Add failing test

tests/incremental/track-deps-in-new-solver.rs

@@ -0,0 +1,25 @@
+//@ revisions: cfail1 cfail2
+
+//@ compile-flags: -Znext-solver
+//@ check-pass
+
+pub trait Future {
+    type Error;
+    fn poll() -> Self::Error;
+}
+
+struct S;
+impl Future for S {
+    type Error = Error;
+    fn poll() -> Self::Error {
+        todo!()
+    }
+}
+
+#[cfg(cfail1)]
+pub struct Error(());
+
+#[cfg(cfail2)]
+pub struct Error();
+
+fn main() {}