How come we can spread a tuple but we cannot do the same thing with object types?

[empty cipher]

raswonders#0

Playground Link

Preview:```ts
type T1 = [number, string];
type T2 = [boolean, ...T1];
type T3 = [...T1, ...T2];

type O1 = { name: "Ras" };
type O2 = { age: 69 };
type O3 = { ...O1, ...O2 };```

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[marsh dirge]

I tried look up some official / unofficial docs but I didn't find anything which would give me insight on this one

[summer basin]

tuples are ordered, you kinda have to specify the order. for objects you can just do O1 & O2

T1 is basically { 0: number, 1: string }, but T2 should be { 0: boolean, 1: number, 2: string }
that's a more complicated operation, compared to just merging the properties like for objects

[marsh dirge]

Hey Thanks for reply, I don't quite follow how indexing could be a differentiator here.
I just tried with basic Array types, spread syntax seem to be working also there. https://www.typescriptlang.org/play/?#code/C4TwDgpgBAKgjFAvFA2gOwK4FsBGEBOANFAM7D4CWaA5gLoDcAUKJLAExKo4D23ANhACGaYgDpx8Bs3DQYAZk4pxo+GIlsp01gEEEyTLgIopLaNo77sefMaamo2hciXjda0edqMA9N6j+APQB+Ri1oAHk9KABvKDRBLAgALigAIgAlQRJUqABfOxkocIsYqEFqZKgANgBOPILWcKdS5Uj3YvqfP0CQoA

[empty cipher]

@marsh dirge Here's a shortened URL of your playground link! You can remove the full link from your message.

raswonders#0

Playground Link

Preview:```ts
type T1 = [number, string];
type T2 = [boolean, ...T1];
type T3 = [...T1, ...T2];

type A1 = number[];
type A2 = number[];
type A3 = [...A1, ...A2]
// ^?

type O1 = { name: "Ras" };
type O2 = { age: 69 };
type O3 = { ...O1, ...O2 };
// ^?```

You can choose specific lines to embed by selecting them before copying the link.

[marsh dirge]

for objects i get O1: any O2:any even though objects type declarations are right there...

[summer basin]

this syntax just isn't supported for object types.

because there's a more basic operation that does the same (well, slightly different) thing.

the indexing example is just explaining why array spread is a more complex operation than intersection

[marsh dirge]

Ah yeah thats actually great point

[summer basin]

if you need the runtime behavior of duplicate keys in O2 overriding those in O1, you can use Omit<O1, keyof O2> & O2