Add support for class static block

[Kingwl]

Fixes #43012

• type definitions
• factory
• parser
• binder
• checker
  • grammar
  • use before assignment
• transformer
• emitter
• visitor
• tests

[Kingwl]

tc39/proposal-class-static-block#27

[rbuckton]

Well.... I think this one is depends on #42986 too....

Correction: This will depend on #42458, which includes everything in #42986.

[Kingwl]

Still confused with the boundary.

[rbuckton]

I'm still reviewing #42458, and we've been discussing the fact that this in static fields is currently disallowed, which would effect the order of emit. Also, the static block proposal itself is layered on the static features and class private proposal, so its important that evaluation order is correct:

class C {
  static #x;
  static {
    this.#x; // ok
    this.#y; // error, #y not yet initialized
  }
  static #y;
  static {
    this.#x; // ok
    this.#y; // ok
  }
}

Either way, I'll still be happy to review when you think this is ready.

[Kingwl]

Okay, thanks a lot.

BTW, there's another PR to allow this in static context.

Actually, I'm confused with the function boundary in the specification(as i said in class static block repo).

[Kingwl]

tc39/proposal-class-static-block#27

This one.( Sorry I'm on mobile phone )

[rbuckton]

I addressed your comment in that issue. The TL;DR is this:

• Class bodies are not function boundaries (ClassHeritage and ComputedPropertyName are evaluated in the class's containing scope), so an await in either position in a class static block would be an error.
• FormalParameters, ArrowFormalParameters, and AsyncArrowBindingIdentifier are function boundaries, since parameter initializers are evaluated when the function is called.
• FunctionBody, GeneratorBody, AsyncGeneratorBody, AsyncFunctionBody, ConciseBody, and AsyncConciseBody are function boundaries.
• A ClassStaticBlock is a function boundary, but is also a class static block (so await as an identifier would be an error).
• Static/instance field initializers are function boundaries, as an implicit function is created that wraps the initializer to provide the correct this binding and access the lexical class binding.

[Kingwl]

I think I'd better to work based #42458. Even It's not been merged.

[Kingwl]

Close for #43308.