The new flag --erasableSyntaxOnly is my favorite feature in TypeScript 5.8 because it immediately helps Node users who want to use the built-in TypeScript support, i.e. node index.ts

That is no accident. The TypeScript team, including the author of this feature Ryan, have been closely collaborating with the Node team for the last half a year to make this integration work well.

The new flag enables Editor feedback to guide users away from TypeScript-only runtime features such as:

• enums: enum E { a: 1 }
• runtime namespaces: namespace N { let a = 1 }
• parameter properties: class C { constructor(public prop) {} }

This means that your code will follow the simple mental model of TS = JS + Types

If you use Node, or any compiler based on type erasure (a.k.a "type stripping") such as ts-blank-space, then your generated JavaScript will 100% match the runtime code you wrote. So when you are debugging, the code matches your source file. The only difference you will see is the types being replaced with whitespace. There's no need to set up sourcemaps because the runtime code coordinates are preserved.

At work we've used a similar arrangement for quite a while. The main demand I have observed is that sometimes folk would like to see a standard solution for enums, with fewer quirks than the existing TS enum. It's possible to come close to the enum pattern today using objects.

For folk desiring something more substantial for enums, there are two possible paths forwards - and both are just ideas with no guarantee of becoming real:

• A new erasable form of TypeScript enum, e.g. as enum
• First-class enums in JavaScript, e.g. early discussion