Add tests for if-then-else before adding parsing

src/compiler/ast.rs

@@ -1,4 +1,3 @@
-#[expect(dead_code)]
 #[derive(Debug, PartialEq)]
 pub enum Expression<'source> {
     IntLiteral(u32),
@@ -9,4 +8,9 @@ pub enum Expression<'source> {
         &'source str,
         Box<Expression<'source>>,
     ),
+    Conditional(
+        Box<Expression<'source>>,
+        Box<Expression<'source>>,
+        Option<Box<Expression<'source>>>,
+    ),
 }

src/compiler/parser.rs

@@ -324,6 +324,118 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_if_then() {
+        let result = parse(&vec![
+            new_id("if"),
+            new_int("1"),
+            new_id("+"),
+            new_int("2"),
+            new_id("then"),
+            new_int("3"),
+        ]);
+        assert_eq!(
+            result,
+            Conditional(
+                Box::new(BinaryOp(
+                    Box::new(IntLiteral(1)),
+                    "+",
+                    Box::new(IntLiteral(2))
+                )),
+                Box::new(IntLiteral(3)),
+                None,
+            )
+        );
+    }
+
+    #[test]
+    fn test_if_then_else() {
+        let result = parse(&vec![
+            new_id("if"),
+            new_id("a"),
+            new_id("then"),
+            new_id("b"),
+            new_id("+"),
+            new_id("c"),
+            new_id("else"),
+            new_int("1"),
+            new_id("*"),
+            new_int("2"),
+        ]);
+        assert_eq!(
+            result,
+            Conditional(
+                Box::new(Identifier("a")),
+                Box::new(BinaryOp(
+                    Box::new(Identifier("b")),
+                    "+",
+                    Box::new(Identifier("c")),
+                )),
+                Some(Box::new(BinaryOp(
+                    Box::new(IntLiteral(1)),
+                    "*",
+                    Box::new(IntLiteral(2)),
+                )))
+            )
+        );
+    }
+
+    #[test]
+    fn test_embedded_if_then_else() {
+        let result = parse(&vec![
+            new_int("1"),
+            new_id("+"),
+            new_id("if"),
+            new_id("true"),
+            new_id("then"),
+            new_int("2"),
+            new_id("else"),
+            new_int("3"),
+        ]);
+        assert_eq!(
+            result,
+            BinaryOp(
+                Box::new(IntLiteral(1)),
+                "+",
+                Box::new(Conditional(
+                    Box::new(BoolLiteral(true)),
+                    Box::new(IntLiteral(2)),
+                    Some(Box::new(IntLiteral(3)))
+                ))
+            )
+        );
+    }
+
+    #[test]
+    fn test_nested_if_then_else() {
+        // if true then if false then 1 else 2 else 3
+        let result = parse(&vec![
+            new_id("if"),
+            new_id("true"),
+            new_id("then"),
+            new_id("if"),
+            new_id("false"),
+            new_id("then"),
+            new_int("1"),
+            new_id("else"),
+            new_int("2"),
+            new_id("else"),
+            new_int("3"),
+        ]);
+        assert_eq!(
+            result,
+            Conditional(
+                Box::new(BoolLiteral(true)),
+                Box::new(Conditional(
+                    Box::new(BoolLiteral(false)),
+                    Box::new(IntLiteral(1)),
+                    Some(Box::new(IntLiteral(2)))
+                )),
+                Some(Box::new(IntLiteral(3)))
+            )
+        );
+    }
+
     #[test]
     #[should_panic]
     fn test_parenthesized_mismatched() {
@@ -337,6 +449,12 @@ mod tests {
         ]);
     }
 
+    #[test]
+    #[should_panic]
+    fn test_if_no_then() {
+        parse(&vec![new_id("if"), new_id("true")]);
+    }
+
     #[test]
     #[should_panic]
     fn test_empty() {