From 9f44caa8579d69e829d89ffaae0260c85141fdfc Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Fri, 10 Jan 2025 04:36:11 +0000
Subject: [PATCH 1/2] Do not treat vtable supertraits as distinct when bound
 with different bound vars

---
 src/constant.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/constant.rs b/src/constant.rs
index 3e7b81a96b68..05ba53430a8a 100644
--- a/src/constant.rs
+++ b/src/constant.rs
@@ -245,7 +245,10 @@ pub(crate) fn data_id_for_vtable<'tcx>(
     ty: Ty<'tcx>,
     trait_ref: Option<Binder<'tcx, ExistentialTraitRef<'tcx>>>,
 ) -> DataId {
-    let alloc_id = tcx.vtable_allocation((ty, trait_ref));
+    let alloc_id = tcx.vtable_allocation((
+        ty,
+        trait_ref.map(|principal| tcx.instantiate_bound_regions_with_erased(principal)),
+    ));
     data_id_for_alloc_id(cx, module, alloc_id, Mutability::Not)
 }
 

From 96bea7ac909c021538358f66ed9ef77895a1883f Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Fri, 10 Jan 2025 20:26:10 +0000
Subject: [PATCH 2/2] Use ExistentialTraitRef throughout codegen

---
 src/constant.rs | 25 +++++++++++++++----------
 src/unsize.rs   |  7 ++++++-
 src/vtable.rs   |  2 +-
 3 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/src/constant.rs b/src/constant.rs
index 05ba53430a8a..425b2adf32a3 100644
--- a/src/constant.rs
+++ b/src/constant.rs
@@ -6,7 +6,7 @@ use cranelift_module::*;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::interpret::{AllocId, GlobalAlloc, Scalar, read_target_uint};
-use rustc_middle::ty::{Binder, ExistentialTraitRef, ScalarInt};
+use rustc_middle::ty::{ExistentialTraitRef, ScalarInt};
 
 use crate::prelude::*;
 
@@ -167,7 +167,9 @@ pub(crate) fn codegen_const_value<'tcx>(
                             &mut fx.constants_cx,
                             fx.module,
                             ty,
-                            dyn_ty.principal(),
+                            dyn_ty.principal().map(|principal| {
+                                fx.tcx.instantiate_bound_regions_with_erased(principal)
+                            }),
                         );
                         let local_data_id =
                             fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
@@ -243,12 +245,9 @@ pub(crate) fn data_id_for_vtable<'tcx>(
     cx: &mut ConstantCx,
     module: &mut dyn Module,
     ty: Ty<'tcx>,
-    trait_ref: Option<Binder<'tcx, ExistentialTraitRef<'tcx>>>,
+    trait_ref: Option<ExistentialTraitRef<'tcx>>,
 ) -> DataId {
-    let alloc_id = tcx.vtable_allocation((
-        ty,
-        trait_ref.map(|principal| tcx.instantiate_bound_regions_with_erased(principal)),
-    ));
+    let alloc_id = tcx.vtable_allocation((ty, trait_ref));
     data_id_for_alloc_id(cx, module, alloc_id, Mutability::Not)
 }
 
@@ -463,9 +462,15 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
                 GlobalAlloc::Memory(target_alloc) => {
                     data_id_for_alloc_id(cx, module, alloc_id, target_alloc.inner().mutability)
                 }
-                GlobalAlloc::VTable(ty, dyn_ty) => {
-                    data_id_for_vtable(tcx, cx, module, ty, dyn_ty.principal())
-                }
+                GlobalAlloc::VTable(ty, dyn_ty) => data_id_for_vtable(
+                    tcx,
+                    cx,
+                    module,
+                    ty,
+                    dyn_ty
+                        .principal()
+                        .map(|principal| tcx.instantiate_bound_regions_with_erased(principal)),
+                ),
                 GlobalAlloc::Static(def_id) => {
                     if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
                     {
diff --git a/src/unsize.rs b/src/unsize.rs
index 2843e5bbdfb2..f8bbb2149201 100644
--- a/src/unsize.rs
+++ b/src/unsize.rs
@@ -61,7 +61,12 @@ pub(crate) fn unsized_info<'tcx>(
                 old_info
             }
         }
-        (_, ty::Dynamic(data, ..)) => crate::vtable::get_vtable(fx, source, data.principal()),
+        (_, ty::Dynamic(data, ..)) => crate::vtable::get_vtable(
+            fx,
+            source,
+            data.principal()
+                .map(|principal| fx.tcx.instantiate_bound_regions_with_erased(principal)),
+        ),
         _ => bug!("unsized_info: invalid unsizing {:?} -> {:?}", source, target),
     }
 }
diff --git a/src/vtable.rs b/src/vtable.rs
index 82b6178be9dc..a460023b59cb 100644
--- a/src/vtable.rs
+++ b/src/vtable.rs
@@ -90,7 +90,7 @@ pub(crate) fn get_ptr_and_method_ref<'tcx>(
 pub(crate) fn get_vtable<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     ty: Ty<'tcx>,
-    trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+    trait_ref: Option<ty::ExistentialTraitRef<'tcx>>,
 ) -> Value {
     let data_id = data_id_for_vtable(fx.tcx, &mut fx.constants_cx, fx.module, ty, trait_ref);
     let local_data_id = fx.module.declare_data_in_func(data_id, fx.bcx.func);