Add support for character constants

src/engine.rs

@@ -636,6 +636,7 @@ impl Engine {
         match *expr {
             Expr::IntConst(i) => Ok(Box::new(i)),
             Expr::StringConst(ref s) => Ok(Box::new(s.clone())),
+            Expr::CharConst(ref c) => Ok(Box::new(c.clone())),
             Expr::Identifier(ref id) => {
                 for &mut (ref name, ref mut val) in &mut scope.iter_mut().rev() {
                     if *id == *name {
@@ -1029,6 +1030,30 @@ fn test_number_literal() {
     }
 }
 
+#[test]
+fn test_chars() {
+    let mut engine = Engine::new();
+
+    if let Ok(result) = engine.eval::<char>("'y'") {
+        assert_eq!(result, 'y');
+    }
+    else {
+        assert!(false);
+    }
+
+    if let Ok(result) = engine.eval::<char>("'\\u2764'") {
+        assert_eq!(result, '❤');
+    }
+    else {
+        assert!(false);
+    }
+
+    match engine.eval::<char>("''") {
+        Err(_) => (),
+        _ => assert!(false)
+    }
+}
+
 #[test]
 fn test_ops() {
     let mut engine = Engine::new();