fn render_binding_arg()

in starlark_derive/src/render.rs [299:349]

• 47 lines of code
• 8 McCabe index (conditional complexity)

fn render_binding_arg(arg: &StarArg) -> TokenStream {
    let span = arg.span;
    let name = &arg.name;
    let name_str = ident_string(name);
    let ty = &arg.ty;

    let source = match arg.source {
        StarArgSource::This => quote_spanned! {span=> __this},
        StarArgSource::Argument(i) => quote_spanned! {span=> __args[#i].get()},
        StarArgSource::Required(i) => quote_spanned! {span=> Some(__required[#i])},
        StarArgSource::Optional(i) => quote_spanned! {span=> __optional[#i]},
        ref s => unreachable!("unknown source: {:?}", s),
    };

    // Rust doesn't have powerful enough nested if yet
    let next = if arg.is_this() {
        quote_spanned! { span=> starlark::eval::Arguments::check_this(#source)? }
    } else if arg.is_option() {
        assert!(
            arg.default.is_none(),
            "Can't have Option argument with a default, for `{}`",
            name_str
        );
        quote_spanned! { span=> starlark::eval::Arguments::check_optional(#name_str, #source)? }
    } else if !arg.is_value() && arg.default.is_some() {
        let default = arg
            .default
            .as_ref()
            .unwrap_or_else(|| unreachable!("Checked on the line above"));
        quote_spanned! { span=>
            {
                // Combo
                #[allow(clippy::manual_unwrap_or)]
                #[allow(clippy::unnecessary_lazy_evaluations)]
                #[allow(clippy::redundant_closure)]
                let x = starlark::eval::Arguments::check_optional(#name_str, #source)?.unwrap_or_else(|| #default);
                x
            }
        }
    } else {
        quote_spanned! { span=> starlark::eval::Arguments::check_required(#name_str, #source)? }
    };

    let mutability = mut_token(arg.mutable);
    let attrs = &arg.attrs;
    quote_spanned! {
        span=>
        #( #attrs )*
        let #mutability #name: #ty = #next;
    }
}