Auto merge of #115794 - cjgillot:aggregate-no-box, r=davidtwco

Do not create a DerefLen place for `Box<[T]>`.

Fixes https://github.com/rust-lang/rust/issues/115789

10 files changed, 956 insertions, 1 deletions

diff --git a/compiler/rustc_mir_dataflow/src/value_analysis.rs b/compiler/rustc_mir_dataflow/src/value_analysis.rs
index dd20e5d7430..83766f31148 100644
--- a/compiler/rustc_mir_dataflow/src/value_analysis.rs
+++ b/compiler/rustc_mir_dataflow/src/value_analysis.rs
@@ -758,7 +758,9 @@ impl Map {
             self.value_count += 1;
         }
 
-        if let Some(ref_ty) = ty.builtin_deref(true) && let ty::Slice(..) = ref_ty.ty.kind() {
+        if let ty::Ref(_, ref_ty, _) | ty::RawPtr(ty::TypeAndMut { ty: ref_ty, .. }) = ty.kind()
+            && let ty::Slice(..) = ref_ty.kind()
+        {
             assert!(self.places[place].value_index.is_none(), "slices are not scalars");
 
             // Prepend new child to the linked list.
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.32bit.panic-abort.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.32bit.panic-abort.diff
new file mode 100644
index 00000000000..b9b46f16a8b
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.32bit.panic-abort.diff
@@ -0,0 +1,119 @@
+- // MIR for `main` before ConstProp
++ // MIR for `main` after ConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: A;
+      let mut _2: std::boxed::Box<[bool]>;
+      scope 1 {
+          debug a => _1;
+      }
+      scope 2 (inlined <Box<[bool]> as Default>::default) {
+          let _3: std::ptr::Unique<[bool]>;
+          let mut _4: std::ptr::Unique<[bool; 0]>;
+          scope 3 {
+              debug ptr => _3;
+          }
+          scope 4 (inlined Unique::<[bool; 0]>::dangling) {
+              let mut _5: std::ptr::NonNull<[bool; 0]>;
+              scope 5 (inlined NonNull::<[bool; 0]>::dangling) {
+                  let mut _7: usize;
+                  scope 6 {
+                      let _6: *mut [bool; 0];
+                      scope 7 {
+                          debug ptr => _6;
+                          scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
+                              debug ptr => _6;
+                              let mut _8: *const [bool; 0];
+                              scope 12 {
+                                  scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
+                                      debug ptr => _6;
+                                      scope 14 (inlined ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
+                                          debug self => _6;
+                                          let mut _9: *mut u8;
+                                          scope 15 {
+                                              scope 16 (inlined ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
+                                                  debug ptr => _9;
+                                                  scope 17 (inlined ptr::mut_ptr::<impl *mut u8>::addr) {
+                                                      debug self => _9;
+                                                      scope 18 {
+                                                          scope 19 (inlined ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
+                                                              debug self => _9;
+                                                          }
+                                                      }
+                                                  }
+                                              }
+                                          }
+                                      }
+                                  }
+                              }
+                          }
+                      }
+                      scope 8 (inlined align_of::<[bool; 0]>) {
+                      }
+                      scope 9 (inlined invalid_mut::<[bool; 0]>) {
+                          debug addr => _7;
+                          scope 10 {
+                          }
+                      }
+                  }
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          StorageLive(_5);
+          StorageLive(_6);
+          StorageLive(_7);
+-         _7 = AlignOf([bool; 0]);
+-         _6 = _7 as *mut [bool; 0] (Transmute);
++         _7 = const 1_usize;
++         _6 = const {0x1 as *mut [bool; 0]};
+          StorageDead(_7);
+          StorageLive(_8);
+          StorageLive(_9);
+-         _8 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
+-         _5 = NonNull::<[bool; 0]> { pointer: _8 };
++         _8 = const {0x1 as *const [bool; 0]};
++         _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};
+          StorageDead(_9);
+          StorageDead(_8);
+          StorageDead(_6);
+-         _4 = Unique::<[bool; 0]> { pointer: move _5, _marker: const PhantomData::<[bool; 0]> };
++         _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
+          StorageDead(_5);
+-         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize));
++         _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc7, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
+          StorageDead(_4);
+-         _2 = Box::<[bool]>(_3, const std::alloc::Global);
++         _2 = const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc10, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global);
+          StorageDead(_3);
+-         _1 = A { foo: move _2 };
++         _1 = A { foo: const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc11, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global) };
+          StorageDead(_2);
+          _0 = const ();
+          drop(_1) -> [return: bb1, unwind unreachable];
+      }
+  
+      bb1: {
+          StorageDead(_1);
+          return;
+      }
++ }
++ 
++ alloc11 (size: 8, align: 4) {
++     01 00 00 00 00 00 00 00                         │ ........
++ }
++ 
++ alloc10 (size: 8, align: 4) {
++     01 00 00 00 00 00 00 00                         │ ........
++ }
++ 
++ alloc7 (size: 8, align: 4) {
++     01 00 00 00 00 00 00 00                         │ ........
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.32bit.panic-unwind.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.32bit.panic-unwind.diff
new file mode 100644
index 00000000000..93b18f23e61
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.32bit.panic-unwind.diff
@@ -0,0 +1,123 @@
+- // MIR for `main` before ConstProp
++ // MIR for `main` after ConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: A;
+      let mut _2: std::boxed::Box<[bool]>;
+      scope 1 {
+          debug a => _1;
+      }
+      scope 2 (inlined <Box<[bool]> as Default>::default) {
+          let _3: std::ptr::Unique<[bool]>;
+          let mut _4: std::ptr::Unique<[bool; 0]>;
+          scope 3 {
+              debug ptr => _3;
+          }
+          scope 4 (inlined Unique::<[bool; 0]>::dangling) {
+              let mut _5: std::ptr::NonNull<[bool; 0]>;
+              scope 5 (inlined NonNull::<[bool; 0]>::dangling) {
+                  let mut _7: usize;
+                  scope 6 {
+                      let _6: *mut [bool; 0];
+                      scope 7 {
+                          debug ptr => _6;
+                          scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
+                              debug ptr => _6;
+                              let mut _8: *const [bool; 0];
+                              scope 12 {
+                                  scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
+                                      debug ptr => _6;
+                                      scope 14 (inlined ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
+                                          debug self => _6;
+                                          let mut _9: *mut u8;
+                                          scope 15 {
+                                              scope 16 (inlined ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
+                                                  debug ptr => _9;
+                                                  scope 17 (inlined ptr::mut_ptr::<impl *mut u8>::addr) {
+                                                      debug self => _9;
+                                                      scope 18 {
+                                                          scope 19 (inlined ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
+                                                              debug self => _9;
+                                                          }
+                                                      }
+                                                  }
+                                              }
+                                          }
+                                      }
+                                  }
+                              }
+                          }
+                      }
+                      scope 8 (inlined align_of::<[bool; 0]>) {
+                      }
+                      scope 9 (inlined invalid_mut::<[bool; 0]>) {
+                          debug addr => _7;
+                          scope 10 {
+                          }
+                      }
+                  }
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          StorageLive(_5);
+          StorageLive(_6);
+          StorageLive(_7);
+-         _7 = AlignOf([bool; 0]);
+-         _6 = _7 as *mut [bool; 0] (Transmute);
++         _7 = const 1_usize;
++         _6 = const {0x1 as *mut [bool; 0]};
+          StorageDead(_7);
+          StorageLive(_8);
+          StorageLive(_9);
+-         _8 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
+-         _5 = NonNull::<[bool; 0]> { pointer: _8 };
++         _8 = const {0x1 as *const [bool; 0]};
++         _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};
+          StorageDead(_9);
+          StorageDead(_8);
+          StorageDead(_6);
+-         _4 = Unique::<[bool; 0]> { pointer: move _5, _marker: const PhantomData::<[bool; 0]> };
++         _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
+          StorageDead(_5);
+-         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize));
++         _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc7, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
+          StorageDead(_4);
+-         _2 = Box::<[bool]>(_3, const std::alloc::Global);
++         _2 = const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc10, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global);
+          StorageDead(_3);
+-         _1 = A { foo: move _2 };
++         _1 = A { foo: const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc11, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global) };
+          StorageDead(_2);
+          _0 = const ();
+          drop(_1) -> [return: bb1, unwind: bb2];
+      }
+  
+      bb1: {
+          StorageDead(_1);
+          return;
+      }
+  
+      bb2 (cleanup): {
+          resume;
+      }
++ }
++ 
++ alloc11 (size: 8, align: 4) {
++     01 00 00 00 00 00 00 00                         │ ........
++ }
++ 
++ alloc10 (size: 8, align: 4) {
++     01 00 00 00 00 00 00 00                         │ ........
++ }
++ 
++ alloc7 (size: 8, align: 4) {
++     01 00 00 00 00 00 00 00                         │ ........
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.64bit.panic-abort.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.64bit.panic-abort.diff
new file mode 100644
index 00000000000..3d3af62856b
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.64bit.panic-abort.diff
@@ -0,0 +1,119 @@
+- // MIR for `main` before ConstProp
++ // MIR for `main` after ConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: A;
+      let mut _2: std::boxed::Box<[bool]>;
+      scope 1 {
+          debug a => _1;
+      }
+      scope 2 (inlined <Box<[bool]> as Default>::default) {
+          let _3: std::ptr::Unique<[bool]>;
+          let mut _4: std::ptr::Unique<[bool; 0]>;
+          scope 3 {
+              debug ptr => _3;
+          }
+          scope 4 (inlined Unique::<[bool; 0]>::dangling) {
+              let mut _5: std::ptr::NonNull<[bool; 0]>;
+              scope 5 (inlined NonNull::<[bool; 0]>::dangling) {
+                  let mut _7: usize;
+                  scope 6 {
+                      let _6: *mut [bool; 0];
+                      scope 7 {
+                          debug ptr => _6;
+                          scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
+                              debug ptr => _6;
+                              let mut _8: *const [bool; 0];
+                              scope 12 {
+                                  scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
+                                      debug ptr => _6;
+                                      scope 14 (inlined ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
+                                          debug self => _6;
+                                          let mut _9: *mut u8;
+                                          scope 15 {
+                                              scope 16 (inlined ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
+                                                  debug ptr => _9;
+                                                  scope 17 (inlined ptr::mut_ptr::<impl *mut u8>::addr) {
+                                                      debug self => _9;
+                                                      scope 18 {
+                                                          scope 19 (inlined ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
+                                                              debug self => _9;
+                                                          }
+                                                      }
+                                                  }
+                                              }
+                                          }
+                                      }
+                                  }
+                              }
+                          }
+                      }
+                      scope 8 (inlined align_of::<[bool; 0]>) {
+                      }
+                      scope 9 (inlined invalid_mut::<[bool; 0]>) {
+                          debug addr => _7;
+                          scope 10 {
+                          }
+                      }
+                  }
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          StorageLive(_5);
+          StorageLive(_6);
+          StorageLive(_7);
+-         _7 = AlignOf([bool; 0]);
+-         _6 = _7 as *mut [bool; 0] (Transmute);
++         _7 = const 1_usize;
++         _6 = const {0x1 as *mut [bool; 0]};
+          StorageDead(_7);
+          StorageLive(_8);
+          StorageLive(_9);
+-         _8 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
+-         _5 = NonNull::<[bool; 0]> { pointer: _8 };
++         _8 = const {0x1 as *const [bool; 0]};
++         _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};
+          StorageDead(_9);
+          StorageDead(_8);
+          StorageDead(_6);
+-         _4 = Unique::<[bool; 0]> { pointer: move _5, _marker: const PhantomData::<[bool; 0]> };
++         _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
+          StorageDead(_5);
+-         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize));
++         _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc7, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
+          StorageDead(_4);
+-         _2 = Box::<[bool]>(_3, const std::alloc::Global);
++         _2 = const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc10, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global);
+          StorageDead(_3);
+-         _1 = A { foo: move _2 };
++         _1 = A { foo: const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc11, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global) };
+          StorageDead(_2);
+          _0 = const ();
+          drop(_1) -> [return: bb1, unwind unreachable];
+      }
+  
+      bb1: {
+          StorageDead(_1);
+          return;
+      }
++ }
++ 
++ alloc11 (size: 16, align: 8) {
++     01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
++ }
++ 
++ alloc10 (size: 16, align: 8) {
++     01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
++ }
++ 
++ alloc7 (size: 16, align: 8) {
++     01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.64bit.panic-unwind.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.64bit.panic-unwind.diff
new file mode 100644
index 00000000000..1933f9bafb3
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.ConstProp.64bit.panic-unwind.diff
@@ -0,0 +1,123 @@
+- // MIR for `main` before ConstProp
++ // MIR for `main` after ConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: A;
+      let mut _2: std::boxed::Box<[bool]>;
+      scope 1 {
+          debug a => _1;
+      }
+      scope 2 (inlined <Box<[bool]> as Default>::default) {
+          let _3: std::ptr::Unique<[bool]>;
+          let mut _4: std::ptr::Unique<[bool; 0]>;
+          scope 3 {
+              debug ptr => _3;
+          }
+          scope 4 (inlined Unique::<[bool; 0]>::dangling) {
+              let mut _5: std::ptr::NonNull<[bool; 0]>;
+              scope 5 (inlined NonNull::<[bool; 0]>::dangling) {
+                  let mut _7: usize;
+                  scope 6 {
+                      let _6: *mut [bool; 0];
+                      scope 7 {
+                          debug ptr => _6;
+                          scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
+                              debug ptr => _6;
+                              let mut _8: *const [bool; 0];
+                              scope 12 {
+                                  scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
+                                      debug ptr => _6;
+                                      scope 14 (inlined ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
+                                          debug self => _6;
+                                          let mut _9: *mut u8;
+                                          scope 15 {
+                                              scope 16 (inlined ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
+                                                  debug ptr => _9;
+                                                  scope 17 (inlined ptr::mut_ptr::<impl *mut u8>::addr) {
+                                                      debug self => _9;
+                                                      scope 18 {
+                                                          scope 19 (inlined ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
+                                                              debug self => _9;
+                                                          }
+                                                      }
+                                                  }
+                                              }
+                                          }
+                                      }
+                                  }
+                              }
+                          }
+                      }
+                      scope 8 (inlined align_of::<[bool; 0]>) {
+                      }
+                      scope 9 (inlined invalid_mut::<[bool; 0]>) {
+                          debug addr => _7;
+                          scope 10 {
+                          }
+                      }
+                  }
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          StorageLive(_5);
+          StorageLive(_6);
+          StorageLive(_7);
+-         _7 = AlignOf([bool; 0]);
+-         _6 = _7 as *mut [bool; 0] (Transmute);
++         _7 = const 1_usize;
++         _6 = const {0x1 as *mut [bool; 0]};
+          StorageDead(_7);
+          StorageLive(_8);
+          StorageLive(_9);
+-         _8 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
+-         _5 = NonNull::<[bool; 0]> { pointer: _8 };
++         _8 = const {0x1 as *const [bool; 0]};
++         _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};
+          StorageDead(_9);
+          StorageDead(_8);
+          StorageDead(_6);
+-         _4 = Unique::<[bool; 0]> { pointer: move _5, _marker: const PhantomData::<[bool; 0]> };
++         _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
+          StorageDead(_5);
+-         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize));
++         _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc7, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
+          StorageDead(_4);
+-         _2 = Box::<[bool]>(_3, const std::alloc::Global);
++         _2 = const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc10, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global);
+          StorageDead(_3);
+-         _1 = A { foo: move _2 };
++         _1 = A { foo: const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc11, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global) };
+          StorageDead(_2);
+          _0 = const ();
+          drop(_1) -> [return: bb1, unwind: bb2];
+      }
+  
+      bb1: {
+          StorageDead(_1);
+          return;
+      }
+  
+      bb2 (cleanup): {
+          resume;
+      }
++ }
++ 
++ alloc11 (size: 16, align: 8) {
++     01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
++ }
++ 
++ alloc10 (size: 16, align: 8) {
++     01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
++ }
++ 
++ alloc7 (size: 16, align: 8) {
++     01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.32bit.panic-abort.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.32bit.panic-abort.diff
new file mode 100644
index 00000000000..7862c23da80
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.32bit.panic-abort.diff
@@ -0,0 +1,111 @@
+- // MIR for `main` before DataflowConstProp
++ // MIR for `main` after DataflowConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: A;
+      let mut _2: std::boxed::Box<[bool]>;
+      scope 1 {
+          debug a => _1;
+      }
+      scope 2 (inlined <Box<[bool]> as Default>::default) {
+          let _3: std::ptr::Unique<[bool]>;
+          let mut _4: std::ptr::Unique<[bool; 0]>;
+          scope 3 {
+              debug ptr => _3;
+          }
+          scope 4 (inlined Unique::<[bool; 0]>::dangling) {
+              let mut _5: std::ptr::NonNull<[bool; 0]>;
+              scope 5 (inlined NonNull::<[bool; 0]>::dangling) {
+                  let mut _7: usize;
+                  scope 6 {
+                      let _6: *mut [bool; 0];
+                      scope 7 {
+                          debug ptr => _6;
+                          scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
+                              debug ptr => _6;
+                              let mut _8: *const [bool; 0];
+                              scope 12 {
+                                  scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
+                                      debug ptr => _6;
+                                      scope 14 (inlined ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
+                                          debug self => _6;
+                                          let mut _9: *mut u8;
+                                          scope 15 {
+                                              scope 16 (inlined ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
+                                                  debug ptr => _9;
+                                                  scope 17 (inlined ptr::mut_ptr::<impl *mut u8>::addr) {
+                                                      debug self => _9;
+                                                      scope 18 {
+                                                          scope 19 (inlined ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
+                                                              debug self => _9;
+                                                          }
+                                                      }
+                                                  }
+                                              }
+                                          }
+                                      }
+                                  }
+                              }
+                          }
+                      }
+                      scope 8 (inlined align_of::<[bool; 0]>) {
+                      }
+                      scope 9 (inlined invalid_mut::<[bool; 0]>) {
+                          debug addr => _7;
+                          scope 10 {
+                          }
+                      }
+                  }
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          StorageLive(_5);
+          StorageLive(_6);
+          StorageLive(_7);
+          _7 = const 1_usize;
+          _6 = const {0x1 as *mut [bool; 0]};
+          StorageDead(_7);
+          StorageLive(_8);
+          StorageLive(_9);
+          _8 = const {0x1 as *const [bool; 0]};
+          _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};
+          StorageDead(_9);
+          StorageDead(_8);
+          StorageDead(_6);
+          _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
+          StorageDead(_5);
+          _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc7, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
+          StorageDead(_4);
+          _2 = const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc10, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global);
+          StorageDead(_3);
+          _1 = A { foo: const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc11, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global) };
+          StorageDead(_2);
+          _0 = const ();
+          drop(_1) -> [return: bb1, unwind unreachable];
+      }
+  
+      bb1: {
+          StorageDead(_1);
+          return;
+      }
+  }
+  
+  alloc11 (size: 8, align: 4) {
+      01 00 00 00 00 00 00 00                         │ ........
+  }
+  
+  alloc10 (size: 8, align: 4) {
+      01 00 00 00 00 00 00 00                         │ ........
+  }
+  
+  alloc7 (size: 8, align: 4) {
+      01 00 00 00 00 00 00 00                         │ ........
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.32bit.panic-unwind.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.32bit.panic-unwind.diff
new file mode 100644
index 00000000000..bd4150ebb45
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.32bit.panic-unwind.diff
@@ -0,0 +1,115 @@
+- // MIR for `main` before DataflowConstProp
++ // MIR for `main` after DataflowConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: A;
+      let mut _2: std::boxed::Box<[bool]>;
+      scope 1 {
+          debug a => _1;
+      }
+      scope 2 (inlined <Box<[bool]> as Default>::default) {
+          let _3: std::ptr::Unique<[bool]>;
+          let mut _4: std::ptr::Unique<[bool; 0]>;
+          scope 3 {
+              debug ptr => _3;
+          }
+          scope 4 (inlined Unique::<[bool; 0]>::dangling) {
+              let mut _5: std::ptr::NonNull<[bool; 0]>;
+              scope 5 (inlined NonNull::<[bool; 0]>::dangling) {
+                  let mut _7: usize;
+                  scope 6 {
+                      let _6: *mut [bool; 0];
+                      scope 7 {
+                          debug ptr => _6;
+                          scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
+                              debug ptr => _6;
+                              let mut _8: *const [bool; 0];
+                              scope 12 {
+                                  scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
+                                      debug ptr => _6;
+                                      scope 14 (inlined ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
+                                          debug self => _6;
+                                          let mut _9: *mut u8;
+                                          scope 15 {
+                                              scope 16 (inlined ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
+                                                  debug ptr => _9;
+                                                  scope 17 (inlined ptr::mut_ptr::<impl *mut u8>::addr) {
+                                                      debug self => _9;
+                                                      scope 18 {
+                                                          scope 19 (inlined ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
+                                                              debug self => _9;
+                                                          }
+                                                      }
+                                                  }
+                                              }
+                                          }
+                                      }
+                                  }
+                              }
+                          }
+                      }
+                      scope 8 (inlined align_of::<[bool; 0]>) {
+                      }
+                      scope 9 (inlined invalid_mut::<[bool; 0]>) {
+                          debug addr => _7;
+                          scope 10 {
+                          }
+                      }
+                  }
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          StorageLive(_5);
+          StorageLive(_6);
+          StorageLive(_7);
+          _7 = const 1_usize;
+          _6 = const {0x1 as *mut [bool; 0]};
+          StorageDead(_7);
+          StorageLive(_8);
+          StorageLive(_9);
+          _8 = const {0x1 as *const [bool; 0]};
+          _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};
+          StorageDead(_9);
+          StorageDead(_8);
+          StorageDead(_6);
+          _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
+          StorageDead(_5);
+          _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc7, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
+          StorageDead(_4);
+          _2 = const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc10, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global);
+          StorageDead(_3);
+          _1 = A { foo: const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc11, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global) };
+          StorageDead(_2);
+          _0 = const ();
+          drop(_1) -> [return: bb1, unwind: bb2];
+      }
+  
+      bb1: {
+          StorageDead(_1);
+          return;
+      }
+  
+      bb2 (cleanup): {
+          resume;
+      }
+  }
+  
+  alloc11 (size: 8, align: 4) {
+      01 00 00 00 00 00 00 00                         │ ........
+  }
+  
+  alloc10 (size: 8, align: 4) {
+      01 00 00 00 00 00 00 00                         │ ........
+  }
+  
+  alloc7 (size: 8, align: 4) {
+      01 00 00 00 00 00 00 00                         │ ........
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-abort.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-abort.diff
new file mode 100644
index 00000000000..312fc7b7a82
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-abort.diff
@@ -0,0 +1,111 @@
+- // MIR for `main` before DataflowConstProp
++ // MIR for `main` after DataflowConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: A;
+      let mut _2: std::boxed::Box<[bool]>;
+      scope 1 {
+          debug a => _1;
+      }
+      scope 2 (inlined <Box<[bool]> as Default>::default) {
+          let _3: std::ptr::Unique<[bool]>;
+          let mut _4: std::ptr::Unique<[bool; 0]>;
+          scope 3 {
+              debug ptr => _3;
+          }
+          scope 4 (inlined Unique::<[bool; 0]>::dangling) {
+              let mut _5: std::ptr::NonNull<[bool; 0]>;
+              scope 5 (inlined NonNull::<[bool; 0]>::dangling) {
+                  let mut _7: usize;
+                  scope 6 {
+                      let _6: *mut [bool; 0];
+                      scope 7 {
+                          debug ptr => _6;
+                          scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
+                              debug ptr => _6;
+                              let mut _8: *const [bool; 0];
+                              scope 12 {
+                                  scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
+                                      debug ptr => _6;
+                                      scope 14 (inlined ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
+                                          debug self => _6;
+                                          let mut _9: *mut u8;
+                                          scope 15 {
+                                              scope 16 (inlined ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
+                                                  debug ptr => _9;
+                                                  scope 17 (inlined ptr::mut_ptr::<impl *mut u8>::addr) {
+                                                      debug self => _9;
+                                                      scope 18 {
+                                                          scope 19 (inlined ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
+                                                              debug self => _9;
+                                                          }
+                                                      }
+                                                  }
+                                              }
+                                          }
+                                      }
+                                  }
+                              }
+                          }
+                      }
+                      scope 8 (inlined align_of::<[bool; 0]>) {
+                      }
+                      scope 9 (inlined invalid_mut::<[bool; 0]>) {
+                          debug addr => _7;
+                          scope 10 {
+                          }
+                      }
+                  }
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          StorageLive(_5);
+          StorageLive(_6);
+          StorageLive(_7);
+          _7 = const 1_usize;
+          _6 = const {0x1 as *mut [bool; 0]};
+          StorageDead(_7);
+          StorageLive(_8);
+          StorageLive(_9);
+          _8 = const {0x1 as *const [bool; 0]};
+          _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};
+          StorageDead(_9);
+          StorageDead(_8);
+          StorageDead(_6);
+          _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
+          StorageDead(_5);
+          _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc7, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
+          StorageDead(_4);
+          _2 = const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc10, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global);
+          StorageDead(_3);
+          _1 = A { foo: const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc11, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global) };
+          StorageDead(_2);
+          _0 = const ();
+          drop(_1) -> [return: bb1, unwind unreachable];
+      }
+  
+      bb1: {
+          StorageDead(_1);
+          return;
+      }
+  }
+  
+  alloc11 (size: 16, align: 8) {
+      01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
+  }
+  
+  alloc10 (size: 16, align: 8) {
+      01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
+  }
+  
+  alloc7 (size: 16, align: 8) {
+      01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-unwind.diff b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-unwind.diff
new file mode 100644
index 00000000000..3227d8b8435
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-unwind.diff
@@ -0,0 +1,115 @@
+- // MIR for `main` before DataflowConstProp
++ // MIR for `main` after DataflowConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: A;
+      let mut _2: std::boxed::Box<[bool]>;
+      scope 1 {
+          debug a => _1;
+      }
+      scope 2 (inlined <Box<[bool]> as Default>::default) {
+          let _3: std::ptr::Unique<[bool]>;
+          let mut _4: std::ptr::Unique<[bool; 0]>;
+          scope 3 {
+              debug ptr => _3;
+          }
+          scope 4 (inlined Unique::<[bool; 0]>::dangling) {
+              let mut _5: std::ptr::NonNull<[bool; 0]>;
+              scope 5 (inlined NonNull::<[bool; 0]>::dangling) {
+                  let mut _7: usize;
+                  scope 6 {
+                      let _6: *mut [bool; 0];
+                      scope 7 {
+                          debug ptr => _6;
+                          scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
+                              debug ptr => _6;
+                              let mut _8: *const [bool; 0];
+                              scope 12 {
+                                  scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
+                                      debug ptr => _6;
+                                      scope 14 (inlined ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
+                                          debug self => _6;
+                                          let mut _9: *mut u8;
+                                          scope 15 {
+                                              scope 16 (inlined ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
+                                                  debug ptr => _9;
+                                                  scope 17 (inlined ptr::mut_ptr::<impl *mut u8>::addr) {
+                                                      debug self => _9;
+                                                      scope 18 {
+                                                          scope 19 (inlined ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
+                                                              debug self => _9;
+                                                          }
+                                                      }
+                                                  }
+                                              }
+                                          }
+                                      }
+                                  }
+                              }
+                          }
+                      }
+                      scope 8 (inlined align_of::<[bool; 0]>) {
+                      }
+                      scope 9 (inlined invalid_mut::<[bool; 0]>) {
+                          debug addr => _7;
+                          scope 10 {
+                          }
+                      }
+                  }
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          StorageLive(_5);
+          StorageLive(_6);
+          StorageLive(_7);
+          _7 = const 1_usize;
+          _6 = const {0x1 as *mut [bool; 0]};
+          StorageDead(_7);
+          StorageLive(_8);
+          StorageLive(_9);
+          _8 = const {0x1 as *const [bool; 0]};
+          _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};
+          StorageDead(_9);
+          StorageDead(_8);
+          StorageDead(_6);
+          _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
+          StorageDead(_5);
+          _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc7, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
+          StorageDead(_4);
+          _2 = const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc10, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global);
+          StorageDead(_3);
+          _1 = A { foo: const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: alloc11, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global) };
+          StorageDead(_2);
+          _0 = const ();
+          drop(_1) -> [return: bb1, unwind: bb2];
+      }
+  
+      bb1: {
+          StorageDead(_1);
+          return;
+      }
+  
+      bb2 (cleanup): {
+          resume;
+      }
+  }
+  
+  alloc11 (size: 16, align: 8) {
+      01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
+  }
+  
+  alloc10 (size: 16, align: 8) {
+      01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
+  }
+  
+  alloc7 (size: 16, align: 8) {
+      01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/default_boxed_slice.rs b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.rs
new file mode 100644
index 00000000000..dfeccd3eb94
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/default_boxed_slice.rs
@@ -0,0 +1,17 @@
+// unit-test: DataflowConstProp
+// compile-flags: -Zmir-enable-passes=+ConstProp,+Inline
+// ignore-debug assertions change the output MIR
+// EMIT_MIR_FOR_EACH_BIT_WIDTH
+// EMIT_MIR_FOR_EACH_PANIC_STRATEGY
+
+struct A {
+    foo: Box<[bool]>,
+}
+
+// EMIT_MIR default_boxed_slice.main.ConstProp.diff
+// EMIT_MIR default_boxed_slice.main.DataflowConstProp.diff
+fn main() {
+    // ConstProp will create a constant of type `Box<[bool]>`.
+    // Verify that `DataflowConstProp` does not ICE trying to dereference it directly.
+    let a: A = A { foo: Box::default() };
+}