Checkpoint

crates/gpui2_macros/src/derive_into_element.rs

@@ -0,0 +1,69 @@
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{
+    parse_macro_input, parse_quote, DeriveInput, GenericParam, Generics, Ident, WhereClause,
+};
+
+pub fn derive_into_element(input: TokenStream) -> TokenStream {
+    let ast = parse_macro_input!(input as DeriveInput);
+    let type_name = ast.ident;
+
+    let placeholder_view_generics: Generics = parse_quote! { <V: 'static> };
+    let placeholder_view_type_name: Ident = parse_quote! { V };
+    let view_type_name: Ident;
+    let impl_generics: syn::ImplGenerics<'_>;
+    let type_generics: Option<syn::TypeGenerics<'_>>;
+    let where_clause: Option<&'_ WhereClause>;
+
+    match ast.generics.params.iter().find_map(|param| {
+        if let GenericParam::Type(type_param) = param {
+            Some(type_param.ident.clone())
+        } else {
+            None
+        }
+    }) {
+        Some(type_name) => {
+            view_type_name = type_name;
+            let generics = ast.generics.split_for_impl();
+            impl_generics = generics.0;
+            type_generics = Some(generics.1);
+            where_clause = generics.2;
+        }
+        _ => {
+            view_type_name = placeholder_view_type_name;
+            let generics = placeholder_view_generics.split_for_impl();
+            impl_generics = generics.0;
+            type_generics = None;
+            where_clause = generics.2;
+        }
+    }
+
+    impl_into_element(
+        &impl_generics,
+        &view_type_name,
+        &type_name,
+        &type_generics,
+        &where_clause,
+    )
+    .into()
+}
+
+pub fn impl_into_element(
+    impl_generics: &syn::ImplGenerics<'_>,
+    view_type_name: &Ident,
+    type_name: &Ident,
+    type_generics: &Option<syn::TypeGenerics<'_>>,
+    where_clause: &Option<&WhereClause>,
+) -> proc_macro2::TokenStream {
+    quote! {
+        impl #impl_generics playground::element::IntoElement<#view_type_name> for #type_name #type_generics
+        #where_clause
+        {
+            type Element = Self;
+
+            fn into_element(self) -> Self {
+                self
+            }
+        }
+    }
+}