Fix generics_of on traits new RPITITs and also migrate from ImplTraitPlaceholder to is_impl_trait_in_trait

compiler/rustc_hir_analysis/src/check/check.rs

@@ -557,7 +557,7 @@ fn check_item_type(tcx: TyCtxt<'_>, id: hir::ItemId) {
             check_opaque(tcx, id);
         }
         DefKind::ImplTraitPlaceholder => {
-            let parent = tcx.impl_trait_in_trait_parent(id.owner_id.to_def_id());
+            let parent = tcx.impl_trait_in_trait_parent_fn(id.owner_id.to_def_id());
             // Only check the validity of this opaque type if the function has a default body
             if let hir::Node::TraitItem(hir::TraitItem {
                 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1,7 +1,6 @@
 use crate::autoderef::Autoderef;
 use crate::constrained_generic_params::{identify_constrained_generic_params, Parameter};
 
-use hir::def::DefKind;
 use rustc_ast as ast;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
@@ -1549,8 +1548,13 @@ fn check_return_position_impl_trait_in_trait_bounds<'tcx>(
         for arg in fn_output.walk() {
             if let ty::GenericArgKind::Type(ty) = arg.unpack()
                 && let ty::Alias(ty::Opaque, proj) = ty.kind()
-                && tcx.def_kind(proj.def_id) == DefKind::ImplTraitPlaceholder
-                && tcx.impl_trait_in_trait_parent(proj.def_id) == fn_def_id.to_def_id()
+                // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty) we should just check
+                // `tcx.def_kind(proj.def_id) == DefKind::ImplTraitPlaceholder`. Right now
+                // `check_associated_type_bounds` is not called for RPITITs synthesized as
+                // associated types. See `check_mod_type_wf` to see how synthesized associated
+                // types are missed due to iterating over HIR.
+                && tcx.is_impl_trait_in_trait(proj.def_id)
+                && tcx.impl_trait_in_trait_parent_fn(proj.def_id) == fn_def_id.to_def_id()
             {
                 let span = tcx.def_span(proj.def_id);
                 let bounds = wfcx.tcx().explicit_item_bounds(proj.def_id);

compiler/rustc_hir_analysis/src/variance/mod.rs

@@ -112,10 +112,14 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
         fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
             match t.kind() {
                 ty::Alias(_, ty::AliasTy { def_id, substs, .. })
-                    if matches!(
-                        self.tcx.def_kind(*def_id),
-                        DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder
-                    ) =>
+                    if matches!(self.tcx.def_kind(*def_id), DefKind::OpaqueTy) =>
+                {
+                    self.visit_opaque(*def_id, substs)
+                }
+                // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty) check whether this is necessary
+                // at all for RPITITs.
+                ty::Alias(_, ty::AliasTy { def_id, substs, .. })
+                    if self.tcx.is_impl_trait_in_trait(*def_id) =>
                 {
                     self.visit_opaque(*def_id, substs)
                 }

compiler/rustc_hir_typeck/src/closure.rs

@@ -2,7 +2,6 @@
 
 use super::{check_fn, Expectation, FnCtxt, GeneratorTypes};
 
-use hir::def::DefKind;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::lang_items::LangItem;
@@ -713,14 +712,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .subst_iter_copied(self.tcx, substs)
                 .find_map(|(p, s)| get_future_output(p, s))?,
             ty::Error(_) => return None,
-            ty::Alias(ty::Projection, proj)
-                if self.tcx.def_kind(proj.def_id) == DefKind::ImplTraitPlaceholder =>
-            {
-                self.tcx
-                    .bound_explicit_item_bounds(proj.def_id)
-                    .subst_iter_copied(self.tcx, proj.substs)
-                    .find_map(|(p, s)| get_future_output(p, s))?
-            }
+            ty::Alias(ty::Projection, proj) if self.tcx.is_impl_trait_in_trait(proj.def_id) => self
+                .tcx
+                .bound_explicit_item_bounds(proj.def_id)
+                .subst_iter_copied(self.tcx, proj.substs)
+                .find_map(|(p, s)| get_future_output(p, s))?,
             _ => span_bug!(
                 self.tcx.def_span(expr_def_id),
                 "async fn generator return type not an inference variable: {ret_ty}"

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -359,10 +359,12 @@ impl<'tcx> InferCtxt<'tcx> {
     pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
         let (def_id, substs) = match *ty.kind() {
             ty::Alias(_, ty::AliasTy { def_id, substs, .. })
-                if matches!(
-                    self.tcx.def_kind(def_id),
-                    DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder
-                ) =>
+                if matches!(self.tcx.def_kind(def_id), DefKind::OpaqueTy) =>
+            {
+                (def_id, substs)
+            }
+            ty::Alias(_, ty::AliasTy { def_id, substs, .. })
+                if self.tcx.is_impl_trait_in_trait(def_id) =>
             {
                 (def_id, substs)
             }
@@ -1754,8 +1756,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                                 )
                             }
                             (true, ty::Alias(ty::Projection, proj))
-                                if self.tcx.def_kind(proj.def_id)
-                                    == DefKind::ImplTraitPlaceholder =>
+                                if self.tcx.is_impl_trait_in_trait(proj.def_id) =>
                             {
                                 let sm = self.tcx.sess.source_map();
                                 let pos = sm.lookup_char_pos(self.tcx.def_span(proj.def_id).lo());

compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs

@@ -1,7 +1,7 @@
 use super::TypeErrCtxt;
 use rustc_errors::Applicability::{MachineApplicable, MaybeIncorrect};
 use rustc_errors::{pluralize, Diagnostic, MultiSpan};
-use rustc_hir::{self as hir, def::DefKind};
+use rustc_hir as hir;
 use rustc_middle::traits::ObligationCauseCode;
 use rustc_middle::ty::error::ExpectedFound;
 use rustc_middle::ty::print::Printer;
@@ -75,7 +75,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         diag.note("an associated type was expected, but a different one was found");
                     }
                     (ty::Param(p), ty::Alias(ty::Projection, proj)) | (ty::Alias(ty::Projection, proj), ty::Param(p))
-                        if tcx.def_kind(proj.def_id) != DefKind::ImplTraitPlaceholder =>
+                        if !tcx.is_impl_trait_in_trait(proj.def_id) =>
                     {
                         let p_def_id = tcx
                             .generics_of(body_owner_def_id)
@@ -222,7 +222,7 @@ impl<T> Trait<T> for X {
                             diag.span_label(p_span, "this type parameter");
                         }
                     }
-                    (ty::Alias(ty::Projection, proj_ty), _) if tcx.def_kind(proj_ty.def_id) != DefKind::ImplTraitPlaceholder => {
+                    (ty::Alias(ty::Projection, proj_ty), _) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => {
                         self.expected_projection(
                             diag,
                             proj_ty,
@@ -231,7 +231,7 @@ impl<T> Trait<T> for X {
                             cause.code(),
                         );
                     }
-                    (_, ty::Alias(ty::Projection, proj_ty)) if tcx.def_kind(proj_ty.def_id) != DefKind::ImplTraitPlaceholder => {
+                    (_, ty::Alias(ty::Projection, proj_ty)) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => {
                         let msg = format!(
                             "consider constraining the associated type `{}` to `{}`",
                             values.found, values.expected,

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -1,7 +1,6 @@
 use crate::errors::OpaqueHiddenTypeDiag;
 use crate::infer::{DefiningAnchor, InferCtxt, InferOk};
 use crate::traits;
-use hir::def::DefKind;
 use hir::def_id::{DefId, LocalDefId};
 use hir::OpaqueTyOrigin;
 use rustc_data_structures::sync::Lrc;
@@ -481,9 +480,7 @@ where
                 }
             }
 
-            ty::Alias(ty::Projection, proj)
-                if self.tcx.def_kind(proj.def_id) == DefKind::ImplTraitPlaceholder =>
-            {
+            ty::Alias(ty::Projection, proj) if self.tcx.is_impl_trait_in_trait(proj.def_id) => {
                 // Skip lifetime parameters that are not captures.
                 let variances = self.tcx.variances_of(proj.def_id);
 
@@ -563,8 +560,7 @@ impl<'tcx> InferCtxt<'tcx> {
                     // FIXME(RPITIT): Don't replace RPITITs with inference vars.
                     ty::Alias(ty::Projection, projection_ty)
                         if !projection_ty.has_escaping_bound_vars()
-                            && tcx.def_kind(projection_ty.def_id)
-                                != DefKind::ImplTraitPlaceholder =>
+                            && !tcx.is_impl_trait_in_trait(projection_ty.def_id) =>
                     {
                         self.infer_projection(
                             param_env,

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1028,7 +1028,7 @@ fn should_encode_type(tcx: TyCtxt<'_>, def_id: LocalDefId, def_kind: DefKind) ->
         | DefKind::InlineConst => true,
 
         DefKind::ImplTraitPlaceholder => {
-            let parent_def_id = tcx.impl_trait_in_trait_parent(def_id.to_def_id());
+            let parent_def_id = tcx.impl_trait_in_trait_parent_fn(def_id.to_def_id());
             let assoc_item = tcx.associated_item(parent_def_id);
             match assoc_item.container {
                 // Always encode an RPIT in an impl fn, since it always has a body

compiler/rustc_middle/src/query/mod.rs

@@ -191,6 +191,7 @@ rustc_queries! {
     {
         desc { "determine whether the opaque is a type-alias impl trait" }
         separate_provide_extern
+        feedable
     }
 
     query unsizing_params_for_adt(key: DefId) -> &'tcx rustc_index::bit_set::BitSet<u32>

compiler/rustc_middle/src/ty/mod.rs

@@ -2552,12 +2552,18 @@ impl<'tcx> TyCtxt<'tcx> {
         matches!(self.trait_of_item(def_id), Some(trait_id) if self.has_attr(trait_id, sym::const_trait))
     }
 
-    pub fn impl_trait_in_trait_parent(self, mut def_id: DefId) -> DefId {
-        while let def_kind = self.def_kind(def_id) && def_kind != DefKind::AssocFn {
-            debug_assert_eq!(def_kind, DefKind::ImplTraitPlaceholder);
-            def_id = self.parent(def_id);
+    pub fn impl_trait_in_trait_parent_fn(self, mut def_id: DefId) -> DefId {
+        match self.opt_rpitit_info(def_id) {
+            Some(ImplTraitInTraitData::Trait { fn_def_id, .. })
+            | Some(ImplTraitInTraitData::Impl { fn_def_id, .. }) => fn_def_id,
+            None => {
+                while let def_kind = self.def_kind(def_id) && def_kind != DefKind::AssocFn {
+                    debug_assert_eq!(def_kind, DefKind::ImplTraitPlaceholder);
+                    def_id = self.parent(def_id);
+                }
+                def_id
+            }
         }
-        def_id
     }
 
     pub fn impl_method_has_trait_impl_trait_tys(self, def_id: DefId) -> bool {
@@ -2572,6 +2578,10 @@ impl<'tcx> TyCtxt<'tcx> {
 
         let Some(trait_item_def_id) = item.trait_item_def_id else { return false; };
 
+        if self.lower_impl_trait_in_trait_to_assoc_ty() {
+            return !self.associated_items_for_impl_trait_in_trait(trait_item_def_id).is_empty();
+        }
+
         // FIXME(RPITIT): This does a somewhat manual walk through the signature
         // of the trait fn to look for any RPITITs, but that's kinda doing a lot
         // of work. We can probably remove this when we refactor RPITITs to be

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -728,7 +728,7 @@ pub trait PrettyPrinter<'tcx>:
             }
             ty::Alias(ty::Projection, ref data) => {
                 if !(self.should_print_verbose() || NO_QUERIES.with(|q| q.get()))
-                    && self.tcx().def_kind(data.def_id) == DefKind::ImplTraitPlaceholder
+                    && self.tcx().is_impl_trait_in_trait(data.def_id)
                 {
                     return self.pretty_print_opaque_impl_type(data.def_id, data.substs);
                 } else {

compiler/rustc_middle/src/ty/sty.rs

@@ -1288,7 +1288,7 @@ impl<'tcx> AliasTy<'tcx> {
         match tcx.def_kind(self.def_id) {
             DefKind::AssocTy | DefKind::AssocConst => tcx.parent(self.def_id),
             DefKind::ImplTraitPlaceholder => {
-                tcx.parent(tcx.impl_trait_in_trait_parent(self.def_id))
+                tcx.parent(tcx.impl_trait_in_trait_parent_fn(self.def_id))
             }
             kind => bug!("expected a projection AliasTy; found {kind:?}"),
         }

compiler/rustc_privacy/src/lib.rs

@@ -132,7 +132,7 @@ where
                 projection.trait_ref_and_own_substs(tcx)
             } else {
                 // HACK(RPITIT): Remove this when RPITITs are lowered to regular assoc tys
-                let def_id = tcx.impl_trait_in_trait_parent(projection.def_id);
+                let def_id = tcx.impl_trait_in_trait_parent_fn(projection.def_id);
                 let trait_generics = tcx.generics_of(def_id);
                 (
                     tcx.mk_trait_ref(def_id, projection.substs.truncate_to(tcx, trait_generics)),

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1295,7 +1295,7 @@ fn assemble_candidate_for_impl_trait_in_trait<'cx, 'tcx>(
 ) {
     let tcx = selcx.tcx();
     if tcx.def_kind(obligation.predicate.def_id) == DefKind::ImplTraitPlaceholder {
-        let trait_fn_def_id = tcx.impl_trait_in_trait_parent(obligation.predicate.def_id);
+        let trait_fn_def_id = tcx.impl_trait_in_trait_parent_fn(obligation.predicate.def_id);
 
         let trait_def_id = tcx.parent(trait_fn_def_id);
         let trait_substs =
@@ -2193,7 +2193,7 @@ fn confirm_impl_trait_in_trait_candidate<'tcx>(
     let tcx = selcx.tcx();
     let mut obligations = data.nested;
 
-    let trait_fn_def_id = tcx.impl_trait_in_trait_parent(obligation.predicate.def_id);
+    let trait_fn_def_id = tcx.impl_trait_in_trait_parent_fn(obligation.predicate.def_id);
     let leaf_def = match specialization_graph::assoc_def(tcx, data.impl_def_id, trait_fn_def_id) {
         Ok(assoc_ty) => assoc_ty,
         Err(guar) => return Progress::error(tcx, guar),

compiler/rustc_ty_utils/src/assoc.rs

@@ -244,7 +244,7 @@ fn associated_item_for_impl_trait_in_trait(
     tcx: TyCtxt<'_>,
     opaque_ty_def_id: LocalDefId,
 ) -> LocalDefId {
-    let fn_def_id = tcx.impl_trait_in_trait_parent(opaque_ty_def_id.to_def_id());
+    let fn_def_id = tcx.impl_trait_in_trait_parent_fn(opaque_ty_def_id.to_def_id());
     let trait_def_id = tcx.parent(fn_def_id);
     assert_eq!(tcx.def_kind(trait_def_id), DefKind::Trait);
 
@@ -289,8 +289,39 @@ fn associated_item_for_impl_trait_in_trait(
         InternalSubsts::identity_for_item(tcx, opaque_ty_def_id.to_def_id()),
     )));
 
-    // Copy generics_of of the opaque.
-    trait_assoc_ty.generics_of(tcx.generics_of(opaque_ty_def_id).clone());
+    trait_assoc_ty.is_type_alias_impl_trait(false);
+
+    // Copy generics_of of the opaque type item but the trait is the parent.
+    trait_assoc_ty.generics_of({
+        let opaque_ty_generics = tcx.generics_of(opaque_ty_def_id);
+        let opaque_ty_parent_count = opaque_ty_generics.parent_count;
+        let mut params = opaque_ty_generics.params.clone();
+
+        let parent_generics = tcx.generics_of(trait_def_id);
+        let parent_count = parent_generics.parent_count + parent_generics.params.len();
+
+        let mut trait_fn_params = tcx.generics_of(fn_def_id).params.clone();
+
+        for param in &mut params {
+            param.index = param.index + parent_count as u32 + trait_fn_params.len() as u32
+                - opaque_ty_parent_count as u32;
+        }
+
+        trait_fn_params.extend(params);
+        params = trait_fn_params;
+
+        let param_def_id_to_index =
+            params.iter().map(|param| (param.def_id, param.index)).collect();
+
+        ty::Generics {
+            parent: Some(trait_def_id),
+            parent_count,
+            params,
+            param_def_id_to_index,
+            has_self: false,
+            has_late_bound_regions: opaque_ty_generics.has_late_bound_regions,
+        }
+    });
 
     // There are no predicates for the synthesized associated type.
     trait_assoc_ty.explicit_predicates_of(ty::GenericPredicates {

compiler/rustc_ty_utils/src/ty.rs

@@ -268,8 +268,10 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
 
     fn visit_ty(&mut self, ty: Ty<'tcx>) -> std::ops::ControlFlow<Self::BreakTy> {
         if let ty::Alias(ty::Projection, alias_ty) = *ty.kind()
-            && self.tcx.def_kind(alias_ty.def_id) == DefKind::ImplTraitPlaceholder
-            && self.tcx.impl_trait_in_trait_parent(alias_ty.def_id) == self.fn_def_id
+            // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty) need to project to the opaque, could
+            // get it via type_of + subst.
+            && self.tcx.is_impl_trait_in_trait(alias_ty.def_id)
+            && self.tcx.impl_trait_in_trait_parent_fn(alias_ty.def_id) == self.fn_def_id
             && self.seen.insert(alias_ty.def_id)
         {
             // We have entered some binders as we've walked into the

src/librustdoc/clean/mod.rs

@@ -426,7 +426,7 @@ fn clean_projection<'tcx>(
     cx: &mut DocContext<'tcx>,
     def_id: Option<DefId>,
 ) -> Type {
-    if cx.tcx.def_kind(ty.skip_binder().def_id) == DefKind::ImplTraitPlaceholder {
+    if cx.tcx.is_impl_trait_in_trait(ty.skip_binder().def_id) {
         let bounds = cx
             .tcx
             .explicit_item_bounds(ty.skip_binder().def_id)

tests/ui/async-await/in-trait/async-generics-and-bounds.stderr → tests/ui/async-await/in-trait/async-generics-and-bounds.current.stderr

@@ -1,33 +1,33 @@
 error[E0311]: the parameter type `U` may not live long enough
-  --> $DIR/async-generics-and-bounds.rs:12:28
+  --> $DIR/async-generics-and-bounds.rs:14:28
    |
 LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
    |                            ^^^^^^^
    |
 note: the parameter type `U` must be valid for the anonymous lifetime defined here...
-  --> $DIR/async-generics-and-bounds.rs:12:18
+  --> $DIR/async-generics-and-bounds.rs:14:18
    |
 LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
    |                  ^^^^^
 note: ...so that the reference type `&(T, U)` does not outlive the data it points at
-  --> $DIR/async-generics-and-bounds.rs:12:28
+  --> $DIR/async-generics-and-bounds.rs:14:28
    |
 LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
    |                            ^^^^^^^
 
 error[E0311]: the parameter type `T` may not live long enough
-  --> $DIR/async-generics-and-bounds.rs:12:28
+  --> $DIR/async-generics-and-bounds.rs:14:28
    |
 LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
    |                            ^^^^^^^
    |
 note: the parameter type `T` must be valid for the anonymous lifetime defined here...
-  --> $DIR/async-generics-and-bounds.rs:12:18
+  --> $DIR/async-generics-and-bounds.rs:14:18
    |
 LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
    |                  ^^^^^
 note: ...so that the reference type `&(T, U)` does not outlive the data it points at
-  --> $DIR/async-generics-and-bounds.rs:12:28
+  --> $DIR/async-generics-and-bounds.rs:14:28
    |
 LL |     async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
    |                            ^^^^^^^