feat: SCC analysis (thunk capture WIP)

src/engine/test.rs

@@ -16,7 +16,9 @@ use super::eval;
 
 #[inline]
 fn test_expr(expr: &str, expected: Value) {
-    let (downgraded, _) = downgrade(rnix::Root::parse(expr).tree().expr().unwrap()).unwrap();
+    println!("{expr}");
+    let downgraded = downgrade(rnix::Root::parse(expr).tree().expr().unwrap()).unwrap();
+    println!("{downgraded:?}");
     assert_eq!(eval(downgraded).unwrap(), expected);
 }
 
@@ -148,6 +150,13 @@ fn test_attrs() {
             symbol!("a") => int!(1)
         },
     );
+    test_expr(
+        "rec { a = 1; b = a; }",
+        attrs! {
+            symbol!("a") => int!(1),
+            symbol!("b") => thunk!()
+        },
+    );
     test_expr("{ a = 1; }.a", int!(1));
     test_expr("{ a = 1; }.b or 1", int!(1));
     test_expr(
@@ -193,7 +202,7 @@ fn test_let() {
 fn test_func() {
     test_expr("(x: x) 1", int!(1));
     test_expr("(x: x) (x: x) 1", int!(1));
-    test_expr("(x: y: x + y) 1 1", int!(2));
+    test_expr("(x: y: x / y) 1 2", int!(0));
     test_expr("({ x, y }: x + y) { x = 1; y = 2; }", int!(3));
     test_expr("({ x, y, ... }: x + y) { x = 1; y = 2; z = 3; }", int!(3));
     test_expr(