Remove existing AFIDT implementation

compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs

@@ -176,7 +176,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                                 .in_definition_order()
                                 // We only care about associated types.
                                 .filter(|item| item.kind == ty::AssocKind::Type)
-                                // No RPITITs -- even with `async_fn_in_dyn_trait`, they are implicit.
+                                // No RPITITs -- they're not dyn-compatible for now.
                                 .filter(|item| !item.is_impl_trait_in_trait())
                                 // If the associated type has a `where Self: Sized` bound,
                                 // we do not need to constrain the associated type.

compiler/rustc_middle/src/ty/instance.rs

@@ -712,10 +712,7 @@ impl<'tcx> Instance<'tcx> {
                             ..
                         })
                     );
-                // We also need to generate a shim if this is an AFIT.
-                let needs_rpitit_shim =
-                    tcx.return_position_impl_trait_in_trait_shim_data(def).is_some();
-                if needs_track_caller_shim || needs_rpitit_shim {
+                if needs_track_caller_shim {
                     if tcx.is_closure_like(def) {
                         debug!(
                             " => vtable fn pointer created for closure with #[track_caller]: {:?} for method {:?} {:?}",

compiler/rustc_middle/src/ty/mod.rs

@@ -149,7 +149,6 @@ mod opaque_types;
 mod parameterized;
 mod predicate;
 mod region;
-mod return_position_impl_trait_in_trait;
 mod rvalue_scopes;
 mod structural_impls;
 #[allow(hidden_glob_reexports)]

compiler/rustc_mir_transform/src/shim.rs

@@ -8,7 +8,6 @@ use rustc_hir::lang_items::LangItem;
 use rustc_index::{Idx, IndexVec};
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::{
     self, CoroutineArgs, CoroutineArgsExt, EarlyBinder, GenericArgs, Ty, TyCtxt,
 };
@@ -718,12 +717,6 @@ fn build_call_shim<'tcx>(
 
     let def_id = instance.def_id();
 
-    let rpitit_shim = if let ty::InstanceKind::ReifyShim(..) = instance {
-        tcx.return_position_impl_trait_in_trait_shim_data(def_id)
-    } else {
-        None
-    };
-
     let sig = tcx.fn_sig(def_id);
     let sig = sig.map_bound(|sig| tcx.instantiate_bound_regions_with_erased(sig));
 
@@ -779,30 +772,7 @@ fn build_call_shim<'tcx>(
     let mut local_decls = local_decls_for_sig(&sig, span);
     let source_info = SourceInfo::outermost(span);
 
-    let mut destination = Place::return_place();
-    if let Some((rpitit_def_id, fn_args)) = rpitit_shim {
-        let rpitit_args =
-            fn_args.instantiate_identity().extend_to(tcx, rpitit_def_id, |param, _| {
-                match param.kind {
-                    ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
-                    ty::GenericParamDefKind::Type { .. }
-                    | ty::GenericParamDefKind::Const { .. } => {
-                        unreachable!("rpitit should have no addition ty/ct")
-                    }
-                }
-            });
-        let dyn_star_ty = Ty::new_dynamic(
-            tcx,
-            tcx.item_bounds_to_existential_predicates(rpitit_def_id, rpitit_args),
-            tcx.lifetimes.re_erased,
-            ty::DynStar,
-        );
-        destination = local_decls.push(local_decls[RETURN_PLACE].clone()).into();
-        local_decls[RETURN_PLACE].ty = dyn_star_ty;
-        let mut inputs_and_output = sig.inputs_and_output.to_vec();
-        *inputs_and_output.last_mut().unwrap() = dyn_star_ty;
-        sig.inputs_and_output = tcx.mk_type_list(&inputs_and_output);
-    }
+    let destination = Place::return_place();
 
     let rcvr_place = || {
         assert!(rcvr_adjustment.is_some());
@@ -921,23 +891,7 @@ fn build_call_shim<'tcx>(
         );
     }
     // BB #1/#2 - return
-    // NOTE: If this is an RPITIT in dyn, we also want to coerce
-    // the return type of the function into a `dyn*`.
-    let stmts = if rpitit_shim.is_some() {
-        vec![Statement {
-            source_info,
-            kind: StatementKind::Assign(Box::new((
-                Place::return_place(),
-                Rvalue::Cast(
-                    CastKind::PointerCoercion(PointerCoercion::DynStar, CoercionSource::Implicit),
-                    Operand::Move(destination),
-                    sig.output(),
-                ),
-            ))),
-        }]
-    } else {
-        vec![]
-    };
+    let stmts = vec![];
     block(&mut blocks, stmts, TerminatorKind::Return, false);
     if let Some(Adjustment::RefMut) = rcvr_adjustment {
         // BB #3 - drop if closure panics

compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs

@@ -9,7 +9,6 @@ use std::ops::ControlFlow;
 use rustc_errors::FatalError;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{
     self, EarlyBinder, GenericArgs, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
@@ -807,31 +806,8 @@ fn contains_illegal_impl_trait_in_trait<'tcx>(
     let ty = tcx.liberate_late_bound_regions(fn_def_id, ty);
 
     if tcx.asyncness(fn_def_id).is_async() {
-        // FIXME(async_fn_in_dyn_trait): Think of a better way to unify these code paths
-        // to issue an appropriate feature suggestion when users try to use AFIDT.
-        // Obviously we must only do this once AFIDT is finished enough to actually be usable.
-        if tcx.features().async_fn_in_dyn_trait() {
-            let ty::Alias(ty::Projection, proj) = *ty.kind() else {
-                bug!("expected async fn in trait to return an RPITIT");
-            };
-            assert!(tcx.is_impl_trait_in_trait(proj.def_id));
-
-            // FIXME(async_fn_in_dyn_trait): We should check that this bound is legal too,
-            // and stop relying on `async fn` in the definition.
-            for bound in tcx.item_bounds(proj.def_id).instantiate(tcx, proj.args) {
-                if let Some(violation) = bound
-                    .visit_with(&mut IllegalRpititVisitor { tcx, allowed: Some(proj) })
-                    .break_value()
-                {
-                    return Some(violation);
-                }
-            }
-
-            None
-        } else {
-            // Rendering the error as a separate `async-specific` message is better.
-            Some(MethodViolationCode::AsyncFn)
-        }
+        // Rendering the error as a separate `async-specific` message is better.
+        Some(MethodViolationCode::AsyncFn)
     } else {
         ty.visit_with(&mut IllegalRpititVisitor { tcx, allowed: None }).break_value()
     }

compiler/rustc_trait_selection/src/traits/project.rs

@@ -7,8 +7,8 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def::DefKind;
 use rustc_hir::lang_items::LangItem;
+use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_infer::infer::resolve::OpportunisticRegionResolver;
-use rustc_infer::infer::{DefineOpaqueTypes, RegionVariableOrigin};
 use rustc_infer::traits::{ObligationCauseCode, PredicateObligations};
 use rustc_middle::traits::select::OverflowError;
 use rustc_middle::traits::{BuiltinImplSource, ImplSource, ImplSourceUserDefinedData};
@@ -18,8 +18,6 @@ use rustc_middle::ty::{
 };
 use rustc_middle::{bug, span_bug};
 use rustc_span::sym;
-use rustc_type_ir::elaborate;
-use thin_vec::thin_vec;
 use tracing::{debug, instrument};
 
 use super::{
@@ -63,9 +61,6 @@ enum ProjectionCandidate<'tcx> {
     /// Bounds specified on an object type
     Object(ty::PolyProjectionPredicate<'tcx>),
 
-    /// Built-in bound for a dyn async fn in trait
-    ObjectRpitit,
-
     /// From an "impl" (or a "pseudo-impl" returned by select)
     Select(Selection<'tcx>),
 }
@@ -832,16 +827,6 @@ fn assemble_candidates_from_object_ty<'cx, 'tcx>(
         env_predicates,
         false,
     );
-
-    // `dyn Trait` automagically project their AFITs to `dyn* Future`.
-    if tcx.is_impl_trait_in_trait(obligation.predicate.def_id)
-        && let Some(out_trait_def_id) = data.principal_def_id()
-        && let rpitit_trait_def_id = tcx.parent(obligation.predicate.def_id)
-        && elaborate::supertrait_def_ids(tcx, out_trait_def_id)
-            .any(|trait_def_id| trait_def_id == rpitit_trait_def_id)
-    {
-        candidate_set.push_candidate(ProjectionCandidate::ObjectRpitit);
-    }
 }
 
 #[instrument(
@@ -1273,8 +1258,6 @@ fn confirm_candidate<'cx, 'tcx>(
         ProjectionCandidate::Select(impl_source) => {
             confirm_select_candidate(selcx, obligation, impl_source)
         }
-
-        ProjectionCandidate::ObjectRpitit => confirm_object_rpitit_candidate(selcx, obligation),
     };
 
     // When checking for cycle during evaluation, we compare predicates with
@@ -2070,45 +2053,6 @@ fn confirm_impl_candidate<'cx, 'tcx>(
     }
 }
 
-fn confirm_object_rpitit_candidate<'cx, 'tcx>(
-    selcx: &mut SelectionContext<'cx, 'tcx>,
-    obligation: &ProjectionTermObligation<'tcx>,
-) -> Progress<'tcx> {
-    let tcx = selcx.tcx();
-    let mut obligations = thin_vec![];
-
-    // Compute an intersection lifetime for all the input components of this GAT.
-    let intersection =
-        selcx.infcx.next_region_var(RegionVariableOrigin::MiscVariable(obligation.cause.span));
-    for component in obligation.predicate.args {
-        match component.unpack() {
-            ty::GenericArgKind::Lifetime(lt) => {
-                obligations.push(obligation.with(tcx, ty::OutlivesPredicate(lt, intersection)));
-            }
-            ty::GenericArgKind::Type(ty) => {
-                obligations.push(obligation.with(tcx, ty::OutlivesPredicate(ty, intersection)));
-            }
-            ty::GenericArgKind::Const(_ct) => {
-                // Consts have no outlives...
-            }
-        }
-    }
-
-    Progress {
-        term: Ty::new_dynamic(
-            tcx,
-            tcx.item_bounds_to_existential_predicates(
-                obligation.predicate.def_id,
-                obligation.predicate.args,
-            ),
-            intersection,
-            ty::DynStar,
-        )
-        .into(),
-        obligations,
-    }
-}
-
 // Get obligations corresponding to the predicates from the where-clause of the
 // associated type itself.
 fn assoc_ty_own_obligations<'cx, 'tcx>(

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -616,12 +616,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         for assoc_type in assoc_types {
             let defs: &ty::Generics = tcx.generics_of(assoc_type);
 
-            // When `async_fn_in_dyn_trait` is enabled, we don't need to check the
-            // RPITIT for compatibility, since it's not provided by the user.
-            if tcx.features().async_fn_in_dyn_trait() && tcx.is_impl_trait_in_trait(assoc_type) {
-                continue;
-            }
-
             if !defs.own_params.is_empty() {
                 tcx.dcx().span_delayed_bug(
                     obligation.cause.span,

compiler/rustc_ty_utils/src/abi.rs

@@ -55,31 +55,6 @@ fn fn_sig_for_fn_abi<'tcx>(
                 sig.inputs_and_output = tcx.mk_type_list(&inputs_and_output);
             }
 
-            // Modify `fn() -> impl Future` to `fn() -> dyn* Future`.
-            if let ty::InstanceKind::ReifyShim(def_id, _) = instance.def
-                && let Some((rpitit_def_id, fn_args)) =
-                    tcx.return_position_impl_trait_in_trait_shim_data(def_id)
-            {
-                let fn_args = fn_args.instantiate(tcx, args);
-                let rpitit_args =
-                    fn_args.extend_to(tcx, rpitit_def_id, |param, _| match param.kind {
-                        ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
-                        ty::GenericParamDefKind::Type { .. }
-                        | ty::GenericParamDefKind::Const { .. } => {
-                            unreachable!("rpitit should have no addition ty/ct")
-                        }
-                    });
-                let dyn_star_ty = Ty::new_dynamic(
-                    tcx,
-                    tcx.item_bounds_to_existential_predicates(rpitit_def_id, rpitit_args),
-                    tcx.lifetimes.re_erased,
-                    ty::DynStar,
-                );
-                let mut inputs_and_output = sig.inputs_and_output.to_vec();
-                *inputs_and_output.last_mut().unwrap() = dyn_star_ty;
-                sig.inputs_and_output = tcx.mk_type_list(&inputs_and_output);
-            }
-
             sig
         }
         ty::Closure(def_id, args) => {