Backport new sized-hierarchy trait bounds in old ways

Author: ShoyuVanilla

crates/hir-def/src/lang_item.rs

@@ -308,6 +308,8 @@ impl LangItem {
 language_item_table! {
 //  Variant name,            Name,                     Getter method name,         Target                  Generic requirements;
     Sized,                   sym::sized,               sized_trait,                Target::Trait,          GenericRequirement::Exact(0);
+    MetaSized,               sym::meta_sized,          sized_trait,                Target::Trait,          GenericRequirement::Exact(0);
+    PointeeSized,            sym::pointee_sized,       sized_trait,                Target::Trait,          GenericRequirement::Exact(0);
     Unsize,                  sym::unsize,              unsize_trait,               Target::Trait,          GenericRequirement::Minimum(1);
     /// Trait injected by `#[derive(PartialEq)]`, (i.e. "Partial EQ").
     StructuralPeq,           sym::structural_peq,      structural_peq_trait,       Target::Trait,          GenericRequirement::None;

crates/hir-ty/src/lower.rs

@@ -581,11 +581,28 @@ impl<'a> TyLoweringContext<'a> {
         match bound {
             &TypeBound::Path(path, TraitBoundModifier::None) | &TypeBound::ForLifetime(_, path) => {
                 // FIXME Don't silently drop the hrtb lifetimes here
-                if let Some((trait_ref, ctx)) = self.lower_trait_ref_from_path(path, self_ty) {
-                    if !ignore_bindings {
-                        assoc_bounds = ctx.assoc_type_bindings_from_type_bound(trait_ref.clone());
+                if let Some((trait_ref, mut ctx)) =
+                    self.lower_trait_ref_from_path(path, self_ty.clone())
+                {
+                    // FIXME(sized-hierarchy): Remove this bound modifications once we have implemented
+                    // sized-hierarchy correctly.
+                    let meta_sized = LangItem::MetaSized
+                        .resolve_trait(ctx.ty_ctx().db, ctx.ty_ctx().resolver.krate());
+                    let pointee_sized = LangItem::PointeeSized
+                        .resolve_trait(ctx.ty_ctx().db, ctx.ty_ctx().resolver.krate());
+                    if meta_sized.is_some_and(|it| it == trait_ref.hir_trait_id()) {
+                        // Ignore this bound
+                    } else if pointee_sized.is_some_and(|it| it == trait_ref.hir_trait_id()) {
+                        // Regard this as `?Sized` bound
+                        ctx.ty_ctx().unsized_types.insert(self_ty);
+                    } else {
+                        if !ignore_bindings {
+                            assoc_bounds =
+                                ctx.assoc_type_bindings_from_type_bound(trait_ref.clone());
+                        }
+                        clause =
+                            Some(crate::wrap_empty_binders(WhereClause::Implemented(trait_ref)));
                     }
-                    clause = Some(crate::wrap_empty_binders(WhereClause::Implemented(trait_ref)));
                 }
             }
             &TypeBound::Path(path, TraitBoundModifier::Maybe) => {
@@ -945,8 +962,32 @@ pub(crate) fn generic_predicates_for_param_query(
         | WherePredicate::TypeBound { target, bound, .. } => {
             let invalid_target = { ctx.lower_ty_only_param(*target) != Some(param_id) };
             if invalid_target {
-                // If this is filtered out without lowering, `?Sized` is not gathered into `ctx.unsized_types`
-                if let TypeBound::Path(_, TraitBoundModifier::Maybe) = bound {
+                // FIXME(sized-hierarchy): Revisit and adjust this properly once we have implemented
+                // sized-hierarchy correctly.
+                // If this is filtered out without lowering, `?Sized` or `PointeeSized` is not gathered into
+                // `ctx.unsized_types`
+                let lower = || -> bool {
+                    match bound {
+                        TypeBound::Path(_, TraitBoundModifier::Maybe) => true,
+                        TypeBound::Path(path, _) | TypeBound::ForLifetime(_, path) => {
+                            let TypeRef::Path(path) = &ctx.store[path.type_ref()] else {
+                                return false;
+                            };
+                            let Some(pointee_sized) =
+                                LangItem::PointeeSized.resolve_trait(ctx.db, ctx.resolver.krate())
+                            else {
+                                return false;
+                            };
+                            // Lower the path directly with `Resolver` instead of PathLoweringContext`
+                            // to prevent diagnostics duplications.
+                            ctx.resolver.resolve_path_in_type_ns_fully(ctx.db, path).is_some_and(
+                                |it| matches!(it, TypeNs::TraitId(tr) if tr == pointee_sized),
+                            )
+                        }
+                        _ => false,
+                    }
+                }();
+                if lower {
                     ctx.lower_where_predicate(pred, true).for_each(drop);
                 }
                 return false;

crates/ide/src/inlay_hints/bounds.rs

@@ -143,7 +143,7 @@ fn foo<T>() {}
                                             file_id: FileId(
                                                 1,
                                             ),
-                                            range: 135..140,
+                                            range: 446..451,
                                         },
                                     ),
                                 ),

crates/intern/src/symbol/symbols.rs

@@ -438,6 +438,8 @@ define_symbols! {
     shr,
     simd,
     sized,
+    meta_sized,
+    pointee_sized,
     skip,
     slice_len_fn,
     Some,

crates/test-utils/src/minicore.rs

@@ -26,7 +26,7 @@
 //!     deref: sized
 //!     derive:
 //!     discriminant:
-//!     drop:
+//!     drop: sized
 //!     env: option
 //!     eq: sized
 //!     error: fmt
@@ -37,7 +37,7 @@
 //!     future: pin
 //!     coroutine: pin
 //!     dispatch_from_dyn: unsize, pin
-//!     hash:
+//!     hash: sized
 //!     include:
 //!     index: sized
 //!     infallible:
@@ -80,24 +80,18 @@ pub mod marker {
     #[lang = "pointee_sized"]
     #[fundamental]
     #[rustc_specialization_trait]
-    #[rustc_deny_explicit_impl]
-    #[rustc_do_not_implement_via_object]
     #[rustc_coinductive]
     pub trait PointeeSized {}
 
     #[lang = "meta_sized"]
     #[fundamental]
     #[rustc_specialization_trait]
-    #[rustc_deny_explicit_impl]
-    #[rustc_do_not_implement_via_object]
     #[rustc_coinductive]
     pub trait MetaSized: PointeeSized {}
 
     #[lang = "sized"]
     #[fundamental]
     #[rustc_specialization_trait]
-    #[rustc_deny_explicit_impl]
-    #[rustc_do_not_implement_via_object]
     #[rustc_coinductive]
     pub trait Sized: MetaSized {}
     // endregion:sized
@@ -139,7 +133,7 @@ pub mod marker {
     // endregion:derive
 
     mod copy_impls {
-        use super::Copy;
+        use super::{Copy, PointeeSized};
 
         macro_rules! impl_copy {
             ($($t:ty)*) => {
@@ -225,6 +219,8 @@ pub mod default {
 
 // region:hash
 pub mod hash {
+    use crate::marker::PointeeSized;
+
     pub trait Hasher {}
 
     pub trait Hash: PointeeSized {
@@ -240,6 +236,7 @@ pub mod hash {
 
 // region:cell
 pub mod cell {
+    use crate::marker::PointeeSized;
     use crate::mem;
 
     #[lang = "unsafe_cell"]
@@ -376,7 +373,7 @@ pub mod convert {
     // endregion:from
 
     // region:as_ref
-    pub trait AsRef<T: PointeeSized>: PointeeSized {
+    pub trait AsRef<T: crate::marker::PointeeSized>: crate::marker::PointeeSized {
         fn as_ref(&self) -> &T;
     }
     // endregion:as_ref
@@ -387,6 +384,8 @@ pub mod convert {
 
 pub mod mem {
     // region:manually_drop
+    use crate::marker::PointeeSized;
+
     #[lang = "manually_drop"]
     #[repr(transparent)]
     pub struct ManuallyDrop<T: PointeeSized> {
@@ -447,7 +446,7 @@ pub mod mem {
 pub mod ptr {
     // region:drop
     #[lang = "drop_in_place"]
-    pub unsafe fn drop_in_place<T: PointeeSized>(to_drop: *mut T) {
+    pub unsafe fn drop_in_place<T: crate::marker::PointeeSized>(to_drop: *mut T) {
         unsafe { drop_in_place(to_drop) }
     }
     pub const unsafe fn read<T>(src: *const T) -> T {
@@ -463,20 +462,22 @@ pub mod ptr {
     // region:pointee
     #[lang = "pointee_trait"]
     #[rustc_deny_explicit_impl(implement_via_object = false)]
-    pub trait Pointee: PointeeSized {
+    pub trait Pointee: crate::marker::PointeeSized {
         #[lang = "metadata_type"]
         type Metadata: Copy + Send + Sync + Ord + Hash + Unpin;
     }
     // endregion:pointee
     // region:non_null
     #[rustc_layout_scalar_valid_range_start(1)]
     #[rustc_nonnull_optimization_guaranteed]
-    pub struct NonNull<T: PointeeSized> {
+    pub struct NonNull<T: crate::marker::PointeeSized> {
         pointer: *const T,
     }
     // region:coerce_unsized
-    impl<T: PointeeSized, U: PointeeSized> crate::ops::CoerceUnsized<NonNull<U>> for NonNull<T> where
-        T: crate::marker::Unsize<U>
+    impl<T: crate::marker::PointeeSized, U: crate::marker::PointeeSized>
+        crate::ops::CoerceUnsized<NonNull<U>> for NonNull<T>
+    where
+        T: crate::marker::Unsize<U>,
     {
     }
     // endregion:coerce_unsized
@@ -497,7 +498,7 @@ pub mod ptr {
 pub mod ops {
     // region:coerce_unsized
     mod unsize {
-        use crate::marker::Unsize;
+        use crate::marker::{PointeeSized, Unsize};
 
         #[lang = "coerce_unsized"]
         pub trait CoerceUnsized<T> {}
@@ -519,6 +520,8 @@ pub mod ops {
 
     // region:deref
     mod deref {
+        use crate::marker::PointeeSized;
+
         #[lang = "deref"]
         pub trait Deref: PointeeSized {
             #[lang = "deref_target"]
@@ -1025,7 +1028,7 @@ pub mod ops {
 
     // region:dispatch_from_dyn
     mod dispatch_from_dyn {
-        use crate::marker::Unsize;
+        use crate::marker::{PointeeSized, Unsize};
 
         #[lang = "dispatch_from_dyn"]
         pub trait DispatchFromDyn<T> {}
@@ -1044,6 +1047,8 @@ pub mod ops {
 
 // region:eq
 pub mod cmp {
+    use crate::marker::PointeeSized;
+
     #[lang = "eq"]
     pub trait PartialEq<Rhs: PointeeSized = Self>: PointeeSized {
         fn eq(&self, other: &Rhs) -> bool;
@@ -1090,6 +1095,8 @@ pub mod cmp {
 
 // region:fmt
 pub mod fmt {
+    use crate::marker::PointeeSized;
+
     pub struct Error;
     pub type Result = crate::result::Result<(), Error>;
     pub struct Formatter<'a>;
@@ -1531,6 +1538,8 @@ pub mod iter {
 
     mod traits {
         mod iterator {
+            use crate::marker::PointeeSized;
+
             #[doc(notable_trait)]
             #[lang = "iterator"]
             pub trait Iterator {