from_type_param_default.rs

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use darling::FromTypeParam;

use syn::{parse_quote, DeriveInput, GenericParam, TypeParam};

#[derive(Default, FromTypeParam)]

#[darling(attributes(lorem), default)]

struct Lorem {

    foo: bool,

    bar: Option<String>,

    default: Option<syn::Type>,

fn extract_type(param: &GenericParam) -> &TypeParam {

    match *param {

        GenericParam::Type(ref ty) => ty,

        _ => unreachable!("Not a type param"),

#[test]

#[allow(clippy::bool_assert_comparison)]

fn expand_many() {

    let di: DeriveInput = parse_quote! {

        struct Baz<

            #[lorem(foo)] T,

            #[lorem(bar = "x")] U: Eq + ?Sized,

            #[lorem(foo = false)] V = (),

        >(T, U, V);

};

    let params = di.generics.params;

        let ty = extract_type(&params[0]);

        let lorem = Lorem::from_type_param(ty).unwrap();

        assert_eq!(lorem.foo, true);

        assert_eq!(lorem.bar, None);

        let ty = extract_type(&params[1]);

        let lorem = Lorem::from_type_param(ty).unwrap();

        assert_eq!(lorem.foo, false);

        assert_eq!(lorem.bar, Some("x".to_string()));

        assert!(lorem.default.is_none());

        let ty = extract_type(&params[2]);

        let lorem = Lorem::from_type_param(ty).unwrap();

        assert_eq!(lorem.foo, false);

        assert_eq!(lorem.bar, None);

        assert!(lorem.default.is_some());