add more tests

Author: stringhandler

src/lib.rs

@@ -1003,6 +1003,75 @@ fn main() {
             assert!(warning_names(prog).is_empty());
         }
 
+        #[test]
+        fn shadowed_outer_variable_unused_warns() {
+            // Outer `x` is never referenced; inner `x` shadows it and is used.
+            // Only the outer binding should warn.
+            let prog = r#"fn main() {
+    let x: u8 = 1;
+    let y: u8 = {
+        let x: u8 = 2;
+        x
+    };
+    assert!(jet::eq_8(y, 2))
+}"#;
+            let names = warning_names(prog);
+            assert_eq!(
+                names.len(),
+                1,
+                "Expected exactly one warning (outer x), got: {names:?}",
+            );
+            assert!(
+                matches!(&names[0], WarningName::UnusedVariable(id) if id.as_inner() == "x"),
+                "Expected UnusedVariable(x) for the outer binding, got: {:?}",
+                names,
+            );
+        }
+
+        #[test]
+        fn shadowed_inner_variable_unused_warns() {
+            // Outer `x` is used as the RHS of the inner binding.
+            // Inner `x` is never referenced after being bound, so it should warn.
+            let prog = r#"fn main() {
+    let x: u8 = 1;
+    let y: u8 = {
+        let x: u8 = x;
+        0
+    };
+    assert!(jet::eq_8(y, 0))
+}"#;
+            let names = warning_names(prog);
+            assert_eq!(
+                names.len(),
+                1,
+                "Expected exactly one warning (inner x), got: {names:?}",
+            );
+            assert!(
+                matches!(&names[0], WarningName::UnusedVariable(id) if id.as_inner() == "x"),
+                "Expected UnusedVariable(x) for the inner binding, got: {:?}",
+                names,
+            );
+        }
+
+        #[test]
+        fn outer_variable_used_after_inner_scope_no_warning() {
+            // `x` is bound in the outer scope, referenced after an inner block
+            // that binds a different name. Neither binding should warn.
+            let prog = r#"fn main() {
+    let x: u8 = 1;
+    let y: u8 = {
+        let z: u8 = 2;
+        z
+    };
+    let (_, sum): (bool, u8) = jet::add_8(x, y);
+    assert!(jet::eq_8(sum, 3))
+}"#;
+            assert!(
+                warning_names(prog).is_empty(),
+                "Expected no warnings when all variables are used",
+            );
+        }
+
         #[test]
         fn deny_warning_by_category_is_error() {
             use crate::WarnCategory;