Class-fields in TypeScript have [[Set]] semantics. Foresee code breaking when JavaScript projects convert to TypeScript (or vice versa), and the pain caused from hard-to-find bugs, because of JavaScript class-fields using [[Define]] semantics.

I know this has been discussed in other threads, but I thought I'd open an official issue for it.

EDIT: Why not add a define keyword:

class Foo {
  foo = 'foo' // uses [[Set]] semantics
  define bar = 'bar' // uses [[Define]] semantics
}

Honestly, it would make most people (talking about end users who develop products, not language designers or implementors) happy.