Rollup merge of #51921 - japaric:panic-impl-error, r=nagisa

improve the error message when `#[panic_implementation]` is missing

closes #51341

r? @nagisa
cc @phil-opp

1 files changed, 7 insertions, 3 deletions

diff --git a/src/librustc/middle/weak_lang_items.rs b/src/librustc/middle/weak_lang_items.rs
index 1d147eef054..180e75df1a6 100644
--- a/src/librustc/middle/weak_lang_items.rs
+++ b/src/librustc/middle/weak_lang_items.rs
@@ -112,9 +112,13 @@ fn verify<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         if missing.contains(&lang_items::$item) &&
            !whitelisted(tcx, lang_items::$item) &&
            items.$name().is_none() {
-            tcx.sess.err(&format!("language item required, but not found: `{}`",
-                                  stringify!($name)));
-
+            if lang_items::$item == lang_items::PanicImplLangItem {
+                tcx.sess.err(&format!("`#[panic_implementation]` function required, \
+                                        but not found"));
+            } else {
+                tcx.sess.err(&format!("language item required, but not found: `{}`",
+                                        stringify!($name)));
+            }
         }
     )*
 }