#[serde(rename)] and #[serde(alias)] should be forbidden on variants of untagged enums

[Mingun]

Both attributes does nothing and just confuse users:

#[derive(serde::Deserialize)]
#[serde(untagged)]
pub enum Untagged {
    #[serde(rename = "unit", alias = "_1")]
    Unit,

    #[serde(rename = "newtype", alias = "_2")]
    Newtype(u32),

    #[serde(rename = "tuple", alias = "_3")]
    Tuple(u32, u32),

    #[serde(rename = "struct", alias = "_4")]
    Struct { a: u32 },
}

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=bc78b6a4d132a2c255db120036d7fa42

Instead an error should be emitted that such attributes (maybe some other too!) does nothing and not allowed for untagged enums.