From 0bf75fbfc8812ed0c7dc827def29c9d65a438eac Mon Sep 17 00:00:00 2001
From: bjorn3 <bjorn3@users.noreply.github.com>
Date: Sat, 12 Dec 2020 16:51:11 +0100
Subject: [PATCH 1/2] Use better symbol names for the drop glue

---
 compiler/rustc_symbol_mangling/src/legacy.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/compiler/rustc_symbol_mangling/src/legacy.rs b/compiler/rustc_symbol_mangling/src/legacy.rs
index eba8e1a0613..60b60db6493 100644
--- a/compiler/rustc_symbol_mangling/src/legacy.rs
+++ b/compiler/rustc_symbol_mangling/src/legacy.rs
@@ -55,6 +55,26 @@ pub(super) fn mangle(
 
     let hash = get_symbol_hash(tcx, instance, instance_ty, instantiating_crate);
 
+    if let ty::InstanceDef::DropGlue(_drop_in_place, ty) = instance.def {
+        // Use `{{drop}}::<$TYPE>::$hash` as name for the drop glue instead of
+        // `core::mem::drop_in_place::$hash`.
+        let mut printer =
+            SymbolPrinter { tcx, path: SymbolPath::new(), keep_within_component: false };
+        printer.write_str("{{drop}}").unwrap();
+        printer.path.finalize_pending_component();
+        let printer = printer
+            .generic_delimiters(|mut printer| {
+                if let Some(ty) = ty {
+                    printer.print_type(ty)
+                } else {
+                    printer.write_str("_")?;
+                    Ok(printer)
+                }
+            })
+            .unwrap();
+        return printer.path.finish(hash);
+    }
+
     let mut printer = SymbolPrinter { tcx, path: SymbolPath::new(), keep_within_component: false }
         .print_def_path(def_id, &[])
         .unwrap();

From 4a48d680f2a27d3aff5507e973035681a2bec854 Mon Sep 17 00:00:00 2001
From: bjorn3 <bjorn3@users.noreply.github.com>
Date: Thu, 17 Dec 2020 09:57:48 +0100
Subject: [PATCH 2/2] Simplify based on eddyb's comment

---
 compiler/rustc_symbol_mangling/src/legacy.rs | 30 ++++++--------------
 1 file changed, 9 insertions(+), 21 deletions(-)

diff --git a/compiler/rustc_symbol_mangling/src/legacy.rs b/compiler/rustc_symbol_mangling/src/legacy.rs
index 60b60db6493..fd35915f644 100644
--- a/compiler/rustc_symbol_mangling/src/legacy.rs
+++ b/compiler/rustc_symbol_mangling/src/legacy.rs
@@ -55,28 +55,16 @@ pub(super) fn mangle(
 
     let hash = get_symbol_hash(tcx, instance, instance_ty, instantiating_crate);
 
-    if let ty::InstanceDef::DropGlue(_drop_in_place, ty) = instance.def {
-        // Use `{{drop}}::<$TYPE>::$hash` as name for the drop glue instead of
-        // `core::mem::drop_in_place::$hash`.
-        let mut printer =
-            SymbolPrinter { tcx, path: SymbolPath::new(), keep_within_component: false };
-        printer.write_str("{{drop}}").unwrap();
-        printer.path.finalize_pending_component();
-        let printer = printer
-            .generic_delimiters(|mut printer| {
-                if let Some(ty) = ty {
-                    printer.print_type(ty)
-                } else {
-                    printer.write_str("_")?;
-                    Ok(printer)
-                }
-            })
-            .unwrap();
-        return printer.path.finish(hash);
-    }
-
     let mut printer = SymbolPrinter { tcx, path: SymbolPath::new(), keep_within_component: false }
-        .print_def_path(def_id, &[])
+        .print_def_path(
+            def_id,
+            if let ty::InstanceDef::DropGlue(_, _) = instance.def {
+                // Add the name of the dropped type to the symbol name
+                &*instance.substs
+            } else {
+                &[]
+            },
+        )
         .unwrap();
 
     if let ty::InstanceDef::VtableShim(..) = instance.def {