Add a test to reproduce ICE

tests/incremental/print-dep-node-cycle.rs

@@ -0,0 +1,25 @@
+//@ compile-flags: -Z query-dep-graph
+//@ revisions: rpass1
+
+// Exercises a debug-assertions-only query cycle that when printing a valtree const in
+// a dep node's debug representation, we end up invoking a query that also has a valtree
+// const in its dep node's debug representation, which leads to a cycle (and ICE, since
+// deps are not tracked when printing dep nodes' debug representations).
+
+#![feature(adt_const_params)]
+
+use std::marker::ConstParamTy;
+
+#[derive(Debug, ConstParamTy, PartialEq, Eq)]
+enum Foo {
+    A1,
+}
+
+#[inline(never)]
+fn hello<const F: Foo>() {
+    println!("{:#?}", F);
+}
+
+fn main() {
+    hello::<{ Foo::A1 }>();
+}