Initializer Containing arrow containing arguments

[bakkot]

The rule which prevents initializers from referring to arguments uses Contains, which does not descend into arrow functions except for new.target, super, and this.

It should be an early error, I think. Including recursively - we should disallow

class A {
  a = b => c => { return arguments; };
}

Not entirely sure how to spec it though.

[bakkot]

As a strawman, we could add a new algorithm ContainsArguments which descends into everything except FunctionDeclaration/Expression and ClassBody (taking advantage of chain productions to minimize the amount of spec text necessary). I'll try to spec that to see how it looks.

[bakkot]

Also, strictly speaking, I don't think Contains can be used for something as specific as 'an IdentifierReference whose StringValue is "arguments".' It takes a terminal or nonterminal as an argument; I don't know if it can be used to look for nonterminals with specific properties.

[littledan]

Thanks for following up here; this seems to be a continuation of https://github.com/tc39/proposal-class-public-fields/pull/41/files/d2faa6128850b575057f727075256d0b95d5322f#r72339498 . Sorry for dropping the ball on that issue.