Using `mod` with `?expand` can cause errors

[ChaiTRex]

I made a macro on the Playground (https://play.rust-lang.org/?edition=2024&gist=c97b5c5556702f39458f76c8be1b41bf), where expanding the macro in it worked fine with a few warnings but no errors. However, Ferris seems to wrap everything in fn main() {, and so using mod with it can give errors:

Request:

?expand ```rust
#[derive(PartialEq)]
pub struct Domain;

mod UILayout_template_asset_shelf_popover_icon {
    use super::Domain;

    pub const NONE: Domain = Domain;
    pub const CHAR_NOT_DEF: Domain = Domain;
}

macro_rules! thingy {
    ($val:ident, $prefix:ident : $($variant_name:ident,)*) => {
        match $val {
            $(
                $prefix :: $variant_name => stringify!($variant_name),
            )*
        }
    };
}

fn from(val: Domain) -> &'static str {
    thingy!(val, UILayout_template_asset_shelf_popover_icon:
        NONE,
        CHAR_NOT_DEF,
    )
}
```

Response:

error[E0432]: unresolved import `super::Domain`
 --> src/main.rs:6:9
  |
6 |     use super::Domain;
  |         ^^^^^^^^^^^^^ no `Domain` in the root
  |
help: a similar name exists in the module
  |
6 -     use super::Domain;
6 +     use super::main;
  |
help: consider importing one of these items instead
  |
6 -     use super::Domain;
6 +     use postgres::types::Kind::Domain;
  |
6 -     use super::Domain;
6 +     use postgres_types::Kind::Domain;
  |
6 -     use super::Domain;
6 +     use psl_types::Domain;
  |
6 -     use super::Domain;
6 +     use publicsuffix::Domain;
  |
  = and 4 other candidates

For more information about this error, try `rustc --explain E0432`.
error: could not compile `playground` (bin "playground") due to 1 previous error

pub struct Domain;
#[automatically_derived]
impl ::core::marker::StructuralPartialEq for Domain { }
#[automatically_derived]
impl ::core::cmp::PartialEq for Domain {
    #[inline]
    fn eq(&self, other: &Domain) -> bool { true }
}

mod UILayout_template_asset_shelf_popover_icon {
    use super::Domain;

    pub const NONE: Domain = Domain;
    pub const CHAR_NOT_DEF: Domain = Domain;

Output too large. Playground link: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2024&gist=d779e1c226455f3bdaecafd00f2c2365

[HomelikeBrick42]

You can put your own fn main() {} at the bottom to make the bot not wrap everything in its own main function (even #[cfg(false)] fn main() {} works because the bot just uses syn to parse the code to see if there is a function called main)