bevyengine/bevy · error · syn::Error

cannot use parenthesized type as remote type

Error message

cannot use parenthesized type as remote type

What it means

Compile-time syn error from RemoteType::as_expr_path: the remote type's path is parenthesized (e.g. Fn() -> Foo), so it cannot be converted into an expression path usable by the generated remote-reflect code.

Source

Thrown at crates/bevy_reflect/derive/src/remote.rs:471

    pub fn type_path(&self) -> &'a TypePath {
        self.path
    }

    /// Attempts to convert the [type path](TypePath) of this remote type into an [expression path](ExprPath).
    ///
    /// For example, this would convert `foo::Bar<T>` into `foo::Bar::<T>` to be used as part of an expression.
    ///
    /// This will return an error for types that are parenthesized, such as in `Fn() -> Foo`.
    pub fn as_expr_path(&self) -> Result<ExprPath, syn::Error> {
        let mut expr_path = self.path.clone();
        if let Some(segment) = expr_path.path.segments.last_mut() {
            match &mut segment.arguments {
                PathArguments::None => {}
                PathArguments::AngleBracketed(arg) => {
                    arg.colon2_token = Some(PathSep::default());
                }
                PathArguments::Parenthesized(arg) => {
                    return Err(syn::Error::new(
                        arg.span(),
                        "cannot use parenthesized type as remote type",
                    ))
                }
            }
        }

        Ok(ExprPath {
            path: expr_path.path,
            qself: expr_path.qself,
            attrs: Vec::new(),
        })
    }
}

/// Metadata from the arguments defined in the `reflect_remote` attribute.
///
/// The syntax for the arguments is: `#[reflect_remote(REMOTE_TYPE_PATH)]`.

View on GitHub (pinned to 396ca72708)

Solutions

1. Use a non-parenthesized type path for the remote type
2. Wrap the parenthesized type in a newtype and reflect that instead

When it happens

Trigger: Thrown at crates/bevy_reflect/derive/src/remote.rs:471 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of bevyengine/bevy@396ca72708 (2026-08-20). Data as JSON: /api/errors/84ffc4d22507ca3b. Report an issue: GitHub.