Auto merge of #106696 - kylematsuda:early-binder, r=lcnr

Switch to `EarlyBinder` for `const_param_default` and `impl_trait_ref` queries

Part of the work to close #105779 and implement https://github.com/rust-lang/types-team/issues/78.

Several queries `X` have a `bound_X` variant that wraps the output in `EarlyBinder`. This PR adds `EarlyBinder` to the return type of  `const_param_default` and `impl_trait_ref`, and removes their `bound_X` variants.

r? `@lcnr`

12 files changed, 38 insertions, 32 deletions

diff --git a/compiler/rustc_hir_analysis/src/astconv/mod.rs b/compiler/rustc_hir_analysis/src/astconv/mod.rs
index 3521911b055..8d2cc70c05f 100644
--- a/compiler/rustc_hir_analysis/src/astconv/mod.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/mod.rs
@@ -511,9 +511,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                             return tcx.const_error(ty).into();
                         }
                         if !infer_args && has_default {
-                            tcx.bound_const_param_default(param.def_id)
-                                .subst(tcx, substs.unwrap())
-                                .into()
+                            tcx.const_param_default(param.def_id).subst(tcx, substs.unwrap()).into()
                         } else {
                             if infer_args {
                                 self.astconv.ct_infer(ty, Some(param), self.span).into()
@@ -2068,7 +2066,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 };
 
                 self.one_bound_for_assoc_type(
-                    || traits::supertraits(tcx, ty::Binder::dummy(trait_ref)),
+                    || traits::supertraits(tcx, ty::Binder::dummy(trait_ref.subst_identity())),
                     || "Self".to_string(),
                     assoc_ident,
                     span,
@@ -2157,7 +2155,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                 .is_accessible_from(self.item_def_id(), tcx)
                             && tcx.all_impls(*trait_def_id)
                                 .any(|impl_def_id| {
-                                    let trait_ref = tcx.bound_impl_trait_ref(impl_def_id);
+                                    let trait_ref = tcx.impl_trait_ref(impl_def_id);
                                     trait_ref.map_or(false, |trait_ref| {
                                         let impl_ = trait_ref.subst(
                                             tcx,
@@ -2310,7 +2308,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                             && tcx.impl_polarity(impl_def_id) != ty::ImplPolarity::Negative
                     })
                     .filter_map(|impl_def_id| tcx.impl_trait_ref(impl_def_id))
-                    .map(|impl_| impl_.self_ty())
+                    .map(|impl_| impl_.subst_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())
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 43795cfba3f..e58669433e2 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -540,7 +540,7 @@ fn check_item_type(tcx: TyCtxt<'_>, id: hir::ItemId) {
                     tcx,
                     it.span,
                     it.owner_id.def_id,
-                    impl_trait_ref,
+                    impl_trait_ref.subst_identity(),
                     &impl_.items,
                 );
                 check_on_unimplemented(tcx, it);
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 2cdf7579471..770d7b6f927 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -616,7 +616,8 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
 ) -> Result<&'tcx FxHashMap<DefId, Ty<'tcx>>, ErrorGuaranteed> {
     let impl_m = tcx.opt_associated_item(def_id).unwrap();
     let trait_m = tcx.opt_associated_item(impl_m.trait_item_def_id.unwrap()).unwrap();
-    let impl_trait_ref = tcx.impl_trait_ref(impl_m.impl_container(tcx).unwrap()).unwrap();
+    let impl_trait_ref =
+        tcx.impl_trait_ref(impl_m.impl_container(tcx).unwrap()).unwrap().subst_identity();
     let param_env = tcx.param_env(def_id);
 
     // First, check a few of the same things as `compare_impl_method`,
@@ -1684,7 +1685,8 @@ pub(super) fn compare_impl_const_raw(
 ) -> Result<(), ErrorGuaranteed> {
     let impl_const_item = tcx.associated_item(impl_const_item_def);
     let trait_const_item = tcx.associated_item(trait_const_item_def);
-    let impl_trait_ref = tcx.impl_trait_ref(impl_const_item.container_id(tcx)).unwrap();
+    let impl_trait_ref =
+        tcx.impl_trait_ref(impl_const_item.container_id(tcx)).unwrap().subst_identity();
     debug!("compare_const_impl(impl_trait_ref={:?})", impl_trait_ref);
 
     let impl_c_span = tcx.def_span(impl_const_item_def.to_def_id());
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index 92fd4625ee8..912e0ec560b 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -182,7 +182,7 @@ fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
         hir::ItemKind::Impl(ref impl_) => {
             let is_auto = tcx
                 .impl_trait_ref(def_id)
-                .map_or(false, |trait_ref| tcx.trait_is_auto(trait_ref.def_id));
+                .map_or(false, |trait_ref| tcx.trait_is_auto(trait_ref.skip_binder().def_id));
             if let (hir::Defaultness::Default { .. }, true) = (impl_.defaultness, is_auto) {
                 let sp = impl_.of_trait.as_ref().map_or(item.span, |t| t.path.span);
                 let mut err =
@@ -1253,7 +1253,7 @@ fn check_impl<'tcx>(
                 // `#[rustc_reservation_impl]` impls are not real impls and
                 // therefore don't need to be WF (the trait's `Self: Trait` predicate
                 // won't hold).
-                let trait_ref = tcx.impl_trait_ref(item.owner_id).unwrap();
+                let trait_ref = tcx.impl_trait_ref(item.owner_id).unwrap().subst_identity();
                 let trait_ref = wfcx.normalize(
                     ast_trait_ref.path.span,
                     Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),
@@ -1350,7 +1350,7 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
                     // is incorrect when dealing with unused substs, for example
                     // for `struct Foo<const N: usize, const M: usize = { 1 - 2 }>`
                     // we should eagerly error.
-                    let default_ct = tcx.const_param_default(param.def_id);
+                    let default_ct = tcx.const_param_default(param.def_id).subst_identity();
                     if !default_ct.needs_subst() {
                         wfcx.register_wf_obligation(
                             tcx.def_span(param.def_id),
@@ -1396,7 +1396,7 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
             GenericParamDefKind::Const { .. } => {
                 // If the param has a default, ...
                 if is_our_default(param) {
-                    let default_ct = tcx.const_param_default(param.def_id);
+                    let default_ct = tcx.const_param_default(param.def_id).subst_identity();
                     // ... and it's not a dependent default, ...
                     if !default_ct.needs_subst() {
                         // ... then substitute it with the default.
diff --git a/compiler/rustc_hir_analysis/src/coherence/builtin.rs b/compiler/rustc_hir_analysis/src/coherence/builtin.rs
index 2e2c1591e9b..5bdd18fcd63 100644
--- a/compiler/rustc_hir_analysis/src/coherence/builtin.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/builtin.rs
@@ -192,7 +192,7 @@ fn visit_implementation_of_dispatch_from_dyn(tcx: TyCtxt<'_>, impl_did: LocalDef
     let source = tcx.type_of(impl_did);
     assert!(!source.has_escaping_bound_vars());
     let target = {
-        let trait_ref = tcx.impl_trait_ref(impl_did).unwrap();
+        let trait_ref = tcx.impl_trait_ref(impl_did).unwrap().subst_identity();
         assert_eq!(trait_ref.def_id, dispatch_from_dyn_trait);
 
         trait_ref.substs.type_at(1)
@@ -354,7 +354,7 @@ pub fn coerce_unsized_info<'tcx>(tcx: TyCtxt<'tcx>, impl_did: DefId) -> CoerceUn
     });
 
     let source = tcx.type_of(impl_did);
-    let trait_ref = tcx.impl_trait_ref(impl_did).unwrap();
+    let trait_ref = tcx.impl_trait_ref(impl_did).unwrap().subst_identity();
     assert_eq!(trait_ref.def_id, coerce_unsized_trait);
     let target = trait_ref.substs.type_at(1);
     debug!("visit_implementation_of_coerce_unsized: {:?} -> {:?} (bound)", source, target);
diff --git a/compiler/rustc_hir_analysis/src/coherence/mod.rs b/compiler/rustc_hir_analysis/src/coherence/mod.rs
index 1bf3768fead..2e9cd2fca01 100644
--- a/compiler/rustc_hir_analysis/src/coherence/mod.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/mod.rs
@@ -128,7 +128,7 @@ fn coherent_trait(tcx: TyCtxt<'_>, def_id: DefId) {
 
     let impls = tcx.hir().trait_impls(def_id);
     for &impl_def_id in impls {
-        let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
+        let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().subst_identity();
 
         check_impl(tcx, impl_def_id, trait_ref);
         check_object_overlap(tcx, impl_def_id, trait_ref);
diff --git a/compiler/rustc_hir_analysis/src/coherence/orphan.rs b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
index e8b3f139623..0aadc9f311b 100644
--- a/compiler/rustc_hir_analysis/src/coherence/orphan.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
@@ -21,7 +21,7 @@ pub(crate) fn orphan_check_impl(
     tcx: TyCtxt<'_>,
     impl_def_id: LocalDefId,
 ) -> Result<(), ErrorGuaranteed> {
-    let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
+    let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().subst_identity();
     trait_ref.error_reported()?;
 
     let ret = do_orphan_check_impl(tcx, trait_ref, impl_def_id);
diff --git a/compiler/rustc_hir_analysis/src/coherence/unsafety.rs b/compiler/rustc_hir_analysis/src/coherence/unsafety.rs
index 70cc15b2f8c..a485768e37b 100644
--- a/compiler/rustc_hir_analysis/src/coherence/unsafety.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/unsafety.rs
@@ -14,6 +14,7 @@ pub(super) fn check_item(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     let hir::ItemKind::Impl(ref impl_) = item.kind else { bug!() };
 
     if let Some(trait_ref) = tcx.impl_trait_ref(item.owner_id) {
+        let trait_ref = trait_ref.subst_identity();
         let trait_def = tcx.trait_def(trait_ref.def_id);
         let unsafe_attr =
             impl_.generics.params.iter().find(|p| p.pure_wrt_drop).map(|_| "may_dangle");
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index cd745ee8cab..35f47dfc1a5 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -1339,18 +1339,22 @@ fn suggest_impl_trait<'tcx>(
     None
 }
 
-fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
+fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::EarlyBinder<ty::TraitRef<'_>>> {
     let icx = ItemCtxt::new(tcx, def_id);
     let item = tcx.hir().expect_item(def_id.expect_local());
     match item.kind {
-        hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
-            let selfty = tcx.type_of(def_id);
-            icx.astconv().instantiate_mono_trait_ref(
-                ast_trait_ref,
-                selfty,
-                check_impl_constness(tcx, impl_.constness, ast_trait_ref),
-            )
-        }),
+        hir::ItemKind::Impl(ref impl_) => impl_
+            .of_trait
+            .as_ref()
+            .map(|ast_trait_ref| {
+                let selfty = tcx.type_of(def_id);
+                icx.astconv().instantiate_mono_trait_ref(
+                    ast_trait_ref,
+                    selfty,
+                    check_impl_constness(tcx, impl_.constness, ast_trait_ref),
+                )
+            })
+            .map(ty::EarlyBinder),
         _ => bug!(),
     }
 }
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index 23425355684..a7e6494c15a 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -87,7 +87,8 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
         Node::Item(item) => match item.kind {
             ItemKind::Impl(ref impl_) => {
                 if impl_.defaultness.is_default() {
-                    is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
+                    is_default_impl_trait =
+                        tcx.impl_trait_ref(def_id).map(|t| ty::Binder::dummy(t.subst_identity()));
                 }
                 &impl_.generics
             }
@@ -251,7 +252,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
     // for details.
     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
         let self_ty = tcx.type_of(def_id);
-        let trait_ref = tcx.impl_trait_ref(def_id);
+        let trait_ref = tcx.impl_trait_ref(def_id).map(ty::EarlyBinder::subst_identity);
         cgp::setup_constraining_predicates(
             tcx,
             &mut predicates,
diff --git a/compiler/rustc_hir_analysis/src/impl_wf_check.rs b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
index 136f6199911..4fe893442b9 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
@@ -85,7 +85,7 @@ fn enforce_impl_params_are_constrained(tcx: TyCtxt<'_>, impl_def_id: LocalDefId)
     }
     let impl_generics = tcx.generics_of(impl_def_id);
     let impl_predicates = tcx.predicates_of(impl_def_id);
-    let impl_trait_ref = tcx.impl_trait_ref(impl_def_id);
+    let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).map(ty::EarlyBinder::subst_identity);
 
     let mut input_parameters = cgp::parameters_for_impl(impl_self_ty, impl_trait_ref);
     cgp::identify_constrained_generic_params(
diff --git a/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs b/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
index 8b9034d9620..bcda26c4cc8 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
@@ -90,7 +90,7 @@ pub(super) fn check_min_specialization(tcx: TyCtxt<'_>, impl_def_id: LocalDefId)
 
 fn parent_specialization_node(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId) -> Option<Node> {
     let trait_ref = tcx.impl_trait_ref(impl1_def_id)?;
-    let trait_def = tcx.trait_def(trait_ref.def_id);
+    let trait_def = tcx.trait_def(trait_ref.skip_binder().def_id);
 
     let impl2_node = trait_def.ancestors(tcx, impl1_def_id.to_def_id()).ok()?.nth(1)?;
 
@@ -207,7 +207,7 @@ fn unconstrained_parent_impl_substs<'tcx>(
     let impl_generic_predicates = tcx.predicates_of(impl_def_id);
     let mut unconstrained_parameters = FxHashSet::default();
     let mut constrained_params = FxHashSet::default();
-    let impl_trait_ref = tcx.impl_trait_ref(impl_def_id);
+    let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).map(ty::EarlyBinder::subst_identity);
 
     // Unfortunately the functions in `constrained_generic_parameters` don't do
     // what we want here. We want only a list of constrained parameters while
@@ -370,7 +370,7 @@ fn check_predicates<'tcx>(
     });
 
     // Include the well-formed predicates of the type parameters of the impl.
-    for arg in tcx.impl_trait_ref(impl1_def_id).unwrap().substs {
+    for arg in tcx.impl_trait_ref(impl1_def_id).unwrap().subst_identity().substs {
         let infcx = &tcx.infer_ctxt().build();
         let obligations = wf::obligations(
             infcx,