[int_19h]

C# supports top-level functions as well, that's not the issue. But, just to give a simple example, in TS you can do things like:

   var foo: { bar: { baz: string } }

which have no equivalent in C#, because it doesn't have anonymous struct types, and its typing system is almost entirely nominal. Go, on the other hand, can translate this directly pretty much mechanically:

   var foo struct { bar struct { baz string } } 

And keep in mind that they aren't completely ditching the existing implementation, either, so for a while they're going to have to e.g. fix bugs in both side by side. It helps when the code can also be mapped almost 1:1.

[CharlieDigital]

The interesting thing is that you can do this in C# with tuples because tuples can nest tuples.

    type Platform = "Mastodon" | "Bluesky" | "Threads";

    type Profile = {
      name: string,
      socials: {
        handle: string,
        platform: Platform
      }[]
    }

    function getProfiles() : Profile[] {
      return [{
        name: "Charles",
        socials: [
          { handle: "@chrlschn", platform: "Mastodon" },
          { handle: "@chrlschn", platform: "Bluesky" }
        ]
      },
      {
        name: "Sandra",
        socials: [
          { handle: "@sndrchn", platform: "Threads" }
        ]
      }]
    }

Versus:

    using Profile = (
      string Name,
      (
        string Handle,
        Platform Platform
      )[] Socials //  Array of tuples in another tuple
    );

    enum Platform { Mastodon, Bluesky, Threads }

    Profile[] GetProfiles() => new[] {
      ("Charles", new[] {
        ("@chrlschn", Platform.Mastodon),
        ("@chrlschn", Platform.Bluesky),
      }),
      ("Sandra", new[] {
        ("@sndrchn", Platform.Threads)
      }),
    };

With some caveats

[afiori]

I would love if in mapping the typescript types to go they ended up building a "compiler plugin" to enhance go's type system.

[bheadmaster]

TypeGo by Microsoft (TM).

Considering how fast the TypeScript compiler is, the TypeGo -> Go transpilation might as well be similar (up to a constant factor) in speed to Go compilation itself.

I'd give it a try. As a highly enthusiastic Go programmer, a powerful TypeScript-like type system is something I'd welcome in Go with open arms.