Rollup merge of #122043 - Y-Nak:move-early-binder, r=lcnr

Apply `EarlyBinder` only to `TraitRef` in `ImplTraitHeader`

Resolves #121852

This PR
1. Moves `EarlyBinder` to `TraitRef` inside `ImplTraitHeader`,
2. Changes visibility of `coherence::builtin::check_trait` to `pub(super)` from `pub` as it seems not being re-exported from the `coherence` module.

Author: GuillaumeGomez

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -1612,10 +1612,11 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         .any(|impl_def_id| {
                             let impl_header = tcx.impl_trait_header(impl_def_id);
                             impl_header.is_some_and(|header| {
-                                let header = header.instantiate(
+                                let trait_ref = header.trait_ref.instantiate(
                                     tcx,
                                     infcx.fresh_args_for_item(DUMMY_SP, impl_def_id),
                                 );
+
                                 let value = tcx.fold_regions(qself_ty, |_, _| tcx.lifetimes.re_erased);
                                 // FIXME: Don't bother dealing with non-lifetime binders here...
                                 if value.has_escaping_bound_vars() {
@@ -1624,7 +1625,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                 infcx
                                     .can_eq(
                                         ty::ParamEnv::empty(),
-                                        header.trait_ref.self_ty(),
+                                        trait_ref.self_ty(),
                                         value,
                                     ) && header.polarity != ty::ImplPolarity::Negative
                             })
@@ -1677,9 +1678,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     .filter(|header| {
                         // Consider only accessible traits
                         tcx.visibility(trait_def_id).is_accessible_from(self.item_def_id(), tcx)
-                            && header.skip_binder().polarity != ty::ImplPolarity::Negative
+                            && header.polarity != ty::ImplPolarity::Negative
                     })
-                    .map(|header| header.instantiate_identity().trait_ref.self_ty())
+                    .map(|header| header.trait_ref.instantiate_identity().self_ty())
                     // We don't care about blanket impls.
                     .filter(|self_ty| !self_ty.has_non_region_param())
                     .map(|self_ty| tcx.erase_regions(self_ty).to_string())

compiler/rustc_hir_analysis/src/check/check.rs

@@ -530,11 +530,7 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
         }
         DefKind::Impl { of_trait } => {
             if of_trait && let Some(impl_trait_header) = tcx.impl_trait_header(def_id) {
-                check_impl_items_against_trait(
-                    tcx,
-                    def_id,
-                    impl_trait_header.instantiate_identity(),
-                );
+                check_impl_items_against_trait(tcx, def_id, impl_trait_header);
                 check_on_unimplemented(tcx, def_id);
             }
         }
@@ -725,10 +721,11 @@ fn check_impl_items_against_trait<'tcx>(
     impl_id: LocalDefId,
     impl_trait_header: ty::ImplTraitHeader<'tcx>,
 ) {
+    let trait_ref = impl_trait_header.trait_ref.instantiate_identity();
     // If the trait reference itself is erroneous (so the compilation is going
     // to fail), skip checking the items here -- the `impl_item` table in `tcx`
     // isn't populated for such impls.
-    if impl_trait_header.references_error() {
+    if trait_ref.references_error() {
         return;
     }
 
@@ -752,7 +749,7 @@ fn check_impl_items_against_trait<'tcx>(
         }
     }
 
-    let trait_def = tcx.trait_def(impl_trait_header.trait_ref.def_id);
+    let trait_def = tcx.trait_def(trait_ref.def_id);
 
     for &impl_item in impl_item_refs {
         let ty_impl_item = tcx.associated_item(impl_item);
@@ -771,10 +768,10 @@ fn check_impl_items_against_trait<'tcx>(
                 ));
             }
             ty::AssocKind::Fn => {
-                compare_impl_method(tcx, ty_impl_item, ty_trait_item, impl_trait_header.trait_ref);
+                compare_impl_method(tcx, ty_impl_item, ty_trait_item, trait_ref);
             }
             ty::AssocKind::Type => {
-                compare_impl_ty(tcx, ty_impl_item, ty_trait_item, impl_trait_header.trait_ref);
+                compare_impl_ty(tcx, ty_impl_item, ty_trait_item, trait_ref);
             }
         }
 
@@ -794,7 +791,7 @@ fn check_impl_items_against_trait<'tcx>(
         let mut must_implement_one_of: Option<&[Ident]> =
             trait_def.must_implement_one_of.as_deref();
 
-        for &trait_item_id in tcx.associated_item_def_ids(impl_trait_header.trait_ref.def_id) {
+        for &trait_item_id in tcx.associated_item_def_ids(trait_ref.def_id) {
             let leaf_def = ancestors.leaf_def(tcx, trait_item_id);
 
             let is_implemented = leaf_def
@@ -872,7 +869,7 @@ fn check_impl_items_against_trait<'tcx>(
 
         if let Some(missing_items) = must_implement_one_of {
             let attr_span = tcx
-                .get_attr(impl_trait_header.trait_ref.def_id, sym::rustc_must_implement_one_of)
+                .get_attr(trait_ref.def_id, sym::rustc_must_implement_one_of)
                 .map(|attr| attr.span);
 
             missing_items_must_implement_one_of_err(

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -247,7 +247,7 @@ fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) -> Result<()
         hir::ItemKind::Impl(impl_) => {
             let header = tcx.impl_trait_header(def_id);
             let is_auto = header
-                .is_some_and(|header| tcx.trait_is_auto(header.skip_binder().trait_ref.def_id));
+                .is_some_and(|header| tcx.trait_is_auto(header.trait_ref.skip_binder().def_id));
 
             crate::impl_wf_check::check_impl_wf(tcx, def_id)?;
             let mut res = Ok(());
@@ -261,7 +261,7 @@ fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) -> Result<()
                     .emit());
             }
             // We match on both `ty::ImplPolarity` and `ast::ImplPolarity` just to get the `!` span.
-            match header.map(|h| h.skip_binder().polarity) {
+            match header.map(|h| h.polarity) {
                 // `None` means this is an inherent impl
                 Some(ty::ImplPolarity::Positive) | None => {
                     res = res.and(check_impl(tcx, item, impl_.self_ty, &impl_.of_trait));

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -25,7 +25,7 @@ use rustc_trait_selection::traits::ObligationCtxt;
 use rustc_trait_selection::traits::{self, ObligationCause};
 use std::collections::BTreeMap;
 
-pub fn check_trait<'tcx>(
+pub(super) fn check_trait<'tcx>(
     tcx: TyCtxt<'tcx>,
     trait_def_id: DefId,
     impl_def_id: LocalDefId,
@@ -66,10 +66,9 @@ impl<'tcx> Checker<'tcx> {
 
 fn visit_implementation_of_drop(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> {
     let tcx = checker.tcx;
-    let header = checker.impl_header;
     let impl_did = checker.impl_def_id;
     // Destructors only work on local ADT types.
-    match header.trait_ref.self_ty().kind() {
+    match checker.impl_header.trait_ref.instantiate_identity().self_ty().kind() {
         ty::Adt(def, _) if def.did().is_local() => return Ok(()),
         ty::Error(_) => return Ok(()),
         _ => {}
@@ -86,7 +85,7 @@ fn visit_implementation_of_copy(checker: &Checker<'_>) -> Result<(), ErrorGuaran
     let impl_did = checker.impl_def_id;
     debug!("visit_implementation_of_copy: impl_did={:?}", impl_did);
 
-    let self_type = impl_header.trait_ref.self_ty();
+    let self_type = impl_header.trait_ref.instantiate_identity().self_ty();
     debug!("visit_implementation_of_copy: self_type={:?} (bound)", self_type);
 
     let param_env = tcx.param_env(impl_did);
@@ -120,7 +119,7 @@ fn visit_implementation_of_const_param_ty(checker: &Checker<'_>) -> Result<(), E
     let tcx = checker.tcx;
     let header = checker.impl_header;
     let impl_did = checker.impl_def_id;
-    let self_type = header.trait_ref.self_ty();
+    let self_type = header.trait_ref.instantiate_identity().self_ty();
     assert!(!self_type.has_escaping_bound_vars());
 
     let param_env = tcx.param_env(impl_did);
@@ -157,9 +156,8 @@ fn visit_implementation_of_coerce_unsized(checker: &Checker<'_>) -> Result<(), E
 
 fn visit_implementation_of_dispatch_from_dyn(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> {
     let tcx = checker.tcx;
-    let header = checker.impl_header;
     let impl_did = checker.impl_def_id;
-    let trait_ref = header.trait_ref;
+    let trait_ref = checker.impl_header.trait_ref.instantiate_identity();
     debug!("visit_implementation_of_dispatch_from_dyn: impl_did={:?}", impl_did);
 
     let span = tcx.def_span(impl_did);

compiler/rustc_hir_analysis/src/coherence/mod.rs

@@ -134,11 +134,12 @@ fn coherent_trait(tcx: TyCtxt<'_>, def_id: DefId) -> Result<(), ErrorGuaranteed>
     let mut res = tcx.ensure().specialization_graph_of(def_id);
 
     for &impl_def_id in impls {
-        let trait_header = tcx.impl_trait_header(impl_def_id).unwrap().instantiate_identity();
-        let trait_def = tcx.trait_def(trait_header.trait_ref.def_id);
+        let trait_header = tcx.impl_trait_header(impl_def_id).unwrap();
+        let trait_ref = trait_header.trait_ref.instantiate_identity();
+        let trait_def = tcx.trait_def(trait_ref.def_id);
 
-        res = res.and(check_impl(tcx, impl_def_id, trait_header.trait_ref, trait_def));
-        res = res.and(check_object_overlap(tcx, impl_def_id, trait_header.trait_ref));
+        res = res.and(check_impl(tcx, impl_def_id, trait_ref, trait_def));
+        res = res.and(check_object_overlap(tcx, impl_def_id, trait_ref));
 
         res = res.and(unsafety::check_item(tcx, impl_def_id, trait_header, trait_def));
         res = res.and(tcx.ensure().orphan_check_impl(impl_def_id));

compiler/rustc_hir_analysis/src/coherence/unsafety.rs

@@ -13,9 +13,10 @@ pub(super) fn check_item(
     trait_header: ImplTraitHeader<'_>,
     trait_def: &TraitDef,
 ) -> Result<(), ErrorGuaranteed> {
-    let trait_ref = trait_header.trait_ref;
     let unsafe_attr =
         tcx.generics_of(def_id).params.iter().find(|p| p.pure_wrt_drop).map(|_| "may_dangle");
+    let trait_ref = trait_header.trait_ref.instantiate_identity();
+
     match (trait_def.unsafety, unsafe_attr, trait_header.unsafety, trait_header.polarity) {
         (Unsafety::Normal, None, Unsafety::Unsafe, Positive | Reservation) => {
             let span = tcx.def_span(def_id);

compiler/rustc_hir_analysis/src/collect.rs

@@ -1519,10 +1519,7 @@ fn suggest_impl_trait<'tcx>(
     None
 }
 
-fn impl_trait_header(
-    tcx: TyCtxt<'_>,
-    def_id: LocalDefId,
-) -> Option<ty::EarlyBinder<ty::ImplTraitHeader<'_>>> {
+fn impl_trait_header(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ty::ImplTraitHeader<'_>> {
     let icx = ItemCtxt::new(tcx, def_id);
     let item = tcx.hir().expect_item(def_id);
     let impl_ = item.expect_impl();
@@ -1558,11 +1555,11 @@ fn impl_trait_header(
             } else {
                 icx.astconv().instantiate_mono_trait_ref(ast_trait_ref, selfty)
             };
-            ty::EarlyBinder::bind(ty::ImplTraitHeader {
-                trait_ref,
+            ty::ImplTraitHeader {
+                trait_ref: ty::EarlyBinder::bind(trait_ref),
                 unsafety: impl_.unsafety,
                 polarity: polarity_of_impl(tcx, def_id,  impl_, item.span)
-            })
+            }
         })
 }
 

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -3368,11 +3368,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 "inherent impls can't be candidates, only trait impls can be",
                             )
                         })
-                        .filter(|header| {
-                            header.skip_binder().polarity == ty::ImplPolarity::Negative
-                        })
+                        .filter(|header| header.polarity == ty::ImplPolarity::Negative)
                         .any(|header| {
-                            let imp = header.instantiate_identity().trait_ref;
+                            let imp = header.trait_ref.instantiate_identity();
                             let imp_simp =
                                 simplify_type(self.tcx, imp.self_ty(), TreatParams::ForLookup);
                             imp_simp.is_some_and(|s| s == simp_rcvr_ty)

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1993,9 +1993,8 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 
             if of_trait && let Some(header) = tcx.impl_trait_header(def_id) {
                 record!(self.tables.impl_trait_header[def_id] <- header);
-                let trait_ref = header.map_bound(|h| h.trait_ref);
 
-                let trait_ref = trait_ref.instantiate_identity();
+                let trait_ref = header.trait_ref.instantiate_identity();
                 let simplified_self_ty = fast_reject::simplify_type(
                     self.tcx,
                     trait_ref.self_ty(),

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -423,7 +423,7 @@ define_tables! {
     variances_of: Table<DefIndex, LazyArray<ty::Variance>>,
     fn_sig: Table<DefIndex, LazyValue<ty::EarlyBinder<ty::PolyFnSig<'static>>>>,
     codegen_fn_attrs: Table<DefIndex, LazyValue<CodegenFnAttrs>>,
-    impl_trait_header: Table<DefIndex, LazyValue<ty::EarlyBinder<ty::ImplTraitHeader<'static>>>>,
+    impl_trait_header: Table<DefIndex, LazyValue<ty::ImplTraitHeader<'static>>>,
     const_param_default: Table<DefIndex, LazyValue<ty::EarlyBinder<rustc_middle::ty::Const<'static>>>>,
     object_lifetime_default: Table<DefIndex, LazyValue<ObjectLifetimeDefault>>,
     optimized_mir: Table<DefIndex, LazyValue<mir::Body<'static>>>,

compiler/rustc_middle/src/query/erase.rs

@@ -177,8 +177,8 @@ impl EraseType for Option<mir::DestructuredConstant<'_>> {
     type Result = [u8; size_of::<Option<mir::DestructuredConstant<'static>>>()];
 }
 
-impl EraseType for Option<ty::EarlyBinder<ty::ImplTraitHeader<'_>>> {
-    type Result = [u8; size_of::<Option<ty::EarlyBinder<ty::ImplTraitHeader<'static>>>>()];
+impl EraseType for Option<ty::ImplTraitHeader<'_>> {
+    type Result = [u8; size_of::<Option<ty::ImplTraitHeader<'static>>>()];
 }
 
 impl EraseType for Option<ty::EarlyBinder<Ty<'_>>> {

compiler/rustc_middle/src/query/mod.rs

@@ -840,7 +840,7 @@ rustc_queries! {
 
     /// Given an `impl_id`, return the trait it implements along with some header information.
     /// Return `None` if this is an inherent impl.
-    query impl_trait_header(impl_id: DefId) -> Option<ty::EarlyBinder<ty::ImplTraitHeader<'tcx>>> {
+    query impl_trait_header(impl_id: DefId) -> Option<ty::ImplTraitHeader<'tcx>> {
         desc { |tcx| "computing trait implemented by `{}`", tcx.def_path_str(impl_id) }
         cache_on_disk_if { impl_id.is_local() }
         separate_provide_extern

compiler/rustc_middle/src/ty/context.rs

@@ -2310,12 +2310,11 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         def_id: impl IntoQueryParam<DefId>,
     ) -> Option<ty::EarlyBinder<ty::TraitRef<'tcx>>> {
-        Some(self.impl_trait_header(def_id)?.map_bound(|h| h.trait_ref))
+        Some(self.impl_trait_header(def_id)?.trait_ref)
     }
 
     pub fn impl_polarity(self, def_id: impl IntoQueryParam<DefId>) -> ty::ImplPolarity {
-        self.impl_trait_header(def_id)
-            .map_or(ty::ImplPolarity::Positive, |h| h.skip_binder().polarity)
+        self.impl_trait_header(def_id).map_or(ty::ImplPolarity::Positive, |h| h.polarity)
     }
 }
 

compiler/rustc_middle/src/ty/mod.rs

@@ -250,9 +250,9 @@ pub struct ImplHeader<'tcx> {
     pub predicates: Vec<Predicate<'tcx>>,
 }
 
-#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, TyEncodable, TyDecodable, HashStable)]
+#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub struct ImplTraitHeader<'tcx> {
-    pub trait_ref: ty::TraitRef<'tcx>,
+    pub trait_ref: ty::EarlyBinder<ty::TraitRef<'tcx>>,
     pub polarity: ImplPolarity,
     pub unsafety: hir::Unsafety,
 }
@@ -1624,12 +1624,15 @@ impl<'tcx> TyCtxt<'tcx> {
         def_id1: DefId,
         def_id2: DefId,
     ) -> Option<ImplOverlapKind> {
-        let impl1 = self.impl_trait_header(def_id1).unwrap().instantiate_identity();
-        let impl2 = self.impl_trait_header(def_id2).unwrap().instantiate_identity();
+        let impl1 = self.impl_trait_header(def_id1).unwrap();
+        let impl2 = self.impl_trait_header(def_id2).unwrap();
+
+        let trait_ref1 = impl1.trait_ref.skip_binder();
+        let trait_ref2 = impl2.trait_ref.skip_binder();
 
         // If either trait impl references an error, they're allowed to overlap,
         // as one of them essentially doesn't exist.
-        if impl1.references_error() || impl2.references_error() {
+        if trait_ref1.references_error() || trait_ref2.references_error() {
             return Some(ImplOverlapKind::Permitted { marker: false });
         }
 
@@ -1650,7 +1653,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let is_marker_overlap = {
             let is_marker_impl =
                 |trait_ref: TraitRef<'_>| -> bool { self.trait_def(trait_ref.def_id).is_marker };
-            is_marker_impl(impl1.trait_ref) && is_marker_impl(impl2.trait_ref)
+            is_marker_impl(trait_ref1) && is_marker_impl(trait_ref2)
         };
 
         if is_marker_overlap {

compiler/rustc_monomorphize/src/collector.rs

@@ -1361,7 +1361,7 @@ fn create_mono_items_for_default_impls<'tcx>(
         return;
     };
 
-    if matches!(impl_.skip_binder().polarity, ty::ImplPolarity::Negative) {
+    if matches!(impl_.polarity, ty::ImplPolarity::Negative) {
         return;
     }
 
@@ -1385,7 +1385,7 @@ fn create_mono_items_for_default_impls<'tcx>(
         }
     };
     let impl_args = GenericArgs::for_item(tcx, item.owner_id.to_def_id(), only_region_params);
-    let trait_ref = impl_.instantiate(tcx, impl_args).trait_ref;
+    let trait_ref = impl_.trait_ref.instantiate(tcx, impl_args);
 
     // Unlike 'lazy' monomorphization that begins by collecting items transitively
     // called by `main` or other global items, when eagerly monomorphizing impl

compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs

@@ -166,13 +166,13 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
         let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
         if !drcx.args_may_unify(
             goal.predicate.trait_ref(tcx).args,
-            impl_trait_header.skip_binder().trait_ref.args,
+            impl_trait_header.trait_ref.skip_binder().args,
         ) {
             return Err(NoSolution);
         }
 
         // We have to ignore negative impls when projecting.
-        let impl_polarity = impl_trait_header.skip_binder().polarity;
+        let impl_polarity = impl_trait_header.polarity;
         match impl_polarity {
             ty::ImplPolarity::Negative => return Err(NoSolution),
             ty::ImplPolarity::Reservation => {
@@ -183,7 +183,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
 
         ecx.probe_trait_candidate(CandidateSource::Impl(impl_def_id)).enter(|ecx| {
             let impl_args = ecx.fresh_args_for_item(impl_def_id);
-            let impl_trait_ref = impl_trait_header.instantiate(tcx, impl_args).trait_ref;
+            let impl_trait_ref = impl_trait_header.trait_ref.instantiate(tcx, impl_args);
 
             ecx.eq(goal.param_env, goal_trait_ref, impl_trait_ref)?;