Adjust Alignment to emphasize that we don't look at its field

scottmcm · scottmcm · commit 9288c208a2ee · 2026-01-25T17:24:45.000-08:00
diff --git a/library/core/src/ptr/alignment.rs b/library/core/src/ptr/alignment.rs
@@ -13,7 +13,12 @@ use crate::{cmp, fmt, hash, mem, num};
 #[unstable(feature = "ptr_alignment_type", issue = "102070")]
 #[derive(Copy, Clone, PartialEq, Eq)]
 #[repr(transparent)]
-pub struct Alignment(AlignmentEnum);
+pub struct Alignment {
+    // This field is never used directly (nor is the enum),
+    // as it's just there to convey the validity invariant.
+    // (Hopefully it'll eventually be a pattern type instead.)
+    _inner_repr_trick: AlignmentEnum,
+}
 
 // Alignment is `repr(usize)`, but via extra steps.
 const _: () = assert!(size_of::<Alignment>() == size_of::<usize>());
@@ -37,7 +42,7 @@ impl Alignment {
     /// assert_eq!(Alignment::MIN.as_usize(), 1);
     /// ```
     #[unstable(feature = "ptr_alignment_type", issue = "102070")]
-    pub const MIN: Self = Self(AlignmentEnum::_Align1Shl0);
+    pub const MIN: Self = Self::new(1).unwrap();
 
     /// Returns the alignment for a type.
     ///
diff --git a/tests/mir-opt/dont_reset_cast_kind_without_updating_operand.test.GVN.32bit.panic-abort.diff b/tests/mir-opt/dont_reset_cast_kind_without_updating_operand.test.GVN.32bit.panic-abort.diff
@@ -111,7 +111,7 @@
   
       bb3: {
 -         _22 = handle_alloc_error(move _18) -> unwind unreachable;
-+         _22 = handle_alloc_error(const Layout {{ size: 0_usize, align: std::ptr::Alignment(std::ptr::alignment::AlignmentEnum::_Align1Shl0) }}) -> unwind unreachable;
++         _22 = handle_alloc_error(const Layout {{ size: 0_usize, align: std::ptr::Alignment {{ _inner_repr_trick: std::ptr::alignment::AlignmentEnum::_Align1Shl0 }} }}) -> unwind unreachable;
       }
   
       bb4: {
@@ -190,12 +190,12 @@
           StorageLive(_24);
 -         _24 = copy _17 as std::ptr::Alignment (Transmute);
 -         _18 = Layout { size: copy _16, align: move _24 };
-+         _24 = const std::ptr::Alignment(std::ptr::alignment::AlignmentEnum::_Align1Shl0);
-+         _18 = const Layout {{ size: 0_usize, align: std::ptr::Alignment(std::ptr::alignment::AlignmentEnum::_Align1Shl0) }};
++         _24 = const std::ptr::Alignment {{ _inner_repr_trick: std::ptr::alignment::AlignmentEnum::_Align1Shl0 }};
++         _18 = const Layout {{ size: 0_usize, align: std::ptr::Alignment {{ _inner_repr_trick: std::ptr::alignment::AlignmentEnum::_Align1Shl0 }} }};
           StorageDead(_24);
           StorageLive(_19);
 -         _19 = std::alloc::Global::alloc_impl_runtime(copy _18, const false) -> [return: bb7, unwind unreachable];
-+         _19 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: 0_usize, align: std::ptr::Alignment(std::ptr::alignment::AlignmentEnum::_Align1Shl0) }}, const false) -> [return: bb7, unwind unreachable];
++         _19 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: 0_usize, align: std::ptr::Alignment {{ _inner_repr_trick: std::ptr::alignment::AlignmentEnum::_Align1Shl0 }} }}, const false) -> [return: bb7, unwind unreachable];
       }
   
       bb7: {
diff --git a/tests/mir-opt/dont_reset_cast_kind_without_updating_operand.test.GVN.64bit.panic-abort.diff b/tests/mir-opt/dont_reset_cast_kind_without_updating_operand.test.GVN.64bit.panic-abort.diff
@@ -111,7 +111,7 @@
   
       bb3: {
 -         _22 = handle_alloc_error(move _18) -> unwind unreachable;
-+         _22 = handle_alloc_error(const Layout {{ size: 0_usize, align: std::ptr::Alignment(std::ptr::alignment::AlignmentEnum::_Align1Shl0) }}) -> unwind unreachable;
++         _22 = handle_alloc_error(const Layout {{ size: 0_usize, align: std::ptr::Alignment {{ _inner_repr_trick: std::ptr::alignment::AlignmentEnum::_Align1Shl0 }} }}) -> unwind unreachable;
       }
   
       bb4: {
@@ -190,12 +190,12 @@
           StorageLive(_24);
 -         _24 = copy _17 as std::ptr::Alignment (Transmute);
 -         _18 = Layout { size: copy _16, align: move _24 };
-+         _24 = const std::ptr::Alignment(std::ptr::alignment::AlignmentEnum::_Align1Shl0);
-+         _18 = const Layout {{ size: 0_usize, align: std::ptr::Alignment(std::ptr::alignment::AlignmentEnum::_Align1Shl0) }};
++         _24 = const std::ptr::Alignment {{ _inner_repr_trick: std::ptr::alignment::AlignmentEnum::_Align1Shl0 }};
++         _18 = const Layout {{ size: 0_usize, align: std::ptr::Alignment {{ _inner_repr_trick: std::ptr::alignment::AlignmentEnum::_Align1Shl0 }} }};
           StorageDead(_24);
           StorageLive(_19);
 -         _19 = std::alloc::Global::alloc_impl_runtime(copy _18, const false) -> [return: bb7, unwind unreachable];
-+         _19 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: 0_usize, align: std::ptr::Alignment(std::ptr::alignment::AlignmentEnum::_Align1Shl0) }}, const false) -> [return: bb7, unwind unreachable];
++         _19 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: 0_usize, align: std::ptr::Alignment {{ _inner_repr_trick: std::ptr::alignment::AlignmentEnum::_Align1Shl0 }} }}, const false) -> [return: bb7, unwind unreachable];
       }
   
       bb7: {
diff --git a/tests/mir-opt/gvn_ptr_eq_with_constant.main.GVN.diff b/tests/mir-opt/gvn_ptr_eq_with_constant.main.GVN.diff
@@ -42,7 +42,7 @@
           StorageLive(_3);
 -         _3 = const std::ptr::Alignment::of::<u8>::{constant#0};
 -         _2 = copy _3 as *mut u8 (Transmute);
-+         _3 = const std::ptr::Alignment(std::ptr::alignment::AlignmentEnum::_Align1Shl0);
++         _3 = const std::ptr::Alignment {{ _inner_repr_trick: std::ptr::alignment::AlignmentEnum::_Align1Shl0 }};
 +         _2 = const {0x1 as *mut u8};
           StorageDead(_3);
           StorageLive(_4);
diff --git a/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.32bit.panic-abort.diff b/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.32bit.panic-abort.diff
@@ -63,7 +63,7 @@
   
       bb3: {
 -         _1 = move ((_2 as Some).0: std::alloc::Layout);
-+         _1 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x00000000): std::ptr::alignment::AlignmentEnum) }};
++         _1 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x00000000): std::ptr::alignment::AlignmentEnum }} }};
           StorageDead(_8);
           StorageDead(_2);
           StorageLive(_3);
@@ -73,8 +73,8 @@
           StorageLive(_7);
 -         _7 = copy _1;
 -         _6 = std::alloc::Global::alloc_impl_runtime(move _7, const false) -> [return: bb4, unwind unreachable];
-+         _7 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x00000000): std::ptr::alignment::AlignmentEnum) }};
-+         _6 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x00000000): std::ptr::alignment::AlignmentEnum) }}, const false) -> [return: bb4, unwind unreachable];
++         _7 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x00000000): std::ptr::alignment::AlignmentEnum }} }};
++         _6 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x00000000): std::ptr::alignment::AlignmentEnum }} }}, const false) -> [return: bb4, unwind unreachable];
       }
   
       bb4: {
diff --git a/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.32bit.panic-unwind.diff b/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.32bit.panic-unwind.diff
@@ -64,7 +64,7 @@
   
       bb4: {
 -         _1 = move ((_2 as Some).0: std::alloc::Layout);
-+         _1 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x00000000): std::ptr::alignment::AlignmentEnum) }};
++         _1 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x00000000): std::ptr::alignment::AlignmentEnum }} }};
           StorageDead(_8);
           StorageDead(_2);
           StorageLive(_3);
@@ -74,8 +74,8 @@
           StorageLive(_7);
 -         _7 = copy _1;
 -         _6 = std::alloc::Global::alloc_impl_runtime(move _7, const false) -> [return: bb5, unwind continue];
-+         _7 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x00000000): std::ptr::alignment::AlignmentEnum) }};
-+         _6 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x00000000): std::ptr::alignment::AlignmentEnum) }}, const false) -> [return: bb5, unwind continue];
++         _7 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x00000000): std::ptr::alignment::AlignmentEnum }} }};
++         _6 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(4 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x00000000): std::ptr::alignment::AlignmentEnum }} }}, const false) -> [return: bb5, unwind continue];
       }
   
       bb5: {
diff --git a/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.64bit.panic-abort.diff b/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.64bit.panic-abort.diff
@@ -63,7 +63,7 @@
   
       bb3: {
 -         _1 = move ((_2 as Some).0: std::alloc::Layout);
-+         _1 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum) }};
++         _1 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum }} }};
           StorageDead(_8);
           StorageDead(_2);
           StorageLive(_3);
@@ -73,8 +73,8 @@
           StorageLive(_7);
 -         _7 = copy _1;
 -         _6 = std::alloc::Global::alloc_impl_runtime(move _7, const false) -> [return: bb4, unwind unreachable];
-+         _7 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum) }};
-+         _6 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum) }}, const false) -> [return: bb4, unwind unreachable];
++         _7 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum }} }};
++         _6 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum }} }}, const false) -> [return: bb4, unwind unreachable];
       }
   
       bb4: {
diff --git a/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.64bit.panic-unwind.diff b/tests/mir-opt/pre-codegen/issue_117368_print_invalid_constant.main.GVN.64bit.panic-unwind.diff
@@ -64,7 +64,7 @@
   
       bb4: {
 -         _1 = move ((_2 as Some).0: std::alloc::Layout);
-+         _1 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum) }};
++         _1 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum }} }};
           StorageDead(_8);
           StorageDead(_2);
           StorageLive(_3);
@@ -74,8 +74,8 @@
           StorageLive(_7);
 -         _7 = copy _1;
 -         _6 = std::alloc::Global::alloc_impl_runtime(move _7, const false) -> [return: bb5, unwind continue];
-+         _7 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum) }};
-+         _6 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment(Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum) }}, const false) -> [return: bb5, unwind continue];
++         _7 = const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum }} }};
++         _6 = std::alloc::Global::alloc_impl_runtime(const Layout {{ size: Indirect { alloc_id: ALLOC0, offset: Size(8 bytes) }: usize, align: std::ptr::Alignment {{ _inner_repr_trick: Scalar(0x0000000000000000): std::ptr::alignment::AlignmentEnum }} }}, const false) -> [return: bb5, unwind continue];
       }
   
       bb5: {
