From 93a17c8aeade5ea650e6dc5c047d895e3afaa091 Mon Sep 17 00:00:00 2001
From: lcnr <rust@lcnr.de>
Date: Tue, 4 Oct 2022 14:18:11 +0200
Subject: [PATCH] missing value to delay_span_bug

---
 compiler/rustc_ty_utils/src/instance.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs
index fa1dc90e4a24b..81ca8b646fff1 100644
--- a/compiler/rustc_ty_utils/src/instance.rs
+++ b/compiler/rustc_ty_utils/src/instance.rs
@@ -171,9 +171,13 @@ fn resolve_associated_item<'tcx>(
                 return Ok(None);
             }
 
-            // If the item does not have a value, then we cannot return an instance.
+            // Any final impl is required to define all associated items.
             if !leaf_def.item.defaultness(tcx).has_value() {
-                return Ok(None);
+                let guard = tcx.sess.delay_span_bug(
+                    tcx.def_span(leaf_def.item.def_id),
+                    "missing value for assoc item in impl",
+                );
+                return Err(guard);
             }
 
             let substs = tcx.erase_regions(substs);