generics1 rewrite and solution

exercises/14_generics/generics1.rs

@@ -1,7 +1,18 @@
-// This shopping list program isn't compiling! Use your knowledge of generics to
-// fix it.
+// `Vec<T>` is generic over the type `T`. In most cases, the compiler is able to
+// infer `T`, for example after pushing a value with a concrete type to the vector.
+// But in this exercise, the compiler needs some help through a type annotation.
 
 fn main() {
-    let mut shopping_list: Vec<?> = Vec::new();
-    shopping_list.push("milk");
+    // TODO: Fix the compiler error by annotating the type of the vector
+    // `Vec<T>`. Choose `T` as some integer type that can be created from
+    // `u8` and `i8`.
+    let mut numbers = Vec::new();
+
+    // Don't change the lines below.
+    let n1: u8 = 42;
+    numbers.push(n1.into());
+    let n2: i8 = -1;
+    numbers.push(n2.into());
+
+    println!("{numbers:?}");
 }