Rollup of 7 pull requests

.gitignore

@@ -86,4 +86,13 @@ package.json
 ## Rustdoc GUI tests
 tests/rustdoc-gui/src/**.lock
 
+## direnv
+.envrc
+.direnv/
+
+## nix
+flake.nix
+flake.lock
+default.nix
+
 # Before adding new lines, see the comment at the top.

compiler/rustc_ast_lowering/src/item.rs

@@ -286,7 +286,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                                 parent: this.local_def_id(id),
                                 in_assoc_ty: false,
                             },
-                            fn_kind: None,
                         }),
                     },
                 );
@@ -983,7 +982,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                                     parent: this.local_def_id(i.id),
                                     in_assoc_ty: true,
                                 },
-                                fn_kind: None,
                             });
                             hir::ImplItemKind::Type(ty)
                         }

compiler/rustc_ast_lowering/src/lib.rs

@@ -288,12 +288,7 @@ enum ImplTraitContext {
     /// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
     /// equivalent to a new opaque type like `type T = impl Debug; fn foo() -> T`.
     ///
-    OpaqueTy {
-        origin: hir::OpaqueTyOrigin,
-        /// Only used to change the lifetime capture rules, since
-        /// RPITIT captures all in scope, RPIT does not.
-        fn_kind: Option<FnDeclKind>,
-    },
+    OpaqueTy { origin: hir::OpaqueTyOrigin },
     /// `impl Trait` is unstably accepted in this position.
     FeatureGated(ImplTraitPosition, Symbol),
     /// `impl Trait` is not accepted in this position.
@@ -1404,14 +1399,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             TyKind::ImplTrait(def_node_id, bounds) => {
                 let span = t.span;
                 match itctx {
-                    ImplTraitContext::OpaqueTy { origin, fn_kind } => self.lower_opaque_impl_trait(
-                        span,
-                        origin,
-                        *def_node_id,
-                        bounds,
-                        fn_kind,
-                        itctx,
-                    ),
+                    ImplTraitContext::OpaqueTy { origin } => {
+                        self.lower_opaque_impl_trait(span, origin, *def_node_id, bounds, itctx)
+                    }
                     ImplTraitContext::Universal => {
                         if let Some(span) = bounds.iter().find_map(|bound| match *bound {
                             ast::GenericBound::Use(_, span) => Some(span),
@@ -1513,7 +1503,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         origin: hir::OpaqueTyOrigin,
         opaque_ty_node_id: NodeId,
         bounds: &GenericBounds,
-        fn_kind: Option<FnDeclKind>,
         itctx: ImplTraitContext,
     ) -> hir::TyKind<'hir> {
         // Make sure we know that some funky desugaring has been going on here.
@@ -1555,11 +1544,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         .map(|(ident, id, _)| Lifetime { id, ident })
                         .collect()
                 }
-                hir::OpaqueTyOrigin::FnReturn(..) => {
-                    if matches!(
-                        fn_kind.expect("expected RPITs to be lowered with a FnKind"),
-                        FnDeclKind::Impl | FnDeclKind::Trait
-                    ) || self.tcx.features().lifetime_capture_rules_2024
+                hir::OpaqueTyOrigin::FnReturn { in_trait_or_impl, .. } => {
+                    if in_trait_or_impl.is_some()
+                        || self.tcx.features().lifetime_capture_rules_2024
                         || span.at_least_rust_2024()
                     {
                         // return-position impl trait in trait was decided to capture all
@@ -1576,37 +1563,29 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         lifetime_collector::lifetimes_in_bounds(self.resolver, bounds)
                     }
                 }
-                hir::OpaqueTyOrigin::AsyncFn(..) => {
+                hir::OpaqueTyOrigin::AsyncFn { .. } => {
                     unreachable!("should be using `lower_async_fn_ret_ty`")
                 }
             }
         };
         debug!(?captured_lifetimes_to_duplicate);
 
-        match fn_kind {
-            // Deny `use<>` on RPITIT in trait/trait-impl for now.
-            Some(FnDeclKind::Trait | FnDeclKind::Impl) => {
+        // Feature gate for RPITIT + use<..>
+        match origin {
+            rustc_hir::OpaqueTyOrigin::FnReturn { in_trait_or_impl: Some(_), .. } => {
                 if let Some(span) = bounds.iter().find_map(|bound| match *bound {
                     ast::GenericBound::Use(_, span) => Some(span),
                     _ => None,
                 }) {
                     self.tcx.dcx().emit_err(errors::NoPreciseCapturesOnRpitit { span });
                 }
             }
-            None
-            | Some(
-                FnDeclKind::Fn
-                | FnDeclKind::Inherent
-                | FnDeclKind::ExternFn
-                | FnDeclKind::Closure
-                | FnDeclKind::Pointer,
-            ) => {}
+            _ => {}
         }
 
         self.lower_opaque_inner(
             opaque_ty_node_id,
             origin,
-            matches!(fn_kind, Some(FnDeclKind::Trait)),
             captured_lifetimes_to_duplicate,
             span,
             opaque_ty_span,
@@ -1618,7 +1597,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         &mut self,
         opaque_ty_node_id: NodeId,
         origin: hir::OpaqueTyOrigin,
-        in_trait: bool,
         captured_lifetimes_to_duplicate: FxIndexSet<Lifetime>,
         span: Span,
         opaque_ty_span: Span,
@@ -1747,7 +1725,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 bounds,
                 origin,
                 lifetime_mapping,
-                in_trait,
             };
 
             // Generate an `type Foo = impl Trait;` declaration.
@@ -1776,7 +1753,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         hir::TyKind::OpaqueDef(
             hir::ItemId { owner_id: hir::OwnerId { def_id: opaque_ty_def_id } },
             generic_args,
-            in_trait,
         )
     }
 
@@ -1864,12 +1840,23 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             None => match &decl.output {
                 FnRetTy::Ty(ty) => {
                     let itctx = match kind {
-                        FnDeclKind::Fn
-                        | FnDeclKind::Inherent
-                        | FnDeclKind::Trait
-                        | FnDeclKind::Impl => ImplTraitContext::OpaqueTy {
-                            origin: hir::OpaqueTyOrigin::FnReturn(self.local_def_id(fn_node_id)),
-                            fn_kind: Some(kind),
+                        FnDeclKind::Fn | FnDeclKind::Inherent => ImplTraitContext::OpaqueTy {
+                            origin: hir::OpaqueTyOrigin::FnReturn {
+                                parent: self.local_def_id(fn_node_id),
+                                in_trait_or_impl: None,
+                            },
+                        },
+                        FnDeclKind::Trait => ImplTraitContext::OpaqueTy {
+                            origin: hir::OpaqueTyOrigin::FnReturn {
+                                parent: self.local_def_id(fn_node_id),
+                                in_trait_or_impl: Some(hir::RpitContext::Trait),
+                            },
+                        },
+                        FnDeclKind::Impl => ImplTraitContext::OpaqueTy {
+                            origin: hir::OpaqueTyOrigin::FnReturn {
+                                parent: self.local_def_id(fn_node_id),
+                                in_trait_or_impl: Some(hir::RpitContext::TraitImpl),
+                            },
                         },
                         FnDeclKind::ExternFn => {
                             ImplTraitContext::Disallowed(ImplTraitPosition::ExternFnReturn)
@@ -1951,10 +1938,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             .map(|(ident, id, _)| Lifetime { id, ident })
             .collect();
 
+        let in_trait_or_impl = match fn_kind {
+            FnDeclKind::Trait => Some(hir::RpitContext::Trait),
+            FnDeclKind::Impl => Some(hir::RpitContext::TraitImpl),
+            FnDeclKind::Fn | FnDeclKind::Inherent => None,
+            FnDeclKind::ExternFn | FnDeclKind::Closure | FnDeclKind::Pointer => unreachable!(),
+        };
+
         let opaque_ty_ref = self.lower_opaque_inner(
             opaque_ty_node_id,
-            hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
-            matches!(fn_kind, FnDeclKind::Trait),
+            hir::OpaqueTyOrigin::AsyncFn { parent: fn_def_id, in_trait_or_impl },
             captured_lifetimes,
             span,
             opaque_ty_span,
@@ -1964,8 +1957,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     coro,
                     opaque_ty_span,
                     ImplTraitContext::OpaqueTy {
-                        origin: hir::OpaqueTyOrigin::FnReturn(fn_def_id),
-                        fn_kind: Some(fn_kind),
+                        origin: hir::OpaqueTyOrigin::FnReturn {
+                            parent: fn_def_id,
+                            in_trait_or_impl,
+                        },
                     },
                 );
                 arena_vec![this; bound]

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -832,7 +832,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
     fn get_future_inner_return_ty(&self, hir_ty: &'tcx hir::Ty<'tcx>) -> &'tcx hir::Ty<'tcx> {
         let hir = self.infcx.tcx.hir();
 
-        let hir::TyKind::OpaqueDef(id, _, _) = hir_ty.kind else {
+        let hir::TyKind::OpaqueDef(id, _) = hir_ty.kind else {
             span_bug!(
                 hir_ty.span,
                 "lowered return type of async fn is not OpaqueDef: {:?}",

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -503,8 +503,8 @@ impl<'tcx> LazyOpaqueTyEnv<'tcx> {
         let &Self { tcx, def_id, .. } = self;
         let origin = tcx.opaque_type_origin(def_id);
         let parent = match origin {
-            hir::OpaqueTyOrigin::FnReturn(parent)
-            | hir::OpaqueTyOrigin::AsyncFn(parent)
+            hir::OpaqueTyOrigin::FnReturn { parent, .. }
+            | hir::OpaqueTyOrigin::AsyncFn { parent, .. }
             | hir::OpaqueTyOrigin::TyAlias { parent, .. } => parent,
         };
         let param_env = tcx.param_env(parent);

compiler/rustc_hir/src/hir.rs

@@ -2632,7 +2632,7 @@ impl<'hir> Ty<'hir> {
             }
             TyKind::Tup(tys) => tys.iter().any(Self::is_suggestable_infer_ty),
             TyKind::Ptr(mut_ty) | TyKind::Ref(_, mut_ty) => mut_ty.ty.is_suggestable_infer_ty(),
-            TyKind::OpaqueDef(_, generic_args, _) => are_suggestable_generic_args(generic_args),
+            TyKind::OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
             TyKind::Path(QPath::TypeRelative(ty, segment)) => {
                 ty.is_suggestable_infer_ty() || are_suggestable_generic_args(segment.args().args)
             }
@@ -2762,10 +2762,6 @@ pub struct OpaqueTy<'hir> {
     /// This mapping associated a captured lifetime (first parameter) with the new
     /// early-bound lifetime that was generated for the opaque.
     pub lifetime_mapping: &'hir [(&'hir Lifetime, LocalDefId)],
-    /// Whether the opaque is a return-position impl trait (or async future)
-    /// originating from a trait method. This makes it so that the opaque is
-    /// lowered as an associated type.
-    pub in_trait: bool,
 }
 
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
@@ -2802,13 +2798,29 @@ pub struct PreciseCapturingNonLifetimeArg {
     pub res: Res,
 }
 
+#[derive(Copy, Clone, PartialEq, Eq, Debug, HashStable_Generic)]
+pub enum RpitContext {
+    Trait,
+    TraitImpl,
+}
+
 /// From whence the opaque type came.
 #[derive(Copy, Clone, PartialEq, Eq, Debug, HashStable_Generic)]
 pub enum OpaqueTyOrigin {
     /// `-> impl Trait`
-    FnReturn(LocalDefId),
+    FnReturn {
+        /// The defining function.
+        parent: LocalDefId,
+        // Whether this is an RPITIT (return position impl trait in trait)
+        in_trait_or_impl: Option<RpitContext>,
+    },
     /// `async fn`
-    AsyncFn(LocalDefId),
+    AsyncFn {
+        /// The defining function.
+        parent: LocalDefId,
+        // Whether this is an AFIT (async fn in trait)
+        in_trait_or_impl: Option<RpitContext>,
+    },
     /// type aliases: `type Foo = impl Trait;`
     TyAlias {
         /// The type alias or associated type parent of the TAIT/ATPIT
@@ -2856,7 +2868,7 @@ pub enum TyKind<'hir> {
     /// possibly parameters) that are actually bound on the `impl Trait`.
     ///
     /// The last parameter specifies whether this opaque appears in a trait definition.
-    OpaqueDef(ItemId, &'hir [GenericArg<'hir>], bool),
+    OpaqueDef(ItemId, &'hir [GenericArg<'hir>]),
     /// A trait object type `Bound1 + Bound2 + Bound3`
     /// where `Bound` is a trait or a lifetime.
     TraitObject(

compiler/rustc_hir/src/intravisit.rs

@@ -894,7 +894,7 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty<'v>) -> V::Resul
         TyKind::Path(ref qpath) => {
             try_visit!(visitor.visit_qpath(qpath, typ.hir_id, typ.span));
         }
-        TyKind::OpaqueDef(item_id, lifetimes, _in_trait) => {
+        TyKind::OpaqueDef(item_id, lifetimes) => {
             try_visit!(visitor.visit_nested_item(item_id));
             walk_list!(visitor, visit_generic_arg, lifetimes);
         }

compiler/rustc_hir_analysis/src/check/check.rs

@@ -336,18 +336,18 @@ fn check_opaque_meets_bounds<'tcx>(
     origin: &hir::OpaqueTyOrigin,
 ) -> Result<(), ErrorGuaranteed> {
     let defining_use_anchor = match *origin {
-        hir::OpaqueTyOrigin::FnReturn(did)
-        | hir::OpaqueTyOrigin::AsyncFn(did)
-        | hir::OpaqueTyOrigin::TyAlias { parent: did, .. } => did,
+        hir::OpaqueTyOrigin::FnReturn { parent, .. }
+        | hir::OpaqueTyOrigin::AsyncFn { parent, .. }
+        | hir::OpaqueTyOrigin::TyAlias { parent, .. } => parent,
     };
     let param_env = tcx.param_env(defining_use_anchor);
 
     let infcx = tcx.infer_ctxt().with_opaque_type_inference(defining_use_anchor).build();
     let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
 
     let args = match *origin {
-        hir::OpaqueTyOrigin::FnReturn(parent)
-        | hir::OpaqueTyOrigin::AsyncFn(parent)
+        hir::OpaqueTyOrigin::FnReturn { parent, .. }
+        | hir::OpaqueTyOrigin::AsyncFn { parent, .. }
         | hir::OpaqueTyOrigin::TyAlias { parent, .. } => GenericArgs::identity_for_item(
             tcx, parent,
         )
@@ -409,7 +409,7 @@ fn check_opaque_meets_bounds<'tcx>(
     let outlives_env = OutlivesEnvironment::with_bounds(param_env, implied_bounds);
     ocx.resolve_regions_and_report_errors(defining_use_anchor, &outlives_env)?;
 
-    if let hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..) = origin {
+    if let hir::OpaqueTyOrigin::FnReturn { .. } | hir::OpaqueTyOrigin::AsyncFn { .. } = origin {
         // HACK: this should also fall through to the hidden type check below, but the original
         // implementation had a bug where equivalent lifetimes are not identical. This caused us
         // to reject existing stable code that is otherwise completely fine. The real fix is to
@@ -736,8 +736,8 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
             check_opaque_precise_captures(tcx, def_id);
 
             let origin = tcx.opaque_type_origin(def_id);
-            if let hir::OpaqueTyOrigin::FnReturn(fn_def_id)
-            | hir::OpaqueTyOrigin::AsyncFn(fn_def_id) = origin
+            if let hir::OpaqueTyOrigin::FnReturn { parent: fn_def_id, .. }
+            | hir::OpaqueTyOrigin::AsyncFn { parent: fn_def_id, .. } = origin
                 && let hir::Node::TraitItem(trait_item) = tcx.hir_node_by_def_id(fn_def_id)
                 && let (_, hir::TraitFn::Required(..)) = trait_item.expect_fn()
             {

compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs

@@ -94,8 +94,8 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
         if !tcx.hir().get_if_local(impl_opaque.def_id).is_some_and(|node| {
             matches!(
                 node.expect_item().expect_opaque_ty().origin,
-                hir::OpaqueTyOrigin::AsyncFn(def_id)  | hir::OpaqueTyOrigin::FnReturn(def_id)
-                    if def_id == impl_m.def_id.expect_local()
+                hir::OpaqueTyOrigin::AsyncFn { parent, .. }  | hir::OpaqueTyOrigin::FnReturn { parent, .. }
+                    if parent == impl_m.def_id.expect_local()
             )
         }) {
             report_mismatched_rpitit_signature(

compiler/rustc_hir_analysis/src/collect/generics_of.rs

@@ -210,11 +210,11 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
         Node::Item(item) => match item.kind {
             ItemKind::OpaqueTy(&hir::OpaqueTy {
                 origin:
-                    hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
-                in_trait,
+                    hir::OpaqueTyOrigin::FnReturn { parent: fn_def_id, in_trait_or_impl }
+                    | hir::OpaqueTyOrigin::AsyncFn { parent: fn_def_id, in_trait_or_impl },
                 ..
             }) => {
-                if in_trait {
+                if in_trait_or_impl.is_some() {
                     assert_matches!(tcx.def_kind(fn_def_id), DefKind::AssocFn);
                 } else {
                     assert_matches!(tcx.def_kind(fn_def_id), DefKind::AssocFn | DefKind::Fn);