[class.union.anon] Are lambda expressions disallowed in anonymous unions?

[hubert-reinterpretcast]

Full name of submitter (unless configured in github; will be published with the issue): Hubert Tong

Reference (section label): class.union.anon

Link to reflector thread (if any): N/A

Issue description:
https://eel.is/c++draft/class.union.anon#1.sentence-3 says:

Nested types, anonymous unions, and functions shall not be declared within an anonymous union.

A lambda expression declares a closure type (https://eel.is/c++draft/expr.prim.lambda#closure-2).

Does that mean that lambda expressions are disallowed in anonymous unions?

Only EDG generates a diagnostic for https://godbolt.org/z/xf96EbKTn:

static union {
  int x = [] { return 42; }();
};

Suggested resolution:

Nested types, including closure types and anonymous unions, and functions shall not be declared within an anonymous union.

[Eisenwave]

I think the wording is fairly clear on this, although it is surprising that IILEs wouldn't be okay.

I doubt that the current behavior is intentional, and maybe a better approach would be to ask EWG to exclude closure types, effectively standardizing what Clang, GCC, and MSVC already do. If we don't do that, the resolution looks correct.