1use proc_macro::TokenStream;
 2use quote::quote;
 3use syn::{
 4    parse_macro_input, parse_quote, DeriveInput, GenericParam, Generics, Ident, WhereClause,
 5};
 6
 7pub fn derive_into_element(input: TokenStream) -> TokenStream {
 8    let ast = parse_macro_input!(input as DeriveInput);
 9    let type_name = ast.ident;
10
11    let placeholder_view_generics: Generics = parse_quote! { <V: 'static> };
12    let placeholder_view_type_name: Ident = parse_quote! { V };
13    let view_type_name: Ident;
14    let impl_generics: syn::ImplGenerics<'_>;
15    let type_generics: Option<syn::TypeGenerics<'_>>;
16    let where_clause: Option<&'_ WhereClause>;
17
18    match ast.generics.params.iter().find_map(|param| {
19        if let GenericParam::Type(type_param) = param {
20            Some(type_param.ident.clone())
21        } else {
22            None
23        }
24    }) {
25        Some(type_name) => {
26            view_type_name = type_name;
27            let generics = ast.generics.split_for_impl();
28            impl_generics = generics.0;
29            type_generics = Some(generics.1);
30            where_clause = generics.2;
31        }
32        _ => {
33            view_type_name = placeholder_view_type_name;
34            let generics = placeholder_view_generics.split_for_impl();
35            impl_generics = generics.0;
36            type_generics = None;
37            where_clause = generics.2;
38        }
39    }
40
41    impl_into_element(
42        &impl_generics,
43        &view_type_name,
44        &type_name,
45        &type_generics,
46        &where_clause,
47    )
48    .into()
49}
50
51pub fn impl_into_element(
52    impl_generics: &syn::ImplGenerics<'_>,
53    view_type_name: &Ident,
54    type_name: &Ident,
55    type_generics: &Option<syn::TypeGenerics<'_>>,
56    where_clause: &Option<&WhereClause>,
57) -> proc_macro2::TokenStream {
58    quote! {
59        impl #impl_generics gpui2::element::IntoElement<#view_type_name> for #type_name #type_generics
60        #where_clause
61        {
62            type Element = Self;
63
64            fn into_element(self) -> Self {
65                self
66            }
67        }
68    }
69}