feat: rbe 1.2.2.1: test case list w/ activity

1-hello-world/formatted-printing/list-display/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "list-display"
+version = "0.1.0"

1-hello-world/formatted-printing/list-display/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "list-display"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

1-hello-world/formatted-printing/list-display/src/main.rs

@@ -0,0 +1,29 @@
+// Import the `fmt` module.
+use std::fmt;
+
+// Define a structuree named `List` containing a `Vec`.
+struct List(Vec<i32>);
+
+impl fmt::Display for List {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        // Create a reference to the Vec<i32> stored in the List struct.
+        let vec = &self.0;
+
+        write!(f, "[")?;
+
+        // Iterate over `v` in `vec` while enumerating the iteration
+        // index in `index`.
+        for (index, v) in vec.iter().enumerate() {
+            if index != 0 { write!(f, ", ")?; }
+            write!(f, "{index}: {v}")?;
+        }
+
+        // Close the opend bracket and return a fmt::Result value.
+        write!(f, "]")
+    }
+}
+
+fn main() {
+    let v = List(vec![1, 2, 3]);
+    println!("{}", v);
+}