Add new rpitit compare mode

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -3049,10 +3049,17 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             }
             &hir::TyKind::OpaqueDef(item_id, lifetimes, in_trait) => {
                 let opaque_ty = tcx.hir().item(item_id);
-                let def_id = item_id.owner_id.to_def_id();
 
                 match opaque_ty.kind {
                     hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
+                        let local_def_id = item_id.owner_id.def_id;
+                        let def_id = if in_trait
+                            && tcx.sess.opts.unstable_opts.lower_impl_trait_in_trait_to_assoc_ty
+                        {
+                            tcx.associated_item_for_impl_trait_in_trait(local_def_id).to_def_id()
+                        } else {
+                            local_def_id.to_def_id()
+                        };
                         self.impl_trait_ty_to_ty(def_id, lifetimes, origin, in_trait)
                     }
                     ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i),

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -831,7 +831,14 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ImplTraitInTraitCollector<'_, 'tcx> {
 
     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
         if let ty::Alias(ty::Projection, proj) = ty.kind()
-            && self.interner().def_kind(proj.def_id) == DefKind::ImplTraitPlaceholder
+            && (self.interner().def_kind(proj.def_id) == DefKind::ImplTraitPlaceholder
+                || self
+                    .interner()
+                    .sess
+                    .opts
+                    .unstable_opts
+                    .lower_impl_trait_in_trait_to_assoc_ty
+                    && self.interner().def_kind(proj.def_id) == DefKind::AssocTy)
         {
             if let Some((ty, _)) = self.types.get(&proj.def_id) {
                 return *ty;
@@ -1996,13 +2003,17 @@ pub(super) fn check_type_bounds<'tcx>(
     let infcx = tcx.infer_ctxt().build();
     let ocx = ObligationCtxt::new(&infcx);
 
-    let impl_ty_span = match tcx.hir().get_by_def_id(impl_ty_def_id) {
-        hir::Node::TraitItem(hir::TraitItem {
-            kind: hir::TraitItemKind::Type(_, Some(ty)),
-            ..
-        }) => ty.span,
-        hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Type(ty), .. }) => ty.span,
-        _ => bug!(),
+    let impl_ty_span = if tcx.opt_rpitit_info(impl_ty_def_id).is_some() {
+        tcx.def_span(impl_ty_def_id)
+    } else {
+        match tcx.hir().get_by_def_id(impl_ty_def_id) {
+            hir::Node::TraitItem(hir::TraitItem {
+                kind: hir::TraitItemKind::Type(_, Some(ty)),
+                ..
+            }) => ty.span,
+            hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Type(ty), .. }) => ty.span,
+            _ => bug!(),
+        }
     };
     let assumed_wf_types = ocx.assumed_wf_types(param_env, impl_ty_span, impl_ty_def_id);
 

compiler/rustc_hir_analysis/src/collect/item_bounds.rs

@@ -3,7 +3,7 @@ use crate::astconv::AstConv;
 use rustc_hir as hir;
 use rustc_infer::traits::util;
 use rustc_middle::ty::subst::InternalSubsts;
-use rustc_middle::ty::{self, DefIdTree, TyCtxt};
+use rustc_middle::ty::{self, DefIdTree, ImplTraitInTraitData, Ty, TyCtxt};
 use rustc_span::def_id::DefId;
 use rustc_span::Span;
 
@@ -58,17 +58,10 @@ fn opaque_type_bounds<'tcx>(
     tcx: TyCtxt<'tcx>,
     opaque_def_id: DefId,
     ast_bounds: &'tcx [hir::GenericBound<'tcx>],
+    item_ty: Ty<'tcx>,
     span: Span,
-    in_trait: bool,
 ) -> &'tcx [(ty::Predicate<'tcx>, Span)] {
     ty::print::with_no_queries!({
-        let substs = InternalSubsts::identity_for_item(tcx, opaque_def_id);
-        let item_ty = if in_trait {
-            tcx.mk_projection(opaque_def_id, substs)
-        } else {
-            tcx.mk_opaque(opaque_def_id, substs)
-        };
-
         let icx = ItemCtxt::new(tcx, opaque_def_id);
         let mut bounds = icx.astconv().compute_bounds(item_ty, ast_bounds);
         // Opaque types are implicitly sized unless a `?Sized` bound is found
@@ -83,7 +76,16 @@ pub(super) fn explicit_item_bounds(
     tcx: TyCtxt<'_>,
     def_id: DefId,
 ) -> &'_ [(ty::Predicate<'_>, Span)] {
-    let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
+    let rpitit_info = if let Some(ImplTraitInTraitData::Trait { opaque_def_id, .. }) =
+        tcx.opt_rpitit_info(def_id)
+    {
+        Some(opaque_def_id)
+    } else {
+        None
+    };
+
+    let bounds_def_id = rpitit_info.unwrap_or(def_id);
+    let hir_id = tcx.hir().local_def_id_to_hir_id(bounds_def_id.expect_local());
     match tcx.hir().get(hir_id) {
         hir::Node::TraitItem(hir::TraitItem {
             kind: hir::TraitItemKind::Type(bounds, _),
@@ -94,7 +96,15 @@ pub(super) fn explicit_item_bounds(
             kind: hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds, in_trait, .. }),
             span,
             ..
-        }) => opaque_type_bounds(tcx, def_id, bounds, *span, *in_trait),
+        }) => {
+            let substs = InternalSubsts::identity_for_item(tcx, def_id);
+            let item_ty = if *in_trait && rpitit_info.is_none() {
+                tcx.mk_projection(def_id, substs)
+            } else {
+                tcx.mk_opaque(def_id, substs)
+            };
+            opaque_type_bounds(tcx, bounds_def_id, bounds, item_ty, *span)
+        }
         _ => bug!("item_bounds called on {:?}", def_id),
     }
 }

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -9,7 +9,8 @@ use rustc_middle::ty::print::with_forced_trimmed_paths;
 use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::util::IntTypeExt;
 use rustc_middle::ty::{
-    self, DefIdTree, IsSuggestable, Ty, TyCtxt, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
+    self, DefIdTree, ImplTraitInTraitData, IsSuggestable, Ty, TyCtxt, TypeFolder,
+    TypeSuperFoldable, TypeVisitableExt,
 };
 use rustc_span::symbol::Ident;
 use rustc_span::{Span, DUMMY_SP};
@@ -244,6 +245,21 @@ fn get_path_containing_arg_in_pat<'hir>(
 }
 
 pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::EarlyBinder<Ty<'_>> {
+    if let Some(ImplTraitInTraitData::Impl { fn_def_id, .. }) = tcx.opt_rpitit_info(def_id) {
+        match tcx.collect_return_position_impl_trait_in_trait_tys(fn_def_id) {
+            Ok(map) => {
+                let assoc_item = tcx.associated_item(def_id);
+                return ty::EarlyBinder(map[&assoc_item.trait_item_def_id.unwrap()]);
+            }
+            Err(_) => {
+                return ty::EarlyBinder(tcx.ty_error_with_message(
+                    DUMMY_SP,
+                    "Could not collect return position impl trait in trait tys",
+                ));
+            }
+        }
+    }
+
     let def_id = def_id.expect_local();
     use rustc_hir::*;
 

compiler/rustc_middle/src/query/mod.rs

@@ -1324,6 +1324,7 @@ rustc_queries! {
     /// might want to use `reveal_all()` method to change modes.
     query param_env(def_id: DefId) -> ty::ParamEnv<'tcx> {
         desc { |tcx| "computing normalized predicates of `{}`", tcx.def_path_str(def_id) }
+        feedable
     }
 
     /// Like `param_env`, but returns the `ParamEnv` in `Reveal::All` mode.

compiler/rustc_passes/src/dead.rs

@@ -243,6 +243,11 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
                 continue;
             }
 
+            if self.tcx.opt_rpitit_info(id).is_some() {
+                self.live_symbols.insert(id);
+                continue;
+            }
+
             // in the case of tuple struct constructors we want to check the item, not the generated
             // tuple struct constructor function
             let id = self.struct_constructors.get(&id).copied().unwrap_or(id);

compiler/rustc_ty_utils/src/assoc.rs

@@ -302,9 +302,6 @@ fn associated_item_for_impl_trait_in_trait(
     // There are no inferred outlives for the synthesized associated type.
     trait_assoc_ty.inferred_outlives_of(&[]);
 
-    // FIXME implement this.
-    trait_assoc_ty.explicit_item_bounds(&[]);
-
     local_def_id
 }
 
@@ -316,11 +313,12 @@ fn impl_associated_item_for_impl_trait_in_trait(
     trait_assoc_def_id: LocalDefId,
     impl_fn_def_id: LocalDefId,
 ) -> LocalDefId {
-    let impl_def_id = tcx.local_parent(impl_fn_def_id);
+    let impl_def_id = tcx.parent(impl_fn_def_id.to_def_id());
 
     // FIXME fix the span, we probably want the def_id of the return type of the function
     let span = tcx.def_span(impl_fn_def_id);
-    let impl_assoc_ty = tcx.at(span).create_def(impl_def_id, DefPathData::ImplTraitAssocTy);
+    let impl_assoc_ty =
+        tcx.at(span).create_def(impl_def_id.expect_local(), DefPathData::ImplTraitAssocTy);
 
     let local_def_id = impl_assoc_ty.def_id();
     let def_id = local_def_id.to_def_id();
@@ -345,13 +343,51 @@ fn impl_associated_item_for_impl_trait_in_trait(
         fn_has_self_parameter: false,
     });
 
+    impl_assoc_ty.param_env(tcx.param_env(impl_fn_def_id));
+
     // Copy impl_defaultness of the containing function.
     impl_assoc_ty.impl_defaultness(tcx.impl_defaultness(impl_fn_def_id));
 
-    // Copy generics_of the trait's associated item.
-    // FIXME: This is not correct, in particular the parent is going to be wrong. So we would need
-    // to copy from trait_assoc_def_id and adjust things.
-    impl_assoc_ty.generics_of(tcx.generics_of(trait_assoc_def_id).clone());
+    // Copy generics_of the trait's associated item but the impl as the parent.
+    impl_assoc_ty.generics_of({
+        let trait_assoc_generics = tcx.generics_of(trait_assoc_def_id);
+        let trait_assoc_parent_count = trait_assoc_generics.parent_count;
+        let mut params = trait_assoc_generics.params.clone();
+
+        let parent_generics = tcx.generics_of(impl_def_id);
+        let parent_count = parent_generics.parent_count + parent_generics.params.len();
+
+        let mut impl_fn_params = tcx.generics_of(impl_fn_def_id).params.clone();
+
+        for param in &mut params {
+            param.index = param.index + parent_count as u32 + impl_fn_params.len() as u32
+                - trait_assoc_parent_count as u32;
+        }
+
+        impl_fn_params.extend(params);
+        params = impl_fn_params;
+
+        let param_def_id_to_index =
+            params.iter().map(|param| (param.def_id, param.index)).collect();
+
+        ty::Generics {
+            parent: Some(impl_def_id),
+            parent_count,
+            params,
+            param_def_id_to_index,
+            has_self: false,
+            has_late_bound_regions: trait_assoc_generics.has_late_bound_regions,
+        }
+    });
+
+    // There are no predicates for the synthesized associated type.
+    impl_assoc_ty.explicit_predicates_of(ty::GenericPredicates {
+        parent: Some(impl_def_id),
+        predicates: &[],
+    });
+
+    // There are no inferred outlives for the synthesized associated type.
+    impl_assoc_ty.inferred_outlives_of(&[]);
 
     local_def_id
 }

compiler/rustc_ty_utils/src/ty.rs

@@ -3,8 +3,8 @@ use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_index::bit_set::BitSet;
 use rustc_middle::ty::{
-    self, Binder, EarlyBinder, Predicate, PredicateKind, ToPredicate, Ty, TyCtxt,
-    TypeSuperVisitable, TypeVisitable, TypeVisitor,
+    self, Binder, EarlyBinder, ImplTraitInTraitData, Predicate, PredicateKind, ToPredicate, Ty,
+    TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
 };
 use rustc_session::config::TraitSolver;
 use rustc_span::def_id::{DefId, CRATE_DEF_ID};
@@ -117,6 +117,13 @@ fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> &[Ty<'_>] {
 
 /// See `ParamEnv` struct definition for details.
 fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
+    let def_id =
+        if let Some(ImplTraitInTraitData::Trait { fn_def_id, .. }) = tcx.opt_rpitit_info(def_id) {
+            fn_def_id
+        } else {
+            def_id
+        };
+
     // Compute the bounds on Self and the type parameters.
     let ty::InstantiatedPredicates { mut predicates, .. } =
         tcx.predicates_of(def_id).instantiate_identity(tcx);

src/tools/compiletest/src/common.rs

@@ -123,6 +123,7 @@ pub enum FailMode {
 pub enum CompareMode {
     Polonius,
     Chalk,
+    LowerImplTraitInTraitToAssocTy,
     NextSolver,
     SplitDwarf,
     SplitDwarfSingle,
@@ -133,6 +134,7 @@ impl CompareMode {
         match *self {
             CompareMode::Polonius => "polonius",
             CompareMode::Chalk => "chalk",
+            CompareMode::LowerImplTraitInTraitToAssocTy => "lower-impl-trait-in-trait-to-assoc-ty",
             CompareMode::NextSolver => "next-solver",
             CompareMode::SplitDwarf => "split-dwarf",
             CompareMode::SplitDwarfSingle => "split-dwarf-single",
@@ -143,6 +145,7 @@ impl CompareMode {
         match s.as_str() {
             "polonius" => CompareMode::Polonius,
             "chalk" => CompareMode::Chalk,
+            "lower-impl-trait-in-trait-to-assoc-ty" => CompareMode::LowerImplTraitInTraitToAssocTy,
             "next-solver" => CompareMode::NextSolver,
             "split-dwarf" => CompareMode::SplitDwarf,
             "split-dwarf-single" => CompareMode::SplitDwarfSingle,

src/tools/compiletest/src/header.rs

@@ -710,6 +710,7 @@ impl Config {
             match self.compare_mode {
                 Some(CompareMode::Polonius) => name == "compare-mode-polonius",
                 Some(CompareMode::Chalk) => name == "compare-mode-chalk",
+                Some(CompareMode::LowerImplTraitInTraitToAssocTy) => name == "compare-mode-lower-impl-trait-in-trait-to-assoc-ty",
                 Some(CompareMode::NextSolver) => name == "compare-mode-next-solver",
                 Some(CompareMode::SplitDwarf) => name == "compare-mode-split-dwarf",
                 Some(CompareMode::SplitDwarfSingle) => name == "compare-mode-split-dwarf-single",

src/tools/compiletest/src/runtest.rs

@@ -2030,6 +2030,9 @@ impl<'test> TestCx<'test> {
             Some(CompareMode::Chalk) => {
                 rustc.args(&["-Ztrait-solver=chalk"]);
             }
+            Some(CompareMode::LowerImplTraitInTraitToAssocTy) => {
+                rustc.args(&["-Zlower-impl-trait-in-trait-to-assoc-ty"]);
+            }
             Some(CompareMode::NextSolver) => {
                 rustc.args(&["-Ztrait-solver=next"]);
             }

tests/ui/async-await/async-trait-fn.rs

@@ -1,3 +1,4 @@
+// ignore-compare-mode-lower-impl-trait-in-trait-to-assoc-ty
 // edition:2018
 trait T {
     async fn foo() {} //~ ERROR functions in traits cannot be declared `async`

tests/ui/async-await/async-trait-fn.stderr

@@ -1,5 +1,5 @@
 error[E0706]: functions in traits cannot be declared `async`
-  --> $DIR/async-trait-fn.rs:3:5
+  --> $DIR/async-trait-fn.rs:4:5
    |
 LL |     async fn foo() {}
    |     -----^^^^^^^^^
@@ -12,7 +12,7 @@ LL |     async fn foo() {}
    = help: add `#![feature(async_fn_in_trait)]` to the crate attributes to enable
 
 error[E0706]: functions in traits cannot be declared `async`
-  --> $DIR/async-trait-fn.rs:4:5
+  --> $DIR/async-trait-fn.rs:5:5
    |
 LL |     async fn bar(&self) {}
    |     -----^^^^^^^^^^^^^^
@@ -25,7 +25,7 @@ LL |     async fn bar(&self) {}
    = help: add `#![feature(async_fn_in_trait)]` to the crate attributes to enable
 
 error[E0706]: functions in traits cannot be declared `async`
-  --> $DIR/async-trait-fn.rs:5:5
+  --> $DIR/async-trait-fn.rs:6:5
    |
 LL |     async fn baz() {
    |     -----^^^^^^^^^

tests/ui/async-await/edition-deny-async-fns-2015.rs

@@ -1,4 +1,5 @@
 // edition:2015
+// ignore-compare-mode-lower-impl-trait-in-trait-to-assoc-ty
 
 async fn foo() {} //~ ERROR `async fn` is not permitted in Rust 2015