variables defined using def in a let statement now escape local scope

test added as well.

tests/test_lib_control.rs

@@ -65,6 +65,26 @@ mod control_lib_tests {
         );
     }
 
+    #[test]
+    fn test_let_def_escapes_locals() {
+        let document1 = "(let (
+                           (temp 'hello')
+                           (temp (concat temp ' ' 'world')))
+                          (def global '' temp))";
+        let document2 = "global";
+        let result = "('hello world')";
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms).unwrap();
+        dynamic_stdlib(&mut syms).unwrap();
+        eval(&lex(&document1.to_string()).unwrap(), &mut syms).unwrap();
+        assert_eq!(
+            *eval(&lex(&document2.to_string()).unwrap(), &mut syms)
+                .unwrap()
+                .to_string(),
+            result.to_string(),
+        );
+    }
+
     #[test]
     fn test_let_multibody_evals() {
         let document = "(let ((temp '1')) temp (cons () temp '2'))";