Remove even more redundant builtin candidates

1 files changed, 60 insertions, 77 deletions

diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs
index cc7700f378a..45b1075b602 100644
--- a/compiler/rustc_ty_utils/src/instance.rs
+++ b/compiler/rustc_ty_utils/src/instance.rs
@@ -177,83 +177,6 @@ fn resolve_associated_item<'tcx>(
 
             Some(ty::Instance::new(leaf_def.item.def_id, substs))
         }
-        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_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_def_id), substs })
-        }
-        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(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`)
-                debug_assert!(tcx.defaultness(trait_item_id).has_value());
-                Some(Instance::new(trait_item_id, rcvr_substs))
-            }
-        }
-        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))
-            {
-                // For compiler developers who'd like to add new items to `Fn`/`FnMut`/`FnOnce`,
-                // 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(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_def_id, substs, trait_closure_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]
-                        .contains(&tcx.item_name(trait_item_id))
-                {
-                    // For compiler developers who'd like to add new items to `Fn`/`FnMut`/`FnOnce`,
-                    // 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.
-                    bug!(
-                        "no definition for `{trait_ref}::{}` for built-in fn type",
-                        tcx.item_name(trait_item_id)
-                    )
-                }
-                Some(Instance {
-                    def: ty::InstanceDef::FnPtrShim(trait_item_id, rcvr_substs.type_at(0)),
-                    substs: rcvr_substs,
-                })
-            }
-            _ => bug!(
-                "no built-in definition for `{trait_ref}::{}` for non-fn type",
-                tcx.item_name(trait_item_id)
-            ),
-        },
         traits::ImplSource::Object(ref data) => {
             traits::get_vtable_index_of_object_method(tcx, data, trait_item_id).map(|index| {
                 Instance {
@@ -306,6 +229,66 @@ fn resolve_associated_item<'tcx>(
                         span: tcx.def_span(trait_item_id),
                     })
                 }
+            } else if Some(trait_ref.def_id) == lang_items.future_trait() {
+                let ty::Generator(generator_def_id, substs, _) = *rcvr_substs.type_at(0).kind() else {
+                    bug!()
+                };
+                if Some(trait_item_id) == tcx.lang_items().future_poll_fn() {
+                    // `Future::poll` is generated by the compiler.
+                    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::Builtin` is only used for methods on `Future`)
+                    debug_assert!(tcx.defaultness(trait_item_id).has_value());
+                    Some(Instance::new(trait_item_id, rcvr_substs))
+                }
+            } else if Some(trait_ref.def_id) == lang_items.gen_trait() {
+                let ty::Generator(generator_def_id, substs, _) = *rcvr_substs.type_at(0).kind() else {
+                    bug!()
+                };
+                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_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_def_id), substs })
+            } else if tcx.fn_trait_kind_from_def_id(trait_ref.def_id).is_some() {
+                // FIXME: This doesn't check for malformed libcore that defines, e.g.,
+                // `trait Fn { fn call_once(&self) { .. } }`. This is mostly for extension
+                // methods.
+                if cfg!(debug_assertions)
+                    && ![sym::call, sym::call_mut, sym::call_once]
+                        .contains(&tcx.item_name(trait_item_id))
+                {
+                    // For compiler developers who'd like to add new items to `Fn`/`FnMut`/`FnOnce`,
+                    // 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.
+                    bug!(
+                        "no definition for `{trait_ref}::{}` for built-in callable type",
+                        tcx.item_name(trait_item_id)
+                    )
+                }
+                match *rcvr_substs.type_at(0).kind() {
+                    ty::Closure(closure_def_id, substs) => {
+                        let trait_closure_kind = tcx.fn_trait_kind_from_def_id(trait_id).unwrap();
+                        Instance::resolve_closure(tcx, closure_def_id, substs, trait_closure_kind)
+                    }
+                    ty::FnDef(..) | ty::FnPtr(..) => Some(Instance {
+                        def: ty::InstanceDef::FnPtrShim(trait_item_id, rcvr_substs.type_at(0)),
+                        substs: rcvr_substs,
+                    }),
+                    _ => bug!(
+                        "no built-in definition for `{trait_ref}::{}` for non-fn type",
+                        tcx.item_name(trait_item_id)
+                    ),
+                }
             } else {
                 None
             }