Simplify even more candidates

6 files changed, 88 insertions, 161 deletions

diff --git a/compiler/rustc_const_eval/src/transform/check_consts/check.rs b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
index 57d939747aa..d4cde7e2c65 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
@@ -781,8 +781,13 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                             );
                             return;
                         }
-                        Ok(Some(ImplSource::Closure(data))) => {
-                            if !tcx.is_const_fn_raw(data.closure_def_id) {
+                        Ok(Some(ImplSource::Closure(_))) => {
+                            let ty::Closure(closure_def_id, substs) =
+                                *poly_trait_pred.self_ty().no_bound_vars().unwrap().kind()
+                            else {
+                                unreachable!()
+                            };
+                            if !tcx.is_const_fn_raw(closure_def_id) {
                                 self.check_op(ops::FnCallNonConst {
                                     caller,
                                     callee,
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index a39f3ae7b4d..98179c0f933 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -664,16 +664,16 @@ pub enum ImplSource<'tcx, N> {
     /// ImplSource automatically generated for a closure. The `DefId` is the ID
     /// of the closure expression. This is an `ImplSource::UserDefined` in spirit, but the
     /// impl is generated by the compiler and does not appear in the source.
-    Closure(ImplSourceClosureData<'tcx, N>),
+    Closure(Vec<N>),
 
     /// Same as above, but for a function pointer type with the given signature.
-    FnPointer(ImplSourceFnPointerData<'tcx, N>),
+    FnPointer(Vec<N>),
 
     /// ImplSource automatically generated for a generator.
-    Generator(ImplSourceGeneratorData<'tcx, N>),
+    Generator(Vec<N>),
 
     /// ImplSource automatically generated for a generator backing an async future.
-    Future(ImplSourceFutureData<'tcx, N>),
+    Future(Vec<N>),
 
     /// ImplSource for a trait alias.
     TraitAlias(ImplSourceTraitAliasData<'tcx, N>),
@@ -683,12 +683,13 @@ impl<'tcx, N> ImplSource<'tcx, N> {
     pub fn nested_obligations(self) -> Vec<N> {
         match self {
             ImplSource::UserDefined(i) => i.nested,
-            ImplSource::Param(n, _) | ImplSource::Builtin(n) => n,
-            ImplSource::Closure(c) => c.nested,
-            ImplSource::Generator(c) => c.nested,
-            ImplSource::Future(c) => c.nested,
+            ImplSource::Param(n, _)
+            | ImplSource::Builtin(n)
+            | ImplSource::FnPointer(n)
+            | ImplSource::Closure(n)
+            | ImplSource::Generator(n)
+            | ImplSource::Future(n) => n,
             ImplSource::Object(d) => d.nested,
-            ImplSource::FnPointer(d) => d.nested,
             ImplSource::TraitAlias(d) => d.nested,
             ImplSource::TraitUpcasting(d) => d.nested,
         }
@@ -697,12 +698,13 @@ impl<'tcx, N> ImplSource<'tcx, N> {
     pub fn borrow_nested_obligations(&self) -> &[N] {
         match self {
             ImplSource::UserDefined(i) => &i.nested,
-            ImplSource::Param(n, _) | ImplSource::Builtin(n) => n,
-            ImplSource::Closure(c) => &c.nested,
-            ImplSource::Generator(c) => &c.nested,
-            ImplSource::Future(c) => &c.nested,
+            ImplSource::Param(n, _)
+            | ImplSource::Builtin(n)
+            | ImplSource::FnPointer(n)
+            | ImplSource::Closure(n)
+            | ImplSource::Generator(n)
+            | ImplSource::Future(n) => &n,
             ImplSource::Object(d) => &d.nested,
-            ImplSource::FnPointer(d) => &d.nested,
             ImplSource::TraitAlias(d) => &d.nested,
             ImplSource::TraitUpcasting(d) => &d.nested,
         }
@@ -711,12 +713,13 @@ impl<'tcx, N> ImplSource<'tcx, N> {
     pub fn borrow_nested_obligations_mut(&mut self) -> &mut [N] {
         match self {
             ImplSource::UserDefined(i) => &mut i.nested,
-            ImplSource::Param(n, _) | ImplSource::Builtin(n) => n,
-            ImplSource::Closure(c) => &mut c.nested,
-            ImplSource::Generator(c) => &mut c.nested,
-            ImplSource::Future(c) => &mut c.nested,
+            ImplSource::Param(n, _)
+            | ImplSource::Builtin(n)
+            | ImplSource::FnPointer(n)
+            | ImplSource::Closure(n)
+            | ImplSource::Generator(n)
+            | ImplSource::Future(n) => n,
             ImplSource::Object(d) => &mut d.nested,
-            ImplSource::FnPointer(d) => &mut d.nested,
             ImplSource::TraitAlias(d) => &mut d.nested,
             ImplSource::TraitUpcasting(d) => &mut d.nested,
         }
@@ -739,25 +742,10 @@ impl<'tcx, N> ImplSource<'tcx, N> {
                 vtable_base: o.vtable_base,
                 nested: o.nested.into_iter().map(f).collect(),
             }),
-            ImplSource::Closure(c) => ImplSource::Closure(ImplSourceClosureData {
-                closure_def_id: c.closure_def_id,
-                substs: c.substs,
-                nested: c.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::Generator(c) => ImplSource::Generator(ImplSourceGeneratorData {
-                generator_def_id: c.generator_def_id,
-                substs: c.substs,
-                nested: c.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::Future(c) => ImplSource::Future(ImplSourceFutureData {
-                generator_def_id: c.generator_def_id,
-                substs: c.substs,
-                nested: c.nested.into_iter().map(f).collect(),
-            }),
-            ImplSource::FnPointer(p) => ImplSource::FnPointer(ImplSourceFnPointerData {
-                fn_ty: p.fn_ty,
-                nested: p.nested.into_iter().map(f).collect(),
-            }),
+            ImplSource::Closure(n) => ImplSource::Closure(n.into_iter().map(f).collect()),
+            ImplSource::Generator(n) => ImplSource::Generator(n.into_iter().map(f).collect()),
+            ImplSource::Future(n) => ImplSource::Future(n.into_iter().map(f).collect()),
+            ImplSource::FnPointer(n) => ImplSource::FnPointer(n.into_iter().map(f).collect()),
             ImplSource::TraitAlias(d) => ImplSource::TraitAlias(ImplSourceTraitAliasData {
                 alias_def_id: d.alias_def_id,
                 substs: d.substs,
@@ -793,36 +781,6 @@ pub struct ImplSourceUserDefinedData<'tcx, N> {
 
 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
 #[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceGeneratorData<'tcx, N> {
-    pub generator_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
-    /// Nested obligations. This can be non-empty if the generator
-    /// signature contains associated types.
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceFutureData<'tcx, N> {
-    pub generator_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
-    /// Nested obligations. This can be non-empty if the generator
-    /// signature contains associated types.
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceClosureData<'tcx, N> {
-    pub closure_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
-    /// Nested obligations. This can be non-empty if the closure
-    /// signature contains associated types.
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceTraitUpcastingData<N> {
     /// The vtable is formed by concatenating together the method lists of
     /// the base object trait and all supertraits, pointers to supertrait vtable will
@@ -850,13 +808,6 @@ pub struct ImplSourceObjectData<N> {
 
 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
 #[derive(TypeFoldable, TypeVisitable)]
-pub struct ImplSourceFnPointerData<'tcx, N> {
-    pub fn_ty: Ty<'tcx>,
-    pub nested: Vec<N>,
-}
-
-#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Lift)]
-#[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceTraitAliasData<'tcx, N> {
     pub alias_def_id: DefId,
     pub substs: SubstsRef<'tcx>,
diff --git a/compiler/rustc_middle/src/traits/structural_impls.rs b/compiler/rustc_middle/src/traits/structural_impls.rs
index 3e7ed4dabe9..bc0e656a656 100644
--- a/compiler/rustc_middle/src/traits/structural_impls.rs
+++ b/compiler/rustc_middle/src/traits/structural_impls.rs
@@ -42,36 +42,6 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceUserDefinedData<'tcx,
     }
 }
 
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceGeneratorData<'tcx, N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
-            f,
-            "ImplSourceGeneratorData(generator_def_id={:?}, substs={:?}, nested={:?})",
-            self.generator_def_id, self.substs, self.nested
-        )
-    }
-}
-
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceFutureData<'tcx, N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
-            f,
-            "ImplSourceFutureData(generator_def_id={:?}, substs={:?}, nested={:?})",
-            self.generator_def_id, self.substs, self.nested
-        )
-    }
-}
-
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceClosureData<'tcx, N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
-            f,
-            "ImplSourceClosureData(closure_def_id={:?}, substs={:?}, nested={:?})",
-            self.closure_def_id, self.substs, self.nested
-        )
-    }
-}
-
 impl<N: fmt::Debug> fmt::Debug for traits::ImplSourceTraitUpcastingData<N> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
@@ -92,12 +62,6 @@ impl<N: fmt::Debug> fmt::Debug for traits::ImplSourceObjectData<N> {
     }
 }
 
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceFnPointerData<'tcx, N> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "ImplSourceFnPointerData(fn_ty={:?}, nested={:?})", self.fn_ty, self.nested)
-    }
-}
-
 impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceTraitAliasData<'tcx, N> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index f82885252b7..1477c8957f6 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -3,6 +3,7 @@
 use super::specialization_graph;
 use super::translate_substs;
 use super::util;
+use super::ImplSourceUserDefinedData;
 use super::MismatchedProjectionTypes;
 use super::Obligation;
 use super::ObligationCause;
@@ -10,10 +11,6 @@ use super::PredicateObligation;
 use super::Selection;
 use super::SelectionContext;
 use super::SelectionError;
-use super::{
-    ImplSourceClosureData, ImplSourceFnPointerData, ImplSourceFutureData, ImplSourceGeneratorData,
-    ImplSourceUserDefinedData,
-};
 use super::{Normalized, NormalizedTy, ProjectionCacheEntry, ProjectionCacheKey};
 
 use crate::errors::InherentProjectionNormalizationOverflow;
@@ -2015,9 +2012,14 @@ fn confirm_select_candidate<'cx, 'tcx>(
 fn confirm_generator_candidate<'cx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'tcx>,
     obligation: &ProjectionTyObligation<'tcx>,
-    impl_source: ImplSourceGeneratorData<'tcx, PredicateObligation<'tcx>>,
+    nested: Vec<PredicateObligation<'tcx>>,
 ) -> Progress<'tcx> {
-    let gen_sig = impl_source.substs.as_generator().poly_sig();
+    let ty::Generator(_, substs, _) =
+        selcx.infcx.shallow_resolve(obligation.predicate.self_ty()).kind()
+    else {
+        unreachable!()
+    };
+    let gen_sig = substs.as_generator().poly_sig();
     let Normalized { value: gen_sig, obligations } = normalize_with_depth(
         selcx,
         obligation.param_env,
@@ -2055,16 +2057,21 @@ fn confirm_generator_candidate<'cx, 'tcx>(
     });
 
     confirm_param_env_candidate(selcx, obligation, predicate, false)
-        .with_addl_obligations(impl_source.nested)
+        .with_addl_obligations(nested)
         .with_addl_obligations(obligations)
 }
 
 fn confirm_future_candidate<'cx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'tcx>,
     obligation: &ProjectionTyObligation<'tcx>,
-    impl_source: ImplSourceFutureData<'tcx, PredicateObligation<'tcx>>,
+    nested: Vec<PredicateObligation<'tcx>>,
 ) -> Progress<'tcx> {
-    let gen_sig = impl_source.substs.as_generator().poly_sig();
+    let ty::Generator(_, substs, _) =
+        selcx.infcx.shallow_resolve(obligation.predicate.self_ty()).kind()
+    else {
+        unreachable!()
+    };
+    let gen_sig = substs.as_generator().poly_sig();
     let Normalized { value: gen_sig, obligations } = normalize_with_depth(
         selcx,
         obligation.param_env,
@@ -2094,7 +2101,7 @@ fn confirm_future_candidate<'cx, 'tcx>(
     });
 
     confirm_param_env_candidate(selcx, obligation, predicate, false)
-        .with_addl_obligations(impl_source.nested)
+        .with_addl_obligations(nested)
         .with_addl_obligations(obligations)
 }
 
@@ -2155,9 +2162,9 @@ fn confirm_builtin_candidate<'cx, 'tcx>(
 fn confirm_fn_pointer_candidate<'cx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'tcx>,
     obligation: &ProjectionTyObligation<'tcx>,
-    fn_pointer_impl_source: ImplSourceFnPointerData<'tcx, PredicateObligation<'tcx>>,
+    nested: Vec<PredicateObligation<'tcx>>,
 ) -> Progress<'tcx> {
-    let fn_type = selcx.infcx.shallow_resolve(fn_pointer_impl_source.fn_ty);
+    let fn_type = selcx.infcx.shallow_resolve(obligation.predicate.self_ty());
     let sig = fn_type.fn_sig(selcx.tcx());
     let Normalized { value: sig, obligations } = normalize_with_depth(
         selcx,
@@ -2168,16 +2175,21 @@ fn confirm_fn_pointer_candidate<'cx, 'tcx>(
     );
 
     confirm_callable_candidate(selcx, obligation, sig, util::TupleArgumentsFlag::Yes)
-        .with_addl_obligations(fn_pointer_impl_source.nested)
+        .with_addl_obligations(nested)
         .with_addl_obligations(obligations)
 }
 
 fn confirm_closure_candidate<'cx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'tcx>,
     obligation: &ProjectionTyObligation<'tcx>,
-    impl_source: ImplSourceClosureData<'tcx, PredicateObligation<'tcx>>,
+    nested: Vec<PredicateObligation<'tcx>>,
 ) -> Progress<'tcx> {
-    let closure_sig = impl_source.substs.as_closure().sig();
+    let ty::Closure(_, substs) =
+        selcx.infcx.shallow_resolve(obligation.predicate.self_ty()).kind()
+    else {
+        unreachable!()
+    };
+    let closure_sig = substs.as_closure().sig();
     let Normalized { value: closure_sig, obligations } = normalize_with_depth(
         selcx,
         obligation.param_env,
@@ -2189,7 +2201,7 @@ fn confirm_closure_candidate<'cx, 'tcx>(
     debug!(?obligation, ?closure_sig, ?obligations, "confirm_closure_candidate");
 
     confirm_callable_candidate(selcx, obligation, closure_sig, util::TupleArgumentsFlag::No)
-        .with_addl_obligations(impl_source.nested)
+        .with_addl_obligations(nested)
         .with_addl_obligations(obligations)
 }
 
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index bf37cc68b8c..d369a087c9b 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -27,7 +27,6 @@ use crate::traits::vtable::{
 };
 use crate::traits::{
     BuiltinDerivedObligation, ImplDerivedObligation, ImplDerivedObligationCause, ImplSource,
-    ImplSourceClosureData, ImplSourceFnPointerData, ImplSourceFutureData, ImplSourceGeneratorData,
     ImplSourceObjectData, ImplSourceTraitAliasData, ImplSourceTraitUpcastingData,
     ImplSourceUserDefinedData, Normalized, Obligation, ObligationCause,
     OutputTypeParameterMismatch, PredicateObligation, Selection, SelectionError,
@@ -664,8 +663,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         &mut self,
         obligation: &TraitObligation<'tcx>,
         is_const: bool,
-    ) -> Result<ImplSourceFnPointerData<'tcx, PredicateObligation<'tcx>>, SelectionError<'tcx>>
-    {
+    ) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
         debug!(?obligation, "confirm_fn_pointer_candidate");
 
         let tcx = self.tcx();
@@ -717,7 +715,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let tr = ty::TraitRef::from_lang_item(self.tcx(), LangItem::Sized, cause.span, [output_ty]);
         nested.push(Obligation::new(self.infcx.tcx, cause, obligation.param_env, tr));
 
-        Ok(ImplSourceFnPointerData { fn_ty: self_ty, nested })
+        Ok(nested)
     }
 
     fn confirm_trait_alias_candidate(
@@ -749,8 +747,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     fn confirm_generator_candidate(
         &mut self,
         obligation: &TraitObligation<'tcx>,
-    ) -> Result<ImplSourceGeneratorData<'tcx, PredicateObligation<'tcx>>, SelectionError<'tcx>>
-    {
+    ) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
         // Okay to skip binder because the substs on generator types never
         // touch bound regions, they just capture the in-scope
         // type/region parameters.
@@ -783,13 +780,13 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
         debug!(?trait_ref, ?nested, "generator candidate obligations");
 
-        Ok(ImplSourceGeneratorData { generator_def_id, substs, nested })
+        Ok(nested)
     }
 
     fn confirm_future_candidate(
         &mut self,
         obligation: &TraitObligation<'tcx>,
-    ) -> Result<ImplSourceFutureData<'tcx, PredicateObligation<'tcx>>, SelectionError<'tcx>> {
+    ) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
         // Okay to skip binder because the substs on generator types never
         // touch bound regions, they just capture the in-scope
         // type/region parameters.
@@ -813,14 +810,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
         debug!(?trait_ref, ?nested, "future candidate obligations");
 
-        Ok(ImplSourceFutureData { generator_def_id, substs, nested })
+        Ok(nested)
     }
 
     #[instrument(skip(self), level = "debug")]
     fn confirm_closure_candidate(
         &mut self,
         obligation: &TraitObligation<'tcx>,
-    ) -> Result<ImplSourceClosureData<'tcx, PredicateObligation<'tcx>>, SelectionError<'tcx>> {
+    ) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
         let kind = self
             .tcx()
             .fn_trait_kind_from_def_id(obligation.predicate.def_id())
@@ -847,7 +844,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             ));
         }
 
-        Ok(ImplSourceClosureData { closure_def_id, substs, nested })
+        Ok(nested)
     }
 
     /// In the case of closure types and fn pointers,
diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs
index 81ad883903f..cc7700f378a 100644
--- a/compiler/rustc_ty_utils/src/instance.rs
+++ b/compiler/rustc_ty_utils/src/instance.rs
@@ -177,30 +177,30 @@ fn resolve_associated_item<'tcx>(
 
             Some(ty::Instance::new(leaf_def.item.def_id, substs))
         }
-        traits::ImplSource::Generator(generator_data) => {
+        traits::ImplSource::Generator(_) => {
+            let ty::Generator(generator_def_id, substs, _) = *rcvr_substs.type_at(0).kind() else {
+                unreachable!()
+            };
             if cfg!(debug_assertions) && tcx.item_name(trait_item_id) != sym::resume {
                 // For compiler developers who'd like to add new items to `Generator`,
                 // you either need to generate a shim body, or perhaps return
                 // `InstanceDef::Item` pointing to a trait default method body if
                 // it is given a default implementation by the trait.
                 span_bug!(
-                    tcx.def_span(generator_data.generator_def_id),
+                    tcx.def_span(generator_def_id),
                     "no definition for `{trait_ref}::{}` for built-in generator type",
                     tcx.item_name(trait_item_id)
                 )
             }
-            Some(Instance {
-                def: ty::InstanceDef::Item(generator_data.generator_def_id),
-                substs: generator_data.substs,
-            })
+            Some(Instance { def: ty::InstanceDef::Item(generator_def_id), substs })
         }
-        traits::ImplSource::Future(future_data) => {
+        traits::ImplSource::Future(_) => {
+            let ty::Generator(generator_def_id, substs, _) = *rcvr_substs.type_at(0).kind() else {
+                unreachable!()
+            };
             if Some(trait_item_id) == tcx.lang_items().future_poll_fn() {
                 // `Future::poll` is generated by the compiler.
-                Some(Instance {
-                    def: ty::InstanceDef::Item(future_data.generator_def_id),
-                    substs: future_data.substs,
-                })
+                Some(Instance { def: ty::InstanceDef::Item(generator_def_id), substs: substs })
             } else {
                 // All other methods are default methods of the `Future` trait.
                 // (this assumes that `ImplSource::Future` is only used for methods on `Future`)
@@ -208,7 +208,10 @@ fn resolve_associated_item<'tcx>(
                 Some(Instance::new(trait_item_id, rcvr_substs))
             }
         }
-        traits::ImplSource::Closure(closure_data) => {
+        traits::ImplSource::Closure(_) => {
+            let ty::Closure(closure_def_id, substs) = *rcvr_substs.type_at(0).kind() else {
+                unreachable!()
+            };
             if cfg!(debug_assertions)
                 && ![sym::call, sym::call_mut, sym::call_once]
                     .contains(&tcx.item_name(trait_item_id))
@@ -218,20 +221,15 @@ fn resolve_associated_item<'tcx>(
                 // `InstanceDef::Item` pointing to a trait default method body if
                 // it is given a default implementation by the trait.
                 span_bug!(
-                    tcx.def_span(closure_data.closure_def_id),
+                    tcx.def_span(closure_def_id),
                     "no definition for `{trait_ref}::{}` for built-in closure type",
                     tcx.item_name(trait_item_id)
                 )
             }
             let trait_closure_kind = tcx.fn_trait_kind_from_def_id(trait_id).unwrap();
-            Instance::resolve_closure(
-                tcx,
-                closure_data.closure_def_id,
-                closure_data.substs,
-                trait_closure_kind,
-            )
+            Instance::resolve_closure(tcx, closure_def_id, substs, trait_closure_kind)
         }
-        traits::ImplSource::FnPointer(ref data) => match data.fn_ty.kind() {
+        traits::ImplSource::FnPointer(_) => match rcvr_substs.type_at(0).kind() {
             ty::FnDef(..) | ty::FnPtr(..) => {
                 if cfg!(debug_assertions)
                     && ![sym::call, sym::call_mut, sym::call_once]
@@ -247,7 +245,7 @@ fn resolve_associated_item<'tcx>(
                     )
                 }
                 Some(Instance {
-                    def: ty::InstanceDef::FnPtrShim(trait_item_id, data.fn_ty),
+                    def: ty::InstanceDef::FnPtrShim(trait_item_id, rcvr_substs.type_at(0)),
                     substs: rcvr_substs,
                 })
             }