From 6e32a165208242153af66a12cbe4448b05525f82 Mon Sep 17 00:00:00 2001
From: DrMeepster <19316085+DrMeepster@users.noreply.github.com>
Date: Sun, 26 Jun 2022 13:58:37 -0700
Subject: [PATCH 1/4] fix box with custom allocator in miri

---
 compiler/rustc_const_eval/src/interpret/cast.rs  | 16 ----------------
 .../rustc_const_eval/src/interpret/validity.rs   |  5 ++++-
 2 files changed, 4 insertions(+), 17 deletions(-)

diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
index fb484fba9fd06..076415b2d1b2f 100644
--- a/compiler/rustc_const_eval/src/interpret/cast.rs
+++ b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -366,22 +366,6 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             }
             (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => {
                 assert_eq!(def_a, def_b);
-                if def_a.is_box() || def_b.is_box() {
-                    if !def_a.is_box() || !def_b.is_box() {
-                        span_bug!(
-                            self.cur_span(),
-                            "invalid unsizing between {:?} -> {:?}",
-                            src.layout.ty,
-                            cast_ty.ty
-                        );
-                    }
-                    return self.unsize_into_ptr(
-                        src,
-                        dest,
-                        src.layout.ty.boxed_ty(),
-                        cast_ty.ty.boxed_ty(),
-                    );
-                }
 
                 // unsizing of generic struct with pointer fields
                 // Example: `Arc<T>` -> `Arc<Trait>`
diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index 630281bb09254..3809030b51560 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -594,7 +594,10 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 Ok(true)
             }
             ty::Adt(def, ..) if def.is_box() => {
-                self.check_safe_pointer(value, "box")?;
+                let unique = self.ecx.operand_field(value, 0)?;
+                let nonnull = self.ecx.operand_field(&unique, 0)?;
+                let ptr = self.ecx.operand_field(&nonnull, 0)?;
+                self.check_safe_pointer(&ptr, "box")?;
                 Ok(true)
             }
             ty::FnPtr(_sig) => {

From d317988505cade110cc8c9f1d03e6a98622f10bd Mon Sep 17 00:00:00 2001
From: DrMeepster <19316085+DrMeepster@users.noreply.github.com>
Date: Sun, 26 Jun 2022 18:54:03 -0700
Subject: [PATCH 2/4] validate box's allocator

---
 compiler/rustc_const_eval/src/interpret/validity.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index 3809030b51560..00e4472721f3f 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -598,6 +598,9 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 let nonnull = self.ecx.operand_field(&unique, 0)?;
                 let ptr = self.ecx.operand_field(&nonnull, 0)?;
                 self.check_safe_pointer(&ptr, "box")?;
+
+                let allocator = self.ecx.operand_field(value, 1)?;
+                self.visit_field(value, 1, &allocator)?;
                 Ok(true)
             }
             ty::FnPtr(_sig) => {

From 9f9c31171888150912487d97dba19c6586007310 Mon Sep 17 00:00:00 2001
From: DrMeepster <19316085+DrMeepster@users.noreply.github.com>
Date: Tue, 28 Jun 2022 02:19:52 -0700
Subject: [PATCH 3/4] Validate all fields of box instead of validating
 allocator specifically

---
 compiler/rustc_const_eval/src/interpret/validity.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index 00e4472721f3f..702954884a08b 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -599,8 +599,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 let ptr = self.ecx.operand_field(&nonnull, 0)?;
                 self.check_safe_pointer(&ptr, "box")?;
 
-                let allocator = self.ecx.operand_field(value, 1)?;
-                self.visit_field(value, 1, &allocator)?;
+                // Check other fields of Box
+                self.walk_value(op)?;
                 Ok(true)
             }
             ty::FnPtr(_sig) => {

From 9039265c308fccf6599080db51e6db103ecaf5ad Mon Sep 17 00:00:00 2001
From: DrMeepster <19316085+DrMeepster@users.noreply.github.com>
Date: Tue, 28 Jun 2022 13:48:13 -0700
Subject: [PATCH 4/4] fix silly mistake

you should always run x.py check before pushing
---
 compiler/rustc_const_eval/src/interpret/validity.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index 702954884a08b..905ab6cb578fc 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -600,7 +600,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 self.check_safe_pointer(&ptr, "box")?;
 
                 // Check other fields of Box
-                self.walk_value(op)?;
+                self.walk_value(value)?;
                 Ok(true)
             }
             ty::FnPtr(_sig) => {