Rollup of 6 pull requests

compiler/rustc_lint/src/context.rs

@@ -1245,6 +1245,23 @@ impl<'tcx> LateContext<'tcx> {
 
         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
     }
+
+    /// Returns the associated type `name` for `self_ty` as an implementation of `trait_id`.
+    /// Do not invoke without first verifying that the type implements the trait.
+    pub fn get_associated_type(
+        &self,
+        self_ty: Ty<'tcx>,
+        trait_id: DefId,
+        name: &str,
+    ) -> Option<Ty<'tcx>> {
+        let tcx = self.tcx;
+        tcx.associated_items(trait_id)
+            .find_by_name_and_kind(tcx, Ident::from_str(name), ty::AssocKind::Type, trait_id)
+            .and_then(|assoc| {
+                let proj = tcx.mk_projection(assoc.def_id, tcx.mk_substs_trait(self_ty, []));
+                tcx.try_normalize_erasing_regions(self.param_env, proj).ok()
+            })
+    }
 }
 
 impl<'tcx> abi::HasDataLayout for LateContext<'tcx> {

compiler/rustc_lint/src/deref_into_dyn_supertrait.rs

@@ -0,0 +1,92 @@
+use crate::{LateContext, LateLintPass, LintContext};
+
+use rustc_errors::DelayDm;
+use rustc_hir as hir;
+use rustc_middle::{traits::util::supertraits, ty};
+use rustc_span::sym;
+
+declare_lint! {
+    /// The `deref_into_dyn_supertrait` lint is output whenever there is a use of the
+    /// `Deref` implementation with a `dyn SuperTrait` type as `Output`.
+    ///
+    /// These implementations will become shadowed when the `trait_upcasting` feature is stabilized.
+    /// The `deref` functions will no longer be called implicitly, so there might be behavior change.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(deref_into_dyn_supertrait)]
+    /// #![allow(dead_code)]
+    ///
+    /// use core::ops::Deref;
+    ///
+    /// trait A {}
+    /// trait B: A {}
+    /// impl<'a> Deref for dyn 'a + B {
+    ///     type Target = dyn A;
+    ///     fn deref(&self) -> &Self::Target {
+    ///         todo!()
+    ///     }
+    /// }
+    ///
+    /// fn take_a(_: &dyn A) { }
+    ///
+    /// fn take_b(b: &dyn B) {
+    ///     take_a(b);
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The dyn upcasting coercion feature adds new coercion rules, taking priority
+    /// over certain other coercion rules, which will cause some behavior change.
+    pub DEREF_INTO_DYN_SUPERTRAIT,
+    Warn,
+    "`Deref` implementation usage with a supertrait trait object for output might be shadowed in the future",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #89460 <https://github.com/rust-lang/rust/issues/89460>",
+    };
+}
+
+declare_lint_pass!(DerefIntoDynSupertrait => [DEREF_INTO_DYN_SUPERTRAIT]);
+
+impl<'tcx> LateLintPass<'tcx> for DerefIntoDynSupertrait {
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
+        // `Deref` is being implemented for `t`
+        if let hir::ItemKind::Impl(impl_) = item.kind
+            && let Some(trait_) = &impl_.of_trait
+            && let t = cx.tcx.type_of(item.owner_id)
+            && let opt_did @ Some(did) = trait_.trait_def_id()
+            && opt_did == cx.tcx.lang_items().deref_trait()
+            // `t` is `dyn t_principal`
+            && let ty::Dynamic(data, _, ty::Dyn) = t.kind()
+            && let Some(t_principal) = data.principal()
+            // `<T as Deref>::Target` is `dyn target_principal`
+            && let Some(target) = cx.get_associated_type(t, did, "Target")
+            && let ty::Dynamic(data, _, ty::Dyn) = target.kind()
+            && let Some(target_principal) = data.principal()
+            // `target_principal` is a supertrait of `t_principal`
+            && supertraits(cx.tcx, t_principal.with_self_ty(cx.tcx, cx.tcx.types.trait_object_dummy_self))
+                .any(|sup| sup.map_bound(|x| ty::ExistentialTraitRef::erase_self_ty(cx.tcx, x)) == target_principal)
+        {
+            cx.struct_span_lint(
+                DEREF_INTO_DYN_SUPERTRAIT,
+                cx.tcx.def_span(item.owner_id.def_id),
+                DelayDm(|| {
+                    format!(
+                        "`{t}` implements `Deref` with supertrait `{target_principal}` as target"
+                    )
+                }),
+                |lint| {
+                    if let Some(target_span) = impl_.items.iter().find_map(|i| (i.ident.name == sym::Target).then_some(i.span)) {
+                        lint.span_label(target_span, "target type is set here");
+                    }
+
+                    lint
+                },
+            )
+        }
+    }
+}

compiler/rustc_lint/src/lib.rs

@@ -49,6 +49,7 @@ extern crate tracing;
 mod array_into_iter;
 pub mod builtin;
 mod context;
+mod deref_into_dyn_supertrait;
 mod early;
 mod enum_intrinsics_non_enums;
 mod errors;
@@ -87,6 +88,7 @@ use rustc_span::Span;
 
 use array_into_iter::ArrayIntoIter;
 use builtin::*;
+use deref_into_dyn_supertrait::*;
 use enum_intrinsics_non_enums::EnumIntrinsicsNonEnums;
 use for_loops_over_fallibles::*;
 use hidden_unicode_codepoints::*;
@@ -192,6 +194,7 @@ macro_rules! late_lint_mod_passes {
             $args,
             [
                 ForLoopsOverFallibles: ForLoopsOverFallibles,
+                DerefIntoDynSupertrait: DerefIntoDynSupertrait,
                 HardwiredLints: HardwiredLints,
                 ImproperCTypesDeclarations: ImproperCTypesDeclarations,
                 ImproperCTypesDefinitions: ImproperCTypesDefinitions,

compiler/rustc_lint_defs/src/builtin.rs

@@ -3262,7 +3262,6 @@ declare_lint_pass! {
         UNUSED_TUPLE_STRUCT_FIELDS,
         NON_EXHAUSTIVE_OMITTED_PATTERNS,
         TEXT_DIRECTION_CODEPOINT_IN_COMMENT,
-        DEREF_INTO_DYN_SUPERTRAIT,
         DEPRECATED_CFG_ATTR_CRATE_TYPE_NAME,
         DUPLICATE_MACRO_ATTRIBUTES,
         SUSPICIOUS_AUTO_TRAIT_IMPLS,
@@ -3764,51 +3763,6 @@ declare_lint! {
     "invisible directionality-changing codepoints in comment"
 }
 
-declare_lint! {
-    /// The `deref_into_dyn_supertrait` lint is output whenever there is a use of the
-    /// `Deref` implementation with a `dyn SuperTrait` type as `Output`.
-    ///
-    /// These implementations will become shadowed when the `trait_upcasting` feature is stabilized.
-    /// The `deref` functions will no longer be called implicitly, so there might be behavior change.
-    ///
-    /// ### Example
-    ///
-    /// ```rust,compile_fail
-    /// #![deny(deref_into_dyn_supertrait)]
-    /// #![allow(dead_code)]
-    ///
-    /// use core::ops::Deref;
-    ///
-    /// trait A {}
-    /// trait B: A {}
-    /// impl<'a> Deref for dyn 'a + B {
-    ///     type Target = dyn A;
-    ///     fn deref(&self) -> &Self::Target {
-    ///         todo!()
-    ///     }
-    /// }
-    ///
-    /// fn take_a(_: &dyn A) { }
-    ///
-    /// fn take_b(b: &dyn B) {
-    ///     take_a(b);
-    /// }
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// The dyn upcasting coercion feature adds new coercion rules, taking priority
-    /// over certain other coercion rules, which will cause some behavior change.
-    pub DEREF_INTO_DYN_SUPERTRAIT,
-    Warn,
-    "`Deref` implementation usage with a supertrait trait object for output might be shadowed in the future",
-    @future_incompatible = FutureIncompatibleInfo {
-        reference: "issue #89460 <https://github.com/rust-lang/rust/issues/89460>",
-    };
-}
-
 declare_lint! {
     /// The `duplicate_macro_attributes` lint detects when a `#[test]`-like built-in macro
     /// attribute is duplicated on an item. This lint may trigger on `bench`, `cfg_eval`, `test`

compiler/rustc_middle/src/traits/mod.rs

@@ -651,12 +651,6 @@ pub enum ImplSource<'tcx, N> {
     /// Same as above, but for a function pointer type with the given signature.
     FnPointer(ImplSourceFnPointerData<'tcx, N>),
 
-    /// ImplSource for a builtin `DeterminantKind` trait implementation.
-    DiscriminantKind(ImplSourceDiscriminantKindData),
-
-    /// ImplSource for a builtin `Pointee` trait implementation.
-    Pointee(ImplSourcePointeeData),
-
     /// ImplSource automatically generated for a generator.
     Generator(ImplSourceGeneratorData<'tcx, N>),
 
@@ -678,8 +672,6 @@ impl<'tcx, N> ImplSource<'tcx, N> {
             ImplSource::Generator(c) => c.nested,
             ImplSource::Object(d) => d.nested,
             ImplSource::FnPointer(d) => d.nested,
-            ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData)
-            | ImplSource::Pointee(ImplSourcePointeeData) => vec![],
             ImplSource::TraitAlias(d) => d.nested,
             ImplSource::TraitUpcasting(d) => d.nested,
             ImplSource::ConstDestruct(i) => i.nested,
@@ -696,8 +688,6 @@ impl<'tcx, N> ImplSource<'tcx, N> {
             ImplSource::Generator(c) => &c.nested,
             ImplSource::Object(d) => &d.nested,
             ImplSource::FnPointer(d) => &d.nested,
-            ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData)
-            | ImplSource::Pointee(ImplSourcePointeeData) => &[],
             ImplSource::TraitAlias(d) => &d.nested,
             ImplSource::TraitUpcasting(d) => &d.nested,
             ImplSource::ConstDestruct(i) => &i.nested,
@@ -741,12 +731,6 @@ impl<'tcx, N> ImplSource<'tcx, N> {
                 fn_ty: p.fn_ty,
                 nested: p.nested.into_iter().map(f).collect(),
             }),
-            ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData) => {
-                ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData)
-            }
-            ImplSource::Pointee(ImplSourcePointeeData) => {
-                ImplSource::Pointee(ImplSourcePointeeData)
-            }
             ImplSource::TraitAlias(d) => ImplSource::TraitAlias(ImplSourceTraitAliasData {
                 alias_def_id: d.alias_def_id,
                 substs: d.substs,
@@ -856,13 +840,6 @@ pub struct ImplSourceFnPointerData<'tcx, N> {
     pub nested: Vec<N>,
 }
 
-// FIXME(@lcnr): This should be  refactored and merged with other builtin vtables.
-#[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
-pub struct ImplSourceDiscriminantKindData;
-
-#[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
-pub struct ImplSourcePointeeData;
-
 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
 #[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceConstDestructData<N> {

compiler/rustc_middle/src/traits/select.rs

@@ -105,6 +105,12 @@ pub type EvaluationCache<'tcx> = Cache<
 /// parameter environment.
 #[derive(PartialEq, Eq, Debug, Clone, TypeFoldable, TypeVisitable)]
 pub enum SelectionCandidate<'tcx> {
+    /// A builtin implementation for some specific traits, used in cases
+    /// where we cannot rely an ordinary library implementations.
+    ///
+    /// The most notable examples are `sized`, `Copy` and `Clone`. This is also
+    /// used for the `DiscriminantKind` and `Pointee` trait, both of which have
+    /// an associated type.
     BuiltinCandidate {
         /// `false` if there are no *further* obligations.
         has_nested: bool,
@@ -137,12 +143,6 @@ pub enum SelectionCandidate<'tcx> {
         is_const: bool,
     },
 
-    /// Builtin implementation of `DiscriminantKind`.
-    DiscriminantKindCandidate,
-
-    /// Builtin implementation of `Pointee`.
-    PointeeCandidate,
-
     TraitAliasCandidate,
 
     /// Matching `dyn Trait` with a supertrait of `Trait`. The index is the

compiler/rustc_middle/src/traits/structural_impls.rs

@@ -17,10 +17,6 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSource<'tcx, N> {
 
             super::ImplSource::FnPointer(ref d) => write!(f, "({:?})", d),
 
-            super::ImplSource::DiscriminantKind(ref d) => write!(f, "{:?}", d),
-
-            super::ImplSource::Pointee(ref d) => write!(f, "{:?}", d),
-
             super::ImplSource::Object(ref d) => write!(f, "{:?}", d),
 
             super::ImplSource::Param(ref n, ct) => {
@@ -125,11 +121,3 @@ impl<N: fmt::Debug> fmt::Debug for traits::ImplSourceConstDestructData<N> {
         write!(f, "ImplSourceConstDestructData(nested={:?})", self.nested)
     }
 }
-
-///////////////////////////////////////////////////////////////////////////
-// Lift implementations
-
-TrivialTypeTraversalAndLiftImpls! {
-    super::ImplSourceDiscriminantKindData,
-    super::ImplSourcePointeeData,
-}

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -30,7 +30,7 @@ use rustc_middle::metadata::ModChild;
 use rustc_middle::ty::{self, DefIdTree};
 use rustc_session::cstore::CrateStore;
 use rustc_span::hygiene::{ExpnId, LocalExpnId, MacroKind};
-use rustc_span::source_map::{respan, Spanned};
+use rustc_span::source_map::respan;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::Span;
 
@@ -329,10 +329,12 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
             .iter()
             .map(|field| respan(field.span, field.ident.map_or(kw::Empty, |ident| ident.name)))
             .collect();
-        self.insert_field_names(def_id, field_names);
+        self.r.field_names.insert(def_id, field_names);
     }
 
-    fn insert_field_names(&mut self, def_id: DefId, field_names: Vec<Spanned<Symbol>>) {
+    fn insert_field_names_extern(&mut self, def_id: DefId) {
+        let field_names =
+            self.r.cstore().struct_field_names_untracked(def_id, self.r.session).collect();
         self.r.field_names.insert(def_id, field_names);
     }
 
@@ -995,8 +997,6 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
         let cstore = self.r.cstore();
         match res {
             Res::Def(DefKind::Struct, def_id) => {
-                let field_names =
-                    cstore.struct_field_names_untracked(def_id, self.r.session).collect();
                 if let Some((ctor_kind, ctor_def_id)) = cstore.ctor_untracked(def_id) {
                     let ctor_res = Res::Def(DefKind::Ctor(CtorOf::Struct, ctor_kind), ctor_def_id);
                     let ctor_vis = cstore.visibility_untracked(ctor_def_id);
@@ -1006,13 +1006,9 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                         .struct_constructors
                         .insert(def_id, (ctor_res, ctor_vis, field_visibilities));
                 }
-                self.insert_field_names(def_id, field_names);
-            }
-            Res::Def(DefKind::Union, def_id) => {
-                let field_names =
-                    cstore.struct_field_names_untracked(def_id, self.r.session).collect();
-                self.insert_field_names(def_id, field_names);
+                self.insert_field_names_extern(def_id)
             }
+            Res::Def(DefKind::Union, def_id) => self.insert_field_names_extern(def_id),
             Res::Def(DefKind::AssocFn, def_id) => {
                 if cstore.fn_has_self_parameter_untracked(def_id, self.r.session) {
                     self.r.has_self.insert(def_id);
@@ -1514,20 +1510,16 @@ impl<'a, 'b> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b> {
         };
 
         // Define a constructor name in the value namespace.
-        let fields_id = if let Some((ctor_kind, ctor_node_id)) = CtorKind::from_ast(&variant.data) {
+        if let Some((ctor_kind, ctor_node_id)) = CtorKind::from_ast(&variant.data) {
             let ctor_def_id = self.r.local_def_id(ctor_node_id);
             let ctor_res =
                 Res::Def(DefKind::Ctor(CtorOf::Variant, ctor_kind), ctor_def_id.to_def_id());
             self.r.define(parent, ident, ValueNS, (ctor_res, ctor_vis, variant.span, expn_id));
             self.r.visibilities.insert(ctor_def_id, ctor_vis);
-            ctor_def_id
-        } else {
-            def_id
-        };
+        }
 
         // Record field names for error reporting.
-        // FIXME: Always use non-ctor id as the key.
-        self.insert_field_names_local(fields_id.to_def_id(), &variant.data);
+        self.insert_field_names_local(def_id.to_def_id(), &variant.data);
 
         visit::walk_variant(self, variant);
     }