Enum declarations should consistently disallow computed keys

Bug Report

🔎 Search Terms

• Computed property names are not allowed in enums
• enum declaration computed

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about enums

⏯ Playground Link

Playground link with relevant code

💻 Code

let y = "y";
type z = "z";

enum Foo {
    ['x'],
    [{}],
    [y],
    [z]
}

🙁 Actual behavior

TS reports Computed property names are not allowed in enums. for [{}], [y] and [z], while it allows ['x'] (in contraddiction with the error message).

🙂 Expected behavior

All of them should be an error, for the reason reported by the error.

📚 Context

This came up at https://github.com/babel/babel/issues/12683: we can implement the current TS behavior in Babel, but I'd first like to check if TS is expected to report an error for ['x'].

Reproduce the behavior from the linked TypeScript Playground using the enum sample with ['x'], [{}], [y], and [z]. Trace the enum computed-property diagnostic from that example; done means all four declarations consistently produce the reported error, with coverage for the demonstrated cases.