chore: checkpoint before Python removal

vendor/darling/examples/expr_with.rs

@@ -0,0 +1,26 @@
+use darling::{util::parse_expr, FromDeriveInput, FromMeta};
+use syn::{parse_quote, Expr};
+
+#[derive(FromDeriveInput)]
+#[darling(attributes(demo))]
+pub struct Receiver {
+    #[darling(with = parse_expr::preserve_str_literal, map = Some)]
+    example1: Option<Expr>,
+    #[darling(
+        // A closure can be used in lieu of a path.
+        with = |m| Ok(String::from_meta(m)?.to_uppercase()),
+        default
+    )]
+    example2: String,
+}
+
+fn main() {
+    let input = Receiver::from_derive_input(&parse_quote! {
+        #[demo(example1 = test::path, example2 = "hello")]
+        struct Example;
+    })
+    .unwrap();
+
+    assert_eq!(input.example1, Some(parse_quote!(test::path)));
+    assert_eq!(input.example2, "HELLO".to_string());
+}