bindex: contained fjall code

struct_iterable/struct_iterable_derive/src/lib.rs

@@ -0,0 +1,88 @@
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{parse_macro_input, Data, DeriveInput, Fields};
+
+/// The `Iterable` proc macro.
+///
+/// Deriving this macro for your struct will make it "iterable". An iterable struct allows you to iterate over its fields, returning a tuple containing the field name as a static string and a reference to the field's value as `dyn Any`.
+///
+/// # Limitations
+///
+/// - Only structs are supported, not enums or unions.
+/// - Only structs with named fields are supported.
+///
+/// # Usage
+///
+/// Add the derive attribute (`#[derive(Iterable)]`) above your struct definition.
+///
+/// ```
+/// use struct_iterable::Iterable;
+///
+/// #[derive(Iterable)]
+/// struct MyStruct {
+///     field1: i32,
+///     field2: String,
+/// }
+/// ```
+///
+/// You can now call the `iter` method on instances of your struct to get an iterator over its fields:
+///
+/// ```
+/// let my_instance = MyStruct {
+///     field1: 42,
+///     field2: "Hello, world!".to_string(),
+/// };
+///
+/// for (field_name, field_value) in my_instance.iter() {
+///     println!("{}: {:?}", field_name, field_value);
+/// }
+/// ```
+#[proc_macro_derive(Iterable)]
+pub fn derive_iterable(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+
+    let struct_name = input.ident;
+    let fields = match input.data {
+        Data::Struct(data_struct) => match data_struct.fields {
+            Fields::Named(fields_named) => fields_named.named,
+            _ => panic!("Only structs with named fields are supported"),
+        },
+        _ => panic!("Only structs are supported"),
+    };
+
+    let fields_iter = fields.iter().map(|field| {
+        let field_ident = &field.ident;
+        let field_name = field_ident.as_ref().unwrap().to_string();
+        quote! {
+            (#field_name, &(self.#field_ident) as &dyn std::any::Any)
+        }
+    });
+
+    let fields_iter_mut = fields.iter().map(|field| {
+        let field_ident = &field.ident;
+        let field_name = field_ident.as_ref().unwrap().to_string();
+        quote! {
+            (#field_name, &mut (self.#field_ident) as &mut dyn std::any::Any)
+        }
+    });
+
+    let expanded = quote! {
+        impl Iterable for #struct_name {
+            fn iter<'a>(&'a self) -> std::vec::IntoIter<(&'static str, &'a dyn std::any::Any)> {
+                vec![
+                    #(#fields_iter),*
+                ].into_iter()
+            }
+
+            fn iter_mut<'a>(&'a mut self) -> std::vec::IntoIter<(&'static str, &'a mut dyn std::any::Any)> {
+                vec![
+                    #(#fields_iter_mut),*
+                ].into_iter()
+            }
+        }
+    };
+
+    TokenStream::from(expanded)
+}