Another patch for Nominal Type

[andresmoschini]

In this article, as a introduction to another thing, the author shows another kind of patch to use nominal types:

interface PersonIdBrand { _type: "Person"; }
type PersonId = PersonIdBrand & number;

interface BlogPostIdBrand { _type: "BlogPost"; }
type BlogPostId = number & BlogPostIdBrand;

It worked better for me with type inference than your approach with enums.

Do you think that is a good idea to add this alternative? or is there a well known issue with this approach?

[andresmoschini]

The type inference works better for me in this scenario:

type A = string & { _type: 'A' };
type B = string & { _type: 'B' };
type C = string & { _type: 'C' };
type D = A | B | C;

const f = (a: A, b: B, c: C) => a || b || c; 
// Infers: const f: (a: A, b: B, c: C) => D ✅

enum ABrand {  _ = '' }
type A = string & ABrand;
enum BBrand {  _ = '' }
type B = string & BBrand;
enum CBrand {  _ = '' }
type C = string & CBrand;
type D = A | B | C;

const f = (a: A, b: B, c: C) => a || b || c; 
// Infers: const f: (a: A, b: B, c: C) => C 💔

[andresmoschini]

An alternative, more similar to your Interface related one is:

type A = string & { _aBrand: any; }
type B = string & { _bBrand: any; }
type C = string & { _cBrand: any; }
type D = A | B | C;

const f = (a: A, b: B, c: C) => a || b || c;
// Infers: const f: (a: A, b: B, c: C) => D ✅

[basarat]

:+1: Needs to be added as Using intersection types at some point :rose: