From 97d831d008601d02d22cbd1b21c4b45809eabe10 Mon Sep 17 00:00:00 2001
From: Oli Scherer <git-spam-no-reply9815368754983@oli-obk.de>
Date: Tue, 4 Jul 2023 07:56:54 +0000
Subject: [PATCH] Show which type was not specialized on query cycle misuse

---
 compiler/rustc_query_system/src/values.rs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_query_system/src/values.rs b/compiler/rustc_query_system/src/values.rs
index b6e2cfa3dca..ce551078cc0 100644
--- a/compiler/rustc_query_system/src/values.rs
+++ b/compiler/rustc_query_system/src/values.rs
@@ -6,10 +6,13 @@ pub trait Value<Tcx: DepContext, D: DepKind>: Sized {
 }
 
 impl<Tcx: DepContext, T, D: DepKind> Value<Tcx, D> for T {
-    default fn from_cycle_error(tcx: Tcx, _: &[QueryInfo<D>]) -> T {
+    default fn from_cycle_error(tcx: Tcx, cycle: &[QueryInfo<D>]) -> T {
         tcx.sess().abort_if_errors();
         // Ideally we would use `bug!` here. But bug! is only defined in rustc_middle, and it's
         // non-trivial to define it earlier.
-        panic!("Value::from_cycle_error called without errors");
+        panic!(
+            "<{} as Value>::from_cycle_error called without errors: {cycle:#?}",
+            std::any::type_name::<T>()
+        );
     }
 }