Rollup merge of #110299 - kylematsuda:earlybinder-impl-subject, r=compiler-errors

Switch to `EarlyBinder` for `impl_subject` query

Part of the work to finish #105779.

Several queries `X` have a `bound_X` variant that wraps the output in `EarlyBinder`. This adds `EarlyBinder` to the return type of the `impl_subject` query and removes `bound_impl_subject`.

r? `@lcnr`

Author: Dylan-DPC

compiler/rustc_middle/src/hir/mod.rs

@@ -7,7 +7,7 @@ pub mod nested_filter;
 pub mod place;
 
 use crate::ty::query::Providers;
-use crate::ty::{ImplSubject, TyCtxt};
+use crate::ty::{EarlyBinder, ImplSubject, TyCtxt};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::{par_for_each_in, Send, Sync};
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -104,11 +104,11 @@ impl<'tcx> TyCtxt<'tcx> {
         self.parent_module_from_def_id(id.owner.def_id)
     }
 
-    pub fn impl_subject(self, def_id: DefId) -> ImplSubject<'tcx> {
-        self.impl_trait_ref(def_id)
-            .map(|t| t.subst_identity())
-            .map(ImplSubject::Trait)
-            .unwrap_or_else(|| ImplSubject::Inherent(self.type_of(def_id).subst_identity()))
+    pub fn impl_subject(self, def_id: DefId) -> EarlyBinder<ImplSubject<'tcx>> {
+        match self.impl_trait_ref(def_id) {
+            Some(t) => t.map_bound(ImplSubject::Trait),
+            None => self.type_of(def_id).map_bound(ImplSubject::Inherent),
+        }
     }
 }
 

compiler/rustc_middle/src/ty/util.rs

@@ -708,10 +708,6 @@ impl<'tcx> TyCtxt<'tcx> {
         ty::EarlyBinder(self.explicit_item_bounds(def_id))
     }
 
-    pub fn bound_impl_subject(self, def_id: DefId) -> ty::EarlyBinder<ty::ImplSubject<'tcx>> {
-        ty::EarlyBinder(self.impl_subject(def_id))
-    }
-
     /// Returns names of captured upvars for closures and generators.
     ///
     /// Here are some examples:

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -306,7 +306,7 @@ fn negative_impl(tcx: TyCtxt<'_>, impl1_def_id: DefId, impl2_def_id: DefId) -> b
         &infcx,
         ObligationCause::dummy(),
         impl_env,
-        tcx.impl_subject(impl1_def_id),
+        tcx.impl_subject(impl1_def_id).subst_identity(),
     ) {
         Ok(s) => s,
         Err(err) => {

compiler/rustc_trait_selection/src/traits/util.rs

@@ -198,7 +198,7 @@ pub fn impl_subject_and_oblig<'a, 'tcx>(
     impl_def_id: DefId,
     impl_substs: SubstsRef<'tcx>,
 ) -> (ImplSubject<'tcx>, impl Iterator<Item = PredicateObligation<'tcx>>) {
-    let subject = selcx.tcx().bound_impl_subject(impl_def_id);
+    let subject = selcx.tcx().impl_subject(impl_def_id);
     let subject = subject.subst(selcx.tcx(), impl_substs);
 
     let InferOk { value: subject, obligations: normalization_obligations1 } =