Don't opt_rpitit_info as a separate query

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -1338,6 +1338,7 @@ impl<'tcx> Pick<'tcx> {
                     container: _,
                     trait_item_def_id: _,
                     fn_has_self_parameter: _,
+                    opt_rpitit_info: _,
                 },
             kind: _,
             import_ids: _,

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1096,6 +1096,8 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             trait_item_def_id: self.get_trait_item_def_id(id),
             container,
             fn_has_self_parameter: has_self,
+            // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): We need to encode this
+            opt_rpitit_info: None,
         }
     }
 

compiler/rustc_middle/src/hir/mod.rs

@@ -177,7 +177,6 @@ pub fn provide(providers: &mut Providers) {
         }
     };
     providers.opt_def_kind = |tcx, def_id| tcx.hir().opt_def_kind(def_id.expect_local());
-    providers.opt_rpitit_info = |_, _| None;
     providers.all_local_trait_impls = |tcx, ()| &tcx.resolutions(()).trait_impls;
     providers.expn_that_defined = |tcx, id| {
         let id = id.expect_local();

compiler/rustc_middle/src/query/mod.rs

@@ -1161,14 +1161,6 @@ rustc_queries! {
         feedable
     }
 
-    /// The `opt_rpitit_info` query returns the pair of the def id of the function where the RPIT
-    /// is defined and the opaque def id if any.
-    query opt_rpitit_info(def_id: DefId) -> Option<ty::ImplTraitInTraitData> {
-        desc { |tcx| "opt_rpitit_info `{}`", tcx.def_path_str(def_id) }
-        cache_on_disk_if { def_id.is_local() }
-        feedable
-    }
-
     /// Gets the span for the definition.
     query def_span(def_id: DefId) -> Span {
         desc { |tcx| "looking up span for `{}`", tcx.def_path_str(def_id) }

compiler/rustc_middle/src/ty/assoc.rs

@@ -30,6 +30,11 @@ pub struct AssocItem {
     /// Whether this is a method with an explicit self
     /// as its first parameter, allowing method calls.
     pub fn_has_self_parameter: bool,
+
+    /// `Some` if the associated item (an associated type) comes from the
+    /// return-position `impl Trait` in trait desugaring. The `ImplTraitInTraitData`
+    /// provides additional information about its source.
+    pub opt_rpitit_info: Option<ty::ImplTraitInTraitData>,
 }
 
 impl AssocItem {

compiler/rustc_middle/src/ty/context.rs

@@ -2452,7 +2452,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
     pub fn is_impl_trait_in_trait(self, def_id: DefId) -> bool {
         if self.lower_impl_trait_in_trait_to_assoc_ty() {
-            self.def_kind(def_id) == DefKind::AssocTy && self.opt_rpitit_info(def_id).is_some()
+            self.opt_rpitit_info(def_id).is_some()
         } else {
             self.def_kind(def_id) == DefKind::ImplTraitPlaceholder
         }

compiler/rustc_middle/src/ty/mod.rs

@@ -2070,7 +2070,9 @@ pub enum ImplOverlapKind {
     Issue33140,
 }
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
+/// Useful source information about where a desugared associated type for an
+/// RPITIT originated from.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Encodable, Decodable, HashStable)]
 pub enum ImplTraitInTraitData {
     Trait { fn_def_id: DefId, opaque_def_id: DefId },
     Impl { fn_def_id: DefId },
@@ -2213,6 +2215,17 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
+    /// If the def-id is an associated type that was desugared from a
+    /// return-position `impl Trait` from a trait, then provide the source info
+    /// about where that RPITIT came from.
+    pub fn opt_rpitit_info(self, def_id: DefId) -> Option<ImplTraitInTraitData> {
+        if let DefKind::AssocTy = self.def_kind(def_id) {
+            self.associated_item(def_id).opt_rpitit_info
+        } else {
+            None
+        }
+    }
+
     pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> {
         variant
             .fields

compiler/rustc_passes/src/dead.rs

@@ -244,7 +244,7 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
             }
 
             // Avoid accessing the HIR for the synthesized associated type generated for RPITITs.
-            if self.tcx.opt_rpitit_info(id).is_some() {
+            if self.tcx.opt_rpitit_info(id.to_def_id()).is_some() {
                 self.live_symbols.insert(id);
                 continue;
             }

compiler/rustc_ty_utils/src/assoc.rs

@@ -153,6 +153,7 @@ fn associated_item_from_trait_item_ref(trait_item_ref: &hir::TraitItemRef) -> ty
         trait_item_def_id: Some(owner_id.to_def_id()),
         container: ty::TraitContainer,
         fn_has_self_parameter: has_self,
+        opt_rpitit_info: None,
     }
 }
 
@@ -171,6 +172,7 @@ fn associated_item_from_impl_item_ref(impl_item_ref: &hir::ImplItemRef) -> ty::A
         trait_item_def_id: impl_item_ref.trait_item_def_id,
         container: ty::ImplContainer,
         fn_has_self_parameter: has_self,
+        opt_rpitit_info: None,
     }
 }
 
@@ -262,12 +264,6 @@ fn associated_item_for_impl_trait_in_trait(
     // Copy span of the opaque.
     trait_assoc_ty.def_ident_span(Some(span));
 
-    // Add the def_id of the function and opaque that generated this synthesized associated type.
-    trait_assoc_ty.opt_rpitit_info(Some(ImplTraitInTraitData::Trait {
-        fn_def_id,
-        opaque_def_id: opaque_ty_def_id.to_def_id(),
-    }));
-
     trait_assoc_ty.associated_item(ty::AssocItem {
         name: kw::Empty,
         kind: ty::AssocKind::Type,
@@ -275,6 +271,10 @@ fn associated_item_for_impl_trait_in_trait(
         trait_item_def_id: None,
         container: ty::TraitContainer,
         fn_has_self_parameter: false,
+        opt_rpitit_info: Some(ImplTraitInTraitData::Trait {
+            fn_def_id,
+            opaque_def_id: opaque_ty_def_id.to_def_id(),
+        }),
     });
 
     // Copy visility of the containing function.
@@ -328,11 +328,6 @@ fn impl_associated_item_for_impl_trait_in_trait(
     // `opt_local_def_id_to_hir_id` with `None`.
     impl_assoc_ty.opt_local_def_id_to_hir_id(None);
 
-    // Add the def_id of the function that generated this synthesized associated type.
-    impl_assoc_ty.opt_rpitit_info(Some(ImplTraitInTraitData::Impl {
-        fn_def_id: impl_fn_def_id.to_def_id(),
-    }));
-
     impl_assoc_ty.associated_item(ty::AssocItem {
         name: kw::Empty,
         kind: ty::AssocKind::Type,
@@ -340,6 +335,7 @@ fn impl_associated_item_for_impl_trait_in_trait(
         trait_item_def_id: Some(trait_assoc_def_id.to_def_id()),
         container: ty::ImplContainer,
         fn_has_self_parameter: false,
+        opt_rpitit_info: Some(ImplTraitInTraitData::Impl { fn_def_id: impl_fn_def_id.to_def_id() }),
     });
 
     // Copy param_env of the containing function. The synthesized associated type doesn't have