Missing property when inferring from object literals in array literals

[dragomirtitian]

Bug Report

🔎 Search Terms

object literal method union reduce

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ

⏯ Playground Link

Playground link with relevant code

💻 Code

let a =  [
    { foo: 0, m() { } },
    { bar: 1 }
]
declare let n: number
a[n].m

🙁 Actual behavior

TypeScript behaves as if m in present on a[n] when trying to access in a[n].m (as it does for foo and bar as well), but generated declarations don't reflect this:

declare let a: ({
    foo: number;
    m(): void;
    bar?: undefined;
} | {
    bar: number;
    foo?: undefined;
})[];

With the above declaration for a (from generated declarations), we couldn't access a[n].m (PL).

Tooltips also display the same type as declarations omitting m in the second constituent of the union.

🙂 Expected behavior

Methods in object literals should behave the same as properties when the type of the array is inferred (if a method is missing in one of the objects, an optional member with type undefined should be inferred:

declare let a: ({
    foo: number;
    m(): void;
    bar?: undefined;
} | {
    bar: number;
    foo?: undefined;
    m?: undefined;
})[];