Remove PointerLike trait

compiler-errors · compiler-errors · commit e2e3f5809b07 · 2025-07-03T20:03:49.000Z
diff --git a/compiler/rustc_abi/src/layout/ty.rs b/compiler/rustc_abi/src/layout/ty.rs
@@ -6,7 +6,7 @@ use rustc_macros::HashStable_Generic;
 
 use crate::{
     AbiAlign, Align, BackendRepr, FieldsShape, Float, HasDataLayout, LayoutData, Niche,
-    PointeeInfo, Primitive, Scalar, Size, TargetDataLayout, Variants,
+    PointeeInfo, Primitive, Size, Variants,
 };
 
 // Explicitly import `Float` to avoid ambiguity with `Primitive::Float`.
@@ -115,16 +115,6 @@ impl<'a> Layout<'a> {
     pub fn unadjusted_abi_align(self) -> Align {
         self.0.0.unadjusted_abi_align
     }
-
-    /// Whether the layout is from a type that implements [`std::marker::PointerLike`].
-    ///
-    /// Currently, that means that the type is pointer-sized, pointer-aligned,
-    /// and has a initialized (non-union), scalar ABI.
-    pub fn is_pointer_like(self, data_layout: &TargetDataLayout) -> bool {
-        self.size() == data_layout.pointer_size
-            && self.align().abi == data_layout.pointer_align.abi
-            && matches!(self.backend_repr(), BackendRepr::Scalar(Scalar::Initialized { .. }))
-    }
 }
 
 /// The layout of a type, alongside the type itself.
diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
@@ -367,8 +367,6 @@ language_item_table! {
     TryTraitBranch,          sym::branch,              branch_fn,                  Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
     TryTraitFromYeet,        sym::from_yeet,           from_yeet_fn,               Target::Fn,             GenericRequirement::None;
 
-    PointerLike,             sym::pointer_like,        pointer_like,               Target::Trait,          GenericRequirement::Exact(0);
-
     CoercePointeeValidated, sym::coerce_pointee_validated, coerce_pointee_validated_trait, Target::Trait,     GenericRequirement::Exact(0);
 
     ConstParamTy,            sym::const_param_ty,      const_param_ty_trait,       Target::Trait,          GenericRequirement::Exact(0);
diff --git a/compiler/rustc_hir_analysis/src/coherence/builtin.rs b/compiler/rustc_hir_analysis/src/coherence/builtin.rs
@@ -47,7 +47,6 @@ pub(super) fn check_trait<'tcx>(
     checker.check(lang_items.coerce_unsized_trait(), visit_implementation_of_coerce_unsized)?;
     checker
         .check(lang_items.dispatch_from_dyn_trait(), visit_implementation_of_dispatch_from_dyn)?;
-    checker.check(lang_items.pointer_like(), visit_implementation_of_pointer_like)?;
     checker.check(
         lang_items.coerce_pointee_validated_trait(),
         visit_implementation_of_coerce_pointee_validity,
@@ -707,104 +706,6 @@ fn infringing_fields_error<'tcx>(
     err.emit()
 }
 
-fn visit_implementation_of_pointer_like(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> {
-    let tcx = checker.tcx;
-    let typing_env = ty::TypingEnv::non_body_analysis(tcx, checker.impl_def_id);
-    let impl_span = tcx.def_span(checker.impl_def_id);
-    let self_ty = tcx.impl_trait_ref(checker.impl_def_id).unwrap().instantiate_identity().self_ty();
-
-    let is_permitted_primitive = match *self_ty.kind() {
-        ty::Adt(def, _) => def.is_box(),
-        ty::Uint(..) | ty::Int(..) | ty::RawPtr(..) | ty::Ref(..) | ty::FnPtr(..) => true,
-        _ => false,
-    };
-
-    if is_permitted_primitive
-        && let Ok(layout) = tcx.layout_of(typing_env.as_query_input(self_ty))
-        && layout.layout.is_pointer_like(&tcx.data_layout)
-    {
-        return Ok(());
-    }
-
-    let why_disqualified = match *self_ty.kind() {
-        // If an ADT is repr(transparent)
-        ty::Adt(self_ty_def, args) => {
-            if self_ty_def.repr().transparent() {
-                // FIXME(compiler-errors): This should and could be deduplicated into a query.
-                // Find the nontrivial field.
-                let adt_typing_env = ty::TypingEnv::non_body_analysis(tcx, self_ty_def.did());
-                let nontrivial_field = self_ty_def.all_fields().find(|field_def| {
-                    let field_ty = tcx.type_of(field_def.did).instantiate_identity();
-                    !tcx.layout_of(adt_typing_env.as_query_input(field_ty))
-                        .is_ok_and(|layout| layout.layout.is_1zst())
-                });
-
-                if let Some(nontrivial_field) = nontrivial_field {
-                    // Check that the nontrivial field implements `PointerLike`.
-                    let nontrivial_field_ty = nontrivial_field.ty(tcx, args);
-                    let (infcx, param_env) = tcx.infer_ctxt().build_with_typing_env(typing_env);
-                    let ocx = ObligationCtxt::new(&infcx);
-                    ocx.register_bound(
-                        ObligationCause::misc(impl_span, checker.impl_def_id),
-                        param_env,
-                        nontrivial_field_ty,
-                        tcx.require_lang_item(LangItem::PointerLike, impl_span),
-                    );
-                    // FIXME(dyn-star): We should regionck this implementation.
-                    if ocx.select_all_or_error().is_empty() {
-                        return Ok(());
-                    } else {
-                        format!(
-                            "the field `{field_name}` of {descr} `{self_ty}` \
-                    does not implement `PointerLike`",
-                            field_name = nontrivial_field.name,
-                            descr = self_ty_def.descr()
-                        )
-                    }
-                } else {
-                    format!(
-                        "the {descr} `{self_ty}` is `repr(transparent)`, \
-                but does not have a non-trivial field (it is zero-sized)",
-                        descr = self_ty_def.descr()
-                    )
-                }
-            } else if self_ty_def.is_box() {
-                // If we got here, then the `layout.is_pointer_like()` check failed
-                // and this box is not a thin pointer.
-
-                String::from("boxes of dynamically-sized types are too large to be `PointerLike`")
-            } else {
-                format!(
-                    "the {descr} `{self_ty}` is not `repr(transparent)`",
-                    descr = self_ty_def.descr()
-                )
-            }
-        }
-        ty::Ref(..) => {
-            // If we got here, then the `layout.is_pointer_like()` check failed
-            // and this reference is not a thin pointer.
-            String::from("references to dynamically-sized types are too large to be `PointerLike`")
-        }
-        ty::Dynamic(..) | ty::Foreign(..) => {
-            String::from("types of dynamic or unknown size may not implement `PointerLike`")
-        }
-        _ => {
-            // This is a white lie; it is true everywhere outside the standard library.
-            format!("only user-defined sized types are eligible for `impl PointerLike`")
-        }
-    };
-
-    Err(tcx
-        .dcx()
-        .struct_span_err(
-            impl_span,
-            "implementation must be applied to type that has the same ABI as a pointer, \
-            or is `repr(transparent)` and whose field is `PointerLike`",
-        )
-        .with_note(why_disqualified)
-        .emit())
-}
-
 fn visit_implementation_of_coerce_pointee_validity(
     checker: &Checker<'_>,
 ) -> Result<(), ErrorGuaranteed> {
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
@@ -1149,12 +1149,16 @@ impl<'tcx> TypingEnv<'tcx> {
     {
         // FIXME(#132279): We should assert that the value does not contain any placeholders
         // as these placeholders are also local to the current inference context. However, we
-        // currently use pseudo-canonical queries in the trait solver which replaces params with
-        // placeholders. We should also simply not use pseudo-canonical queries in the trait
-        // solver, at which point we can readd this assert. As of writing this comment, this is
-        // only used by `fn layout_is_pointer_like` when calling `layout_of`.
+        // currently use pseudo-canonical queries in the trait solver, which replaces params
+        // with placeholders during canonicalization. We should also simply not use pseudo-
+        // canonical queries in the trait solver, at which point we can readd this assert.
         //
-        // debug_assert!(!value.has_placeholders());
+        // As of writing this comment, this is only used when normalizing consts that mention
+        // params.
+        /* debug_assert!(
+            !value.has_placeholders(),
+            "{value:?} which has placeholder shouldn't be pseudo-canonicalized"
+        ); */
         PseudoCanonicalInput { typing_env: self, value }
     }
 }
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
@@ -1623,7 +1623,6 @@ symbols! {
         pointee_sized,
         pointee_trait,
         pointer,
-        pointer_like,
         poll,
         poll_next,
         position,
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -14,9 +14,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_infer::infer::{BoundRegionConversionTime, DefineOpaqueTypes, InferOk};
 use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::traits::{BuiltinImplSource, SignatureMismatchData};
-use rustc_middle::ty::{
-    self, GenericArgsRef, Region, SizedTraitKind, Ty, TyCtxt, Upcast, elaborate,
-};
+use rustc_middle::ty::{self, GenericArgsRef, Region, SizedTraitKind, Ty, TyCtxt, Upcast};
 use rustc_middle::{bug, span_bug};
 use rustc_span::def_id::DefId;
 use thin_vec::thin_vec;
@@ -1147,38 +1145,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     ty::ClauseKind::TypeOutlives(outlives).upcast(tcx),
                 ));
 
-                // Require that all AFIT will return something that can be coerced into `dyn*`
-                // -- a shim will be responsible for doing the actual coercion to `dyn*`.
-                if let Some(principal) = data.principal() {
-                    for supertrait in
-                        elaborate::supertraits(tcx, principal.with_self_ty(tcx, source))
-                    {
-                        if tcx.is_trait_alias(supertrait.def_id()) {
-                            continue;
-                        }
-
-                        for &assoc_item in tcx.associated_item_def_ids(supertrait.def_id()) {
-                            if !tcx.is_impl_trait_in_trait(assoc_item) {
-                                continue;
-                            }
-
-                            // RPITITs with `Self: Sized` don't need to be checked.
-                            if tcx.generics_require_sized_self(assoc_item) {
-                                continue;
-                            }
-
-                            let pointer_like_goal = pointer_like_goal_for_rpitit(
-                                tcx,
-                                supertrait,
-                                assoc_item,
-                                &obligation.cause,
-                            );
-
-                            nested.push(predicate_to_obligation(pointer_like_goal.upcast(tcx)));
-                        }
-                    }
-                }
-
                 ImplSource::Builtin(BuiltinImplSource::Misc, nested)
             }
 
@@ -1344,46 +1310,3 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         ImplSource::Builtin(BuiltinImplSource::Misc, obligations)
     }
 }
-
-/// Compute a goal that some RPITIT (right now, only RPITITs corresponding to Futures)
-/// implements the `PointerLike` trait, which is a requirement for the RPITIT to be
-/// coercible to `dyn* Future`, which is itself a requirement for the RPITIT's parent
-/// trait to be coercible to `dyn Trait`.
-///
-/// We do this given a supertrait's substitutions, and then augment the substitutions
-/// with bound variables to compute the goal universally. Given that `PointerLike` has
-/// no region requirements (at least for the built-in pointer types), this shouldn't
-/// *really* matter, but it is the best choice for soundness.
-fn pointer_like_goal_for_rpitit<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    supertrait: ty::PolyTraitRef<'tcx>,
-    rpitit_item: DefId,
-    cause: &ObligationCause<'tcx>,
-) -> ty::PolyTraitRef<'tcx> {
-    let mut bound_vars = supertrait.bound_vars().to_vec();
-
-    let args = supertrait.skip_binder().args.extend_to(tcx, rpitit_item, |arg, _| match arg.kind {
-        ty::GenericParamDefKind::Lifetime => {
-            let kind = ty::BoundRegionKind::Named(arg.def_id, tcx.item_name(arg.def_id));
-            bound_vars.push(ty::BoundVariableKind::Region(kind));
-            ty::Region::new_bound(
-                tcx,
-                ty::INNERMOST,
-                ty::BoundRegion { var: ty::BoundVar::from_usize(bound_vars.len() - 1), kind },
-            )
-            .into()
-        }
-        ty::GenericParamDefKind::Type { .. } | ty::GenericParamDefKind::Const { .. } => {
-            unreachable!()
-        }
-    });
-
-    ty::Binder::bind_with_vars(
-        ty::TraitRef::new(
-            tcx,
-            tcx.require_lang_item(LangItem::PointerLike, cause.span),
-            [Ty::new_projection_from_args(tcx, rpitit_item, args)],
-        ),
-        tcx.mk_bound_variable_kinds(&bound_vars),
-    )
-}
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
@@ -191,7 +191,7 @@ use core::error::{self, Error};
 use core::fmt;
 use core::future::Future;
 use core::hash::{Hash, Hasher};
-use core::marker::{PointerLike, Tuple, Unsize};
+use core::marker::{Tuple, Unsize};
 use core::mem::{self, SizedTypeProperties};
 use core::ops::{
     AsyncFn, AsyncFnMut, AsyncFnOnce, CoerceUnsized, Coroutine, CoroutineState, Deref, DerefMut,
@@ -2132,6 +2132,3 @@ impl<E: Error> Error for Box<E> {
         Error::provide(&**self, request);
     }
 }
-
-#[unstable(feature = "pointer_like_trait", issue = "none")]
-impl<T> PointerLike for Box<T> {}
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
@@ -134,7 +134,6 @@
 #![feature(panic_internals)]
 #![feature(pattern)]
 #![feature(pin_coerce_unsized_trait)]
-#![feature(pointer_like_trait)]
 #![feature(ptr_alignment_type)]
 #![feature(ptr_internals)]
 #![feature(ptr_metadata)]
diff --git a/library/core/src/cell.rs b/library/core/src/cell.rs
@@ -252,7 +252,7 @@
 
 use crate::cmp::Ordering;
 use crate::fmt::{self, Debug, Display};
-use crate::marker::{PhantomData, PointerLike, Unsize};
+use crate::marker::{PhantomData, Unsize};
 use crate::mem;
 use crate::ops::{CoerceUnsized, Deref, DerefMut, DerefPure, DispatchFromDyn};
 use crate::panic::const_panic;
@@ -669,9 +669,6 @@ impl<T: CoerceUnsized<U>, U> CoerceUnsized<Cell<U>> for Cell<T> {}
 #[unstable(feature = "dispatch_from_dyn", issue = "none")]
 impl<T: DispatchFromDyn<U>, U> DispatchFromDyn<Cell<U>> for Cell<T> {}
 
-#[unstable(feature = "pointer_like_trait", issue = "none")]
-impl<T: PointerLike> PointerLike for Cell<T> {}
-
 impl<T> Cell<[T]> {
     /// Returns a `&[Cell<T>]` from a `&Cell<[T]>`
     ///
@@ -2361,9 +2358,6 @@ impl<T: CoerceUnsized<U>, U> CoerceUnsized<UnsafeCell<U>> for UnsafeCell<T> {}
 #[unstable(feature = "dispatch_from_dyn", issue = "none")]
 impl<T: DispatchFromDyn<U>, U> DispatchFromDyn<UnsafeCell<U>> for UnsafeCell<T> {}
 
-#[unstable(feature = "pointer_like_trait", issue = "none")]
-impl<T: PointerLike> PointerLike for UnsafeCell<T> {}
-
 /// [`UnsafeCell`], but [`Sync`].
 ///
 /// This is just an `UnsafeCell`, except it implements `Sync`
@@ -2470,9 +2464,6 @@ impl<T: CoerceUnsized<U>, U> CoerceUnsized<SyncUnsafeCell<U>> for SyncUnsafeCell
 //#[unstable(feature = "sync_unsafe_cell", issue = "95439")]
 impl<T: DispatchFromDyn<U>, U> DispatchFromDyn<SyncUnsafeCell<U>> for SyncUnsafeCell<T> {}
 
-#[unstable(feature = "pointer_like_trait", issue = "none")]
-impl<T: PointerLike> PointerLike for SyncUnsafeCell<T> {}
-
 #[allow(unused)]
 fn assert_coerce_unsized(
     a: UnsafeCell<&i32>,
diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs
@@ -1066,37 +1066,6 @@ pub trait Destruct {}
 #[rustc_do_not_implement_via_object]
 pub trait Tuple {}
 
-/// A marker for pointer-like types.
-///
-/// This trait can only be implemented for types that are certain to have
-/// the same size and alignment as a [`usize`] or [`*const ()`](pointer).
-/// To ensure this, there are special requirements on implementations
-/// of `PointerLike` (other than the already-provided implementations
-/// for built-in types):
-///
-/// * The type must have `#[repr(transparent)]`.
-/// * The type’s sole non-zero-sized field must itself implement `PointerLike`.
-#[unstable(feature = "pointer_like_trait", issue = "none")]
-#[lang = "pointer_like"]
-#[diagnostic::on_unimplemented(
-    message = "`{Self}` needs to have the same ABI as a pointer",
-    label = "`{Self}` needs to be a pointer-like type"
-)]
-#[rustc_do_not_implement_via_object]
-pub trait PointerLike {}
-
-marker_impls! {
-    #[unstable(feature = "pointer_like_trait", issue = "none")]
-    PointerLike for
-        isize,
-        usize,
-        {T} &T,
-        {T} &mut T,
-        {T} *const T,
-        {T} *mut T,
-        {T: PointerLike} crate::pin::Pin<T>,
-}
-
 /// A marker for types which can be used as types of `const` generic parameters.
 ///
 /// These types must have a proper equivalence relation (`Eq`) and it must be automatically
diff --git a/library/core/src/pin/unsafe_pinned.rs b/library/core/src/pin/unsafe_pinned.rs
@@ -1,5 +1,5 @@
 use crate::cell::UnsafeCell;
-use crate::marker::{PointerLike, Unpin};
+use crate::marker::Unpin;
 use crate::ops::{CoerceUnsized, DispatchFromDyn};
 use crate::pin::Pin;
 use crate::{fmt, ptr};
@@ -178,8 +178,4 @@ impl<T: CoerceUnsized<U>, U> CoerceUnsized<UnsafePinned<U>> for UnsafePinned<T>
 // #[unstable(feature = "unsafe_pinned", issue = "125735")]
 impl<T: DispatchFromDyn<U>, U> DispatchFromDyn<UnsafePinned<U>> for UnsafePinned<T> {}
 
-#[unstable(feature = "pointer_like_trait", issue = "none")]
-// #[unstable(feature = "unsafe_pinned", issue = "125735")]
-impl<T: PointerLike> PointerLike for UnsafePinned<T> {}
-
 // FIXME(unsafe_pinned): impl PinCoerceUnsized for UnsafePinned<T>?
diff --git a/library/core/src/ptr/non_null.rs b/library/core/src/ptr/non_null.rs
diff --git a/tests/ui/traits/next-solver/pointer-like.rs b/tests/ui/traits/next-solver/pointer-like.rs
diff --git a/tests/ui/traits/next-solver/pointer-like.stderr b/tests/ui/traits/next-solver/pointer-like.stderr
