For Typescript intersection type (type C = A & B), how to see resulting type signature instead of components in IDE hints?

Question

In Typescript, when inspecting types defined by intersection, I see a hint identical to original definition:

but I would like to see the resulting shape, something like this:

what is a quick / efficient way to do this?

Please edit the question to include the code in the images as text also, as described in [ask]. — jcalz, May 01 '20 at 14:39
Possible duplicate of [How can I see the full expanded contract of a Typescript type?](https://stackoverflow.com/questions/57683303/how-can-i-see-the-full-expanded-contract-of-a-typescript-type) — jcalz, May 01 '20 at 14:46

score 1 · Accepted Answer · answered May 01 '20 at 14:51

I don't think there's any way to ask your IDE to do this automatically, but you can make a type function that calculates the type you're looking for. From the answer to the question is duplicates, I would write Expand:

type Expand<T> = T extends infer U ? { [K in keyof U]: U[K] } : never;

which takes a type (or union of types) and walks through all of its properties, even if they come from multiple intersections, and packages it (or each union member) into a single object type. Then you could either write Expand<C> or you could define C to be Expand<A & B>:

type ExpandedC = Expand<A & B>;
/*
type ExpandedC = {
    a: number;
    b: string;
    c: boolean;
    d: Date;
}
*/

which is what you wanted. Okay, hope that helps; good luck!

Playground link to code

For Typescript intersection type (type C = A & B), how to see resulting type signature instead of components in IDE hints?

1 Answers1