻 Code

interface MyType {
    id?: number;
    name: string;
}

function myFunc(listOrMap: MyType[] | Map<string, MyType>): void {
    // When `noImplicitAny` is on, obj parameter is correctly inferred as `MyType`
    // When `noImplicitAny` is off, obj parameter is inferred as `any`
    listOrMap.forEach((obj) => {
        delete obj.id;
    });
}

🙁 Actual behavior

With noImplicitAny=false, the type of the forEach parameter is inferred as any.

🙂 Expected behavior

With noImplicitAny=false, the type of the forEach parameter is inferred as MyType

Additional information about the issue

Fyi, the type is correctly inferred when noImplicitAny=true, or if not using the union type for myFunc's parameter

[MartinJohns]

This is working as intended: #52748 (comment)

[adamhamlin]

Ok, thanks for the info @MartinJohns