Design Meeting Notes, 1/21/2025

[DanielRosenwasser]

Flag for Erasable Syntax Only

• Flag in light of strippable type support for TypeScript in Node.js.
• --erasableSyntaxOnly
• What is it?
  • No enums, namespaces, parameter properties.
• Allow all these in ambient contexts (declare keywords).
• Can we get it in in the next week?
  • Probably.
• --verbatimModuleSyntax?
  • Compilers can do this independently?
  • Module elision is not in line with what Node itself supports.
  • Also, purists might not really be into module elision in the first place.
  • Unclear
• What about uninstantiated namespaces?
  • They should be allowed...but Node.js disallows them.

  • // uninstantiated - should be allowed, currently is NOT in Node.js ⚠️
    export namespace foo1 {
        export interface I {}
    }
    
    // ambient - should be allowed, currently is in Node.js
    export declare namespace foo2 {
        export interface I {}
    }
    
    // instantiated - should *not* be allowed, and is currently disallowed in Node.js
    export namespace foo3 {
        export interface I {}
    
        1 + 2;
    }

  • Arguable that being forced to write declare is a bit of a footgun to force everyone to write: Tsconfig option to disallow features requiring transformations which are not supported by Node.js' --strip-types #59601 (comment)
    • Nice that declare makes it clear there's no JS
    • On the other hand, declare implies something is a little bit odd about the surrounding environment.
  • We think we'll allow uninstantiated namespaces, may restrict more later if we really made a mistake. New usage of this code is fairly low regardless.