From 688c857c560e60a98576afa52f0829d54164e180 Mon Sep 17 00:00:00 2001
From: Rich Kadel <richkadel@google.com>
Date: Sun, 21 Mar 2021 23:04:07 -0700
Subject: [PATCH] Improve error message for unassigned query provider

Fixes: 83122
---
 compiler/rustc_middle/src/ty/query/mod.rs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_middle/src/ty/query/mod.rs b/compiler/rustc_middle/src/ty/query/mod.rs
index 48e777f7158fd..c170858ba85a1 100644
--- a/compiler/rustc_middle/src/ty/query/mod.rs
+++ b/compiler/rustc_middle/src/ty/query/mod.rs
@@ -217,8 +217,11 @@ macro_rules! define_callbacks {
             fn default() -> Self {
                 Providers {
                     $($name: |_, key| bug!(
-                        "`tcx.{}({:?})` unsupported by its crate",
-                         stringify!($name), key
+                        "`tcx.{}({:?})` unsupported by its crate; \
+                         perhaps the `{}` query was never assigned a provider function",
+                        stringify!($name),
+                        key,
+                        stringify!($name),
                     ),)*
                 }
             }