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Add MaybeDangling #149614

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@WaffleLapkin WaffleLapkin commented Dec 3, 2025

cc #118166

@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Dec 3, 2025
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rust-log-analyzer commented Dec 3, 2025

The job x86_64-gnu-gcc failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot) 
test [mir-opt] tests/mir-opt/unusual_item_types.rs ... ok

failures:

---- [mir-opt] tests/mir-opt/pre-codegen/loops.rs stdout ----
3 fn vec_move(_1: Vec<impl Sized>) -> () {
4     debug v => _1;
5     let mut _0: ();
-     let mut _21: std::vec::IntoIter<impl Sized>;
7     let mut _22: std::vec::IntoIter<impl Sized>;
-     let mut _23: &mut std::vec::IntoIter<impl Sized>;
-     let mut _24: std::option::Option<impl Sized>;
-     let mut _25: isize;
-     let _27: ();
+     let mut _23: std::vec::IntoIter<impl Sized>;
+     let mut _24: &mut std::vec::IntoIter<impl Sized>;
+     let mut _25: std::option::Option<impl Sized>;
+     let mut _26: isize;
+     let _28: ();
12     scope 1 {
-         debug iter => _22;
-         let _26: impl Sized;
+         debug iter => _23;
+         let _27: impl Sized;
15         scope 2 {
-             debug x => _26;
+             debug x => _27;
17         }
18     }
19     scope 3 (inlined <Vec<impl Sized> as IntoIterator>::into_iter) {

20         debug self => _1;
-         let _2: std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
-         let mut _3: *const std::alloc::Global;
-         let mut _8: usize;
-         let mut _10: *mut impl Sized;
-         let mut _11: *const impl Sized;
-         let mut _12: usize;
-         let _28: &std::vec::Vec<impl Sized>;
-         let mut _29: &std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
-         let mut _30: &alloc::raw_vec::RawVec<impl Sized>;
-         let mut _31: &std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
-         let _32: &std::vec::Vec<impl Sized>;
-         let mut _33: &std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
-         let _34: &std::vec::Vec<impl Sized>;
-         let mut _35: &std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
-         let mut _36: &alloc::raw_vec::RawVec<impl Sized>;
-         let mut _37: &std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
+         let _3: std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
+         let mut _4: *const std::alloc::Global;
+         let mut _9: usize;
+         let mut _11: *mut impl Sized;
+         let mut _12: *const impl Sized;
+         let mut _13: usize;
+         let _29: &std::vec::Vec<impl Sized>;
+         let mut _30: &std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
+         let mut _31: &alloc::raw_vec::RawVec<impl Sized>;
+         let mut _32: &std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
+         let _33: &std::vec::Vec<impl Sized>;
+         let mut _34: &std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
+         let _35: &std::vec::Vec<impl Sized>;
+         let mut _36: &std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
+         let mut _37: &alloc::raw_vec::RawVec<impl Sized>;
+         let mut _38: &std::mem::ManuallyDrop<std::vec::Vec<impl Sized>>;
37         scope 4 {
-             debug me => _2;
+             debug me => _3;
39             scope 5 {
-                 debug alloc => const ManuallyDrop::<std::alloc::Global> {{ value: std::alloc::Global }};
-                 let _6: std::ptr::NonNull<impl Sized>;
+                 debug alloc => const ManuallyDrop::<std::alloc::Global> {{ value: MaybeDangling::<std::alloc::Global>(std::alloc::Global) }};
+                 let _7: std::ptr::NonNull<impl Sized>;
42                 scope 6 {
-                     debug buf => _6;
-                     let _7: *mut impl Sized;
+                     debug buf => _7;
+                     let _8: *mut impl Sized;
45                     scope 7 {
-                         debug begin => _7;
+                         debug begin => _8;
47                         scope 8 {
-                             debug end => _11;
-                             let _19: usize;
+                             debug end => _12;
+                             let _20: usize;
50                             scope 9 {
-                                 debug cap => _19;
+                                 debug cap => _20;
52                             }
-                             scope 39 (inlined <ManuallyDrop<Vec<impl Sized>> as Deref>::deref) {
-                                 debug self => _37;
+                             scope 45 (inlined <ManuallyDrop<Vec<impl Sized>> as Deref>::deref) {
+                                 debug self => _38;
+                                 scope 46 (inlined MaybeDangling::<Vec<impl Sized>>::as_ref) {
+                                 }
55                             }
-                             scope 40 (inlined alloc::raw_vec::RawVec::<impl Sized>::capacity) {
-                                 debug self => _36;
-                                 let mut _38: &alloc::raw_vec::RawVecInner;
-                                 scope 41 (inlined std::mem::size_of::<impl Sized>) {
+                             scope 47 (inlined alloc::raw_vec::RawVec::<impl Sized>::capacity) {
+                                 debug self => _37;
+                                 let mut _39: &alloc::raw_vec::RawVecInner;
+                                 scope 48 (inlined std::mem::size_of::<impl Sized>) {
60                                 }
-                                 scope 42 (inlined alloc::raw_vec::RawVecInner::capacity) {
-                                     debug self => _38;
+                                 scope 49 (inlined alloc::raw_vec::RawVecInner::capacity) {
+                                     debug self => _39;
63                                     debug elem_size => const <impl Sized as std::mem::SizedTypeProperties>::SIZE;
-                                     let mut _20: core::num::niche_types::UsizeNoHighBit;
-                                     scope 43 (inlined core::num::niche_types::UsizeNoHighBit::as_inner) {
-                                         debug self => _20;
+                                     let mut _21: core::num::niche_types::UsizeNoHighBit;
+                                     scope 50 (inlined core::num::niche_types::UsizeNoHighBit::as_inner) {
+                                         debug self => _21;
67                                     }
68                                 }
69                             }

70                         }
-                         scope 25 (inlined <ManuallyDrop<Vec<impl Sized>> as Deref>::deref) {
-                             debug self => _33;
+                         scope 29 (inlined <ManuallyDrop<Vec<impl Sized>> as Deref>::deref) {
+                             debug self => _34;
+                             scope 30 (inlined MaybeDangling::<Vec<impl Sized>>::as_ref) {
+                             }
73                         }
-                         scope 26 (inlined Vec::<impl Sized>::len) {
-                             debug self => _32;
-                             let mut _13: bool;
-                             scope 27 {
+                         scope 31 (inlined Vec::<impl Sized>::len) {
+                             debug self => _33;
+                             let mut _14: bool;
+                             scope 32 {
78                             }
79                         }
-                         scope 28 (inlined std::ptr::mut_ptr::<impl *mut impl Sized>::wrapping_byte_add) {
-                             debug self => _7;
-                             debug count => _12;
-                             let mut _14: *mut u8;
-                             let mut _18: *mut u8;
-                             scope 29 (inlined std::ptr::mut_ptr::<impl *mut impl Sized>::cast::<u8>) {
-                                 debug self => _7;
+                         scope 33 (inlined std::ptr::mut_ptr::<impl *mut impl Sized>::wrapping_byte_add) {
+                             debug self => _8;
+                             debug count => _13;
+                             let mut _15: *mut u8;
+                             let mut _19: *mut u8;
+                             scope 34 (inlined std::ptr::mut_ptr::<impl *mut impl Sized>::cast::<u8>) {
+                                 debug self => _8;
87                             }
-                             scope 30 (inlined std::ptr::mut_ptr::<impl *mut u8>::wrapping_add) {
-                                 debug self => _14;
-                                 debug count => _12;
-                                 let mut _15: isize;
---
96                                     let mut _17: *const u8;
+                                     let mut _18: *const u8;
97                                 }
98                             }
-                             scope 32 (inlined std::ptr::mut_ptr::<impl *mut u8>::with_metadata_of::<impl Sized>) {
-                                 debug self => _18;
-                                 debug meta => _5;
-                                 scope 33 (inlined std::ptr::metadata::<impl Sized>) {
-                                     debug ptr => _5;
+                             scope 37 (inlined std::ptr::mut_ptr::<impl *mut u8>::with_metadata_of::<impl Sized>) {
+                                 debug self => _19;
+                                 debug meta => _6;
+                                 scope 38 (inlined std::ptr::metadata::<impl Sized>) {
+                                     debug ptr => _6;
104                                 }
-                                 scope 34 (inlined std::ptr::from_raw_parts_mut::<impl Sized, ()>) {
+                                 scope 39 (inlined std::ptr::from_raw_parts_mut::<impl Sized, ()>) {
106                                 }
107                             }
108                         }

-                         scope 35 (inlined <ManuallyDrop<Vec<impl Sized>> as Deref>::deref) {
-                             debug self => _35;
+                         scope 40 (inlined <ManuallyDrop<Vec<impl Sized>> as Deref>::deref) {
+                             debug self => _36;
+                             scope 41 (inlined MaybeDangling::<Vec<impl Sized>>::as_ref) {
+                             }
111                         }
-                         scope 36 (inlined Vec::<impl Sized>::len) {
-                             debug self => _34;
-                             let mut _9: bool;
-                             scope 37 {
+                         scope 42 (inlined Vec::<impl Sized>::len) {
+                             debug self => _35;
+                             let mut _10: bool;
+                             scope 43 {
116                             }
117                         }
-                         scope 38 (inlined #[track_caller] std::ptr::mut_ptr::<impl *mut impl Sized>::add) {
-                             debug self => _7;
-                             debug count => _8;
+                         scope 44 (inlined #[track_caller] std::ptr::mut_ptr::<impl *mut impl Sized>::add) {
+                             debug self => _8;
+                             debug count => _9;
121                         }
122                     }
-                     scope 24 (inlined NonNull::<impl Sized>::as_ptr) {
-                         debug self => _6;
+                     scope 28 (inlined NonNull::<impl Sized>::as_ptr) {
+                         debug self => _7;
125                     }
126                 }
-                 scope 17 (inlined <ManuallyDrop<Vec<impl Sized>> as Deref>::deref) {
-                     debug self => _31;
+                 scope 20 (inlined <ManuallyDrop<Vec<impl Sized>> as Deref>::deref) {
+                     debug self => _32;
+                     scope 21 (inlined MaybeDangling::<Vec<impl Sized>>::as_ref) {
+                     }
129                 }
-                 scope 18 (inlined alloc::raw_vec::RawVec::<impl Sized>::non_null) {
-                     debug self => _30;
-                     scope 19 (inlined alloc::raw_vec::RawVecInner::non_null::<impl Sized>) {
-                         let mut _4: std::ptr::NonNull<u8>;
-                         scope 20 (inlined Unique::<u8>::cast::<impl Sized>) {
-                             scope 21 (inlined NonNull::<u8>::cast::<impl Sized>) {
-                                 let mut _5: *const impl Sized;
-                                 scope 22 (inlined NonNull::<u8>::as_ptr) {
+                 scope 22 (inlined alloc::raw_vec::RawVec::<impl Sized>::non_null) {
+                     debug self => _31;
+                     scope 23 (inlined alloc::raw_vec::RawVecInner::non_null::<impl Sized>) {
+                         let mut _5: std::ptr::NonNull<u8>;
+                         scope 24 (inlined Unique::<u8>::cast::<impl Sized>) {
+                             scope 25 (inlined NonNull::<u8>::cast::<impl Sized>) {
+                                 let mut _6: *const impl Sized;
+                                 scope 26 (inlined NonNull::<u8>::as_ptr) {
138                                 }
139                             }
140                         }
---
143                     }
144                 }

145             }
-             scope 11 (inlined <ManuallyDrop<Vec<impl Sized>> as Deref>::deref) {
-                 debug self => _29;
+             scope 12 (inlined <ManuallyDrop<Vec<impl Sized>> as Deref>::deref) {
+                 debug self => _30;
+                 scope 13 (inlined MaybeDangling::<Vec<impl Sized>>::as_ref) {
+                 }
148             }
-             scope 12 (inlined Vec::<impl Sized>::allocator) {
-                 debug self => _28;
-                 scope 13 (inlined alloc::raw_vec::RawVec::<impl Sized>::allocator) {
-                     scope 14 (inlined alloc::raw_vec::RawVecInner::allocator) {
+             scope 14 (inlined Vec::<impl Sized>::allocator) {
+                 debug self => _29;
+                 scope 15 (inlined alloc::raw_vec::RawVec::<impl Sized>::allocator) {
+                     scope 16 (inlined alloc::raw_vec::RawVecInner::allocator) {
153                     }
154                 }
155             }

-             scope 15 (inlined #[track_caller] std::ptr::read::<std::alloc::Global>) {
-                 debug src => _3;
+             scope 17 (inlined #[track_caller] std::ptr::read::<std::alloc::Global>) {
+                 debug src => _4;
158             }
-             scope 16 (inlined ManuallyDrop::<std::alloc::Global>::new) {
+             scope 18 (inlined ManuallyDrop::<std::alloc::Global>::new) {
160                 debug value => const std::alloc::Global;
+                 scope 19 (inlined MaybeDangling::<std::alloc::Global>::new) {
+                 }
161             }
162         }
163         scope 10 (inlined ManuallyDrop::<Vec<impl Sized>>::new) {

164             debug value => _1;
+             let mut _2: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>;
+             scope 11 (inlined MaybeDangling::<Vec<impl Sized>>::new) {
+             }
165         }
166     }
167 

---
174         StorageLive(_5);
-         StorageLive(_4);
-         StorageLive(_17);
-         StorageLive(_2);
-         _2 = ManuallyDrop::<Vec<impl Sized>> { value: copy _1 };
+         StorageLive(_18);
179         StorageLive(_3);
-         // DBG: _29 = &_2;
-         // DBG: _28 = &(_2.0: std::vec::Vec<impl Sized>);
-         _3 = &raw const ((((_2.0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>).0: alloc::raw_vec::RawVecInner).2: std::alloc::Global);
-         StorageDead(_3);
-         // DBG: _31 = &_2;
-         // DBG: _30 = &((_2.0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>);
-         _4 = copy (((((_2.0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>).0: alloc::raw_vec::RawVecInner).0: std::ptr::Unique<u8>).0: std::ptr::NonNull<u8>);
-         _5 = copy _4 as *const impl Sized (Transmute);
-         _6 = NonNull::<impl Sized> { pointer: copy _5 };
-         _7 = copy _4 as *mut impl Sized (Transmute);
+         StorageLive(_2);
+         _2 = MaybeDangling::<Vec<impl Sized>>(copy _1);
+         _3 = ManuallyDrop::<Vec<impl Sized>> { value: move _2 };
+         StorageDead(_2);
+         StorageLive(_4);
+         // DBG: _30 = &_3;
+         // DBG: _29 = &((_3.0: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>).0: std::vec::Vec<impl Sized>);
+         _4 = &raw const (((((_3.0: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>).0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>).0: alloc::raw_vec::RawVecInner).2: std::alloc::Global);
+         StorageDead(_4);
+         // DBG: _32 = &_3;
+         // DBG: _31 = &(((_3.0: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>).0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>);
+         _5 = copy ((((((_3.0: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>).0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>).0: alloc::raw_vec::RawVecInner).0: std::ptr::Unique<u8>).0: std::ptr::NonNull<u8>);
+         _6 = copy _5 as *const impl Sized (Transmute);
+         _7 = NonNull::<impl Sized> { pointer: copy _6 };
+         _8 = copy _5 as *mut impl Sized (Transmute);
190         switchInt(const <impl Sized as std::mem::SizedTypeProperties>::IS_ZST) -> [0: bb1, otherwise: bb2];
191     }
192 

193     bb1: {
-         StorageLive(_10);
-         StorageLive(_8);
-         // DBG: _35 = &_2;
-         // DBG: _34 = &(_2.0: std::vec::Vec<impl Sized>);
-         _8 = copy ((_2.0: std::vec::Vec<impl Sized>).1: usize);
+         StorageLive(_11);
199         StorageLive(_9);
-         _9 = Le(copy _8, const <impl Sized as std::mem::SizedTypeProperties>::MAX_SLICE_LEN);
-         assume(move _9);
-         StorageDead(_9);
-         _10 = Offset(copy _7, copy _8);
-         _11 = copy _10 as *const impl Sized (PtrToPtr);
-         StorageDead(_8);
+         // DBG: _36 = &_3;
+         // DBG: _35 = &((_3.0: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>).0: std::vec::Vec<impl Sized>);
+         _9 = copy (((_3.0: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>).0: std::vec::Vec<impl Sized>).1: usize);
+         StorageLive(_10);
+         _10 = Le(copy _9, const <impl Sized as std::mem::SizedTypeProperties>::MAX_SLICE_LEN);
+         assume(move _10);
206         StorageDead(_10);
+         _11 = Offset(copy _8, copy _9);
+         _12 = copy _11 as *const impl Sized (PtrToPtr);
+         StorageDead(_9);
+         StorageDead(_11);
207         goto -> bb4;
208     }
209 

210     bb2: {
-         StorageLive(_12);
-         // DBG: _33 = &_2;
-         // DBG: _32 = &(_2.0: std::vec::Vec<impl Sized>);
-         _12 = copy ((_2.0: std::vec::Vec<impl Sized>).1: usize);
215         StorageLive(_13);
-         _13 = Le(copy _12, const <impl Sized as std::mem::SizedTypeProperties>::MAX_SLICE_LEN);
-         assume(move _13);
-         StorageDead(_13);
-         StorageLive(_18);
+         // DBG: _34 = &_3;
+         // DBG: _33 = &((_3.0: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>).0: std::vec::Vec<impl Sized>);
+         _13 = copy (((_3.0: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>).0: std::vec::Vec<impl Sized>).1: usize);
220         StorageLive(_14);
-         _14 = copy _4 as *mut u8 (Transmute);
+         _14 = Le(copy _13, const <impl Sized as std::mem::SizedTypeProperties>::MAX_SLICE_LEN);
+         assume(move _14);
+         StorageDead(_14);
+         StorageLive(_19);
222         StorageLive(_15);
-         _15 = copy _12 as isize (IntToInt);
+         _15 = copy _5 as *mut u8 (Transmute);
224         StorageLive(_16);
-         _16 = copy _4 as *const u8 (Transmute);
-         _17 = arith_offset::<u8>(move _16, move _15) -> [return: bb3, unwind unreachable];
+         _16 = copy _13 as isize (IntToInt);
+         StorageLive(_17);
+         _17 = copy _5 as *const u8 (Transmute);
+         _18 = arith_offset::<u8>(move _17, move _16) -> [return: bb3, unwind unreachable];
227     }
228 
229     bb3: {

+         StorageDead(_17);
+         _19 = copy _18 as *mut u8 (PtrToPtr);
230         StorageDead(_16);
-         _18 = copy _17 as *mut u8 (PtrToPtr);
232         StorageDead(_15);
-         StorageDead(_14);
-         StorageDead(_18);
-         StorageDead(_12);
-         _11 = copy _17 as *const impl Sized (PtrToPtr);
---
238     }
239 

240     bb4: {
-         // DBG: _37 = &_2;
-         // DBG: _36 = &((_2.0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>);
-         // DBG: _38 = &(((_2.0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>).0: alloc::raw_vec::RawVecInner);
+         // DBG: _38 = &_3;
+         // DBG: _37 = &(((_3.0: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>).0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>);
+         // DBG: _39 = &((((_3.0: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>).0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>).0: alloc::raw_vec::RawVecInner);
244         switchInt(const <impl Sized as std::mem::SizedTypeProperties>::SIZE) -> [0: bb5, otherwise: bb6];
245     }
246 

247     bb5: {
-         _19 = const usize::MAX;
+         _20 = const usize::MAX;
249         goto -> bb7;
250     }
251 

252     bb6: {
-         StorageLive(_20);
-         _20 = copy ((((_2.0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>).0: alloc::raw_vec::RawVecInner).1: core::num::niche_types::UsizeNoHighBit);
-         _19 = copy _20 as usize (Transmute);
-         StorageDead(_20);
+         StorageLive(_21);
+         _21 = copy (((((_3.0: std::mem::MaybeDangling<std::vec::Vec<impl Sized>>).0: std::vec::Vec<impl Sized>).0: alloc::raw_vec::RawVec<impl Sized>).0: alloc::raw_vec::RawVecInner).1: core::num::niche_types::UsizeNoHighBit);
+         _20 = copy _21 as usize (Transmute);
+         StorageDead(_21);
257         goto -> bb7;
258     }
259 

260     bb7: {
-         _21 = std::vec::IntoIter::<impl Sized> { buf: copy _6, phantom: const ZeroSized: PhantomData<impl Sized>, cap: move _19, alloc: const ManuallyDrop::<std::alloc::Global> {{ value: std::alloc::Global }}, ptr: copy _6, end: copy _11 };
-         StorageDead(_2);
-         StorageDead(_17);
-         StorageDead(_4);
+         _22 = std::vec::IntoIter::<impl Sized> { buf: copy _7, phantom: const ZeroSized: PhantomData<impl Sized>, cap: move _20, alloc: const ManuallyDrop::<std::alloc::Global> {{ value: MaybeDangling::<std::alloc::Global>(std::alloc::Global) }}, ptr: copy _7, end: copy _12 };
+         StorageDead(_3);
+         StorageDead(_18);
265         StorageDead(_5);
-         StorageDead(_19);
-         StorageDead(_11);
---
274 

275     bb8: {
-         StorageLive(_24);
-         _23 = &mut _22;
-         _24 = <std::vec::IntoIter<impl Sized> as Iterator>::next(move _23) -> [return: bb9, unwind: bb15];
+         StorageLive(_25);
+         _24 = &mut _23;
+         _25 = <std::vec::IntoIter<impl Sized> as Iterator>::next(move _24) -> [return: bb9, unwind: bb15];
279     }
280 
281     bb9: {

-         _25 = discriminant(_24);
-         switchInt(move _25) -> [0: bb10, 1: bb12, otherwise: bb14];
+         _26 = discriminant(_25);
+         switchInt(move _26) -> [0: bb10, 1: bb12, otherwise: bb14];
284     }
285 
286     bb10: {

-         StorageDead(_24);
-         drop(_22) -> [return: bb11, unwind continue];
+         StorageDead(_25);
+         drop(_23) -> [return: bb11, unwind continue];
289     }
290 
291     bb11: {

+         StorageDead(_23);
292         StorageDead(_22);
-         StorageDead(_21);
294         return;
295     }
296 

297     bb12: {
-         _26 = move ((_24 as Some).0: impl Sized);
-         _27 = opaque::<impl Sized>(move _26) -> [return: bb13, unwind: bb15];
+         _27 = move ((_25 as Some).0: impl Sized);
+         _28 = opaque::<impl Sized>(move _27) -> [return: bb13, unwind: bb15];
300     }
301 
302     bb13: {

-         StorageDead(_24);
+         StorageDead(_25);
304         goto -> bb8;
305     }
306 

309     }
310 
311     bb15 (cleanup): {
-         drop(_22) -> [return: bb16, unwind terminate(cleanup)];
+         drop(_23) -> [return: bb16, unwind terminate(cleanup)];
313     }
314 
315     bb16 (cleanup): {


thread '[mir-opt] tests/mir-opt/pre-codegen/loops.rs' panicked at src/tools/compiletest/src/runtest/mir_opt.rs:84:21:
Actual MIR output differs from expected MIR output /checkout/tests/mir-opt/pre-codegen/loops.vec_move.PreCodegen.after.mir
stack backtrace:
   5: __rustc::rust_begin_unwind
             at /rustc/3b4dd9bf1410f8da6329baa36ce5e37673cbbd1f/library/std/src/panicking.rs:698:5
   6: core::panicking::panic_fmt
             at /rustc/3b4dd9bf1410f8da6329baa36ce5e37673cbbd1f/library/core/src/panicking.rs:80:14

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theemathas
theemathas reviewed Dec 4, 2025
View reviewed changes
library/core/src/mem/manually_drop.rs
Comment on lines +187 to 192
#[stable(feature = "manually_drop", since = "1.20.0")]
impl<T: ?Sized + PartialEq> PartialEq for ManuallyDrop<T> {
fn eq(&self, other: &Self) -> bool {
self.value.as_ref().eq(other.value.as_ref())
}
}
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@theemathas theemathas Dec 4, 2025

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You also need to implement StructuralPartialEq, since ManuallyDrop in a const can currently be used in patterns on stable.

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