Implement wide not-null pointer patterns

Author: oli-obk

compiler/rustc_middle/src/ty/layout.rs

@@ -822,11 +822,21 @@ where
                 | ty::FnDef(..)
                 | ty::CoroutineWitness(..)
                 | ty::Foreign(..)
-                | ty::Pat(_, _)
                 | ty::Dynamic(_, _, ty::Dyn) => {
                     bug!("TyAndLayout::field({:?}): not applicable", this)
                 }
 
+                // May contain wide pointers
+                ty::Pat(base, pat) => match *pat {
+                    ty::PatternKind::NotNull => {
+                        assert_eq!(i, 0);
+                        TyMaybeWithLayout::Ty(base)
+                    }
+                    ty::PatternKind::Range { .. } | ty::PatternKind::Or(_) => {
+                        bug!("TyAndLayout::field({this:?}): only applicable to !null patterns")
+                    }
+                },
+
                 ty::UnsafeBinder(bound_ty) => {
                     let ty = tcx.instantiate_bound_regions_with_erased(bound_ty.into());
                     field_ty_or_layout(TyAndLayout { ty, ..this }, cx, i)

compiler/rustc_ty_utils/src/layout.rs

@@ -273,6 +273,12 @@ fn layout_of_uncached<'tcx>(
                         };
 
                         layout.largest_niche = Some(niche);
+                        // Make wide pointer pattern types contain only a single field
+                        // of the wide pointer type itself.
+                        layout.fields = FieldsShape::Arbitrary {
+                            offsets: [Size::ZERO].into_iter().collect(),
+                            memory_index: [0].into_iter().collect(),
+                        }
                     } else {
                         bug!(
                             "pattern type with `!null` pattern but not scalar/pair layout: {ty:?}, {layout:?}"

tests/ui/type/pattern_types/non_null.rs

@@ -15,6 +15,9 @@ type NonNull<T> = pattern_type!(*const T is !null); //~ ERROR layout_of
 #[rustc_layout(debug)]
 type Test = Option<NonNull<()>>; //~ ERROR layout_of
 
+#[rustc_layout(debug)]
+type Wide = pattern_type!(*const [u8] is !null); //~ ERROR layout_of
+
 const _: () = assert!(size_of::<NonNull<()>>() == size_of::<Option<NonNull<()>>>());
 
 fn main() {}

tests/ui/type/pattern_types/non_null.stderr

@@ -13,7 +13,14 @@ error: layout_of((*const T) is !null) = Layout {
                    valid_range: 1..=$MAX,
                },
            ),
-           fields: Primitive,
+           fields: Arbitrary {
+               offsets: [
+                   Size(0 bytes),
+               ],
+               memory_index: [
+                   0,
+               ],
+           },
            largest_niche: Some(
                Niche {
                    offset: Size(0 bytes),
@@ -153,5 +160,59 @@ error: layout_of(Option<(*const ()) is !null>) = Layout {
 LL | type Test = Option<NonNull<()>>;
    | ^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: layout_of((*const [u8]) is !null) = Layout {
+           size: Size($N bytes),
+           align: AbiAlign {
+               abi: Align($N bytes),
+           },
+           backend_repr: ScalarPair(
+               Initialized {
+                   value: Pointer(
+                       AddressSpace(
+                           0,
+                       ),
+                   ),
+                   valid_range: 1..=$MAX,
+               },
+               Initialized {
+                   value: Int(
+                       I64,
+                       false,
+                   ),
+                   valid_range: 0..=$MAX,
+               },
+           ),
+           fields: Arbitrary {
+               offsets: [
+                   Size(0 bytes),
+               ],
+               memory_index: [
+                   0,
+               ],
+           },
+           largest_niche: Some(
+               Niche {
+                   offset: Size(0 bytes),
+                   value: Pointer(
+                       AddressSpace(
+                           0,
+                       ),
+                   ),
+                   valid_range: 1..=$MAX,
+               },
+           ),
+           uninhabited: false,
+           variants: Single {
+               index: 0,
+           },
+           max_repr_align: None,
+           unadjusted_abi_align: Align($N bytes),
+           randomization_seed: $SEED,
+       }
+  --> $DIR/non_null.rs:19:1
+   |
+LL | type Wide = pattern_type!(*const [u8] is !null);
+   | ^^^^^^^^^
+
+error: aborting due to 3 previous errors