Add built-in const impls for Clone and Copy

Author: fee1-dead

compiler/rustc_next_trait_solver/src/solve/effect_goals.rs

@@ -211,10 +211,32 @@ where
     }
 
     fn consider_builtin_copy_clone_candidate(
-        _ecx: &mut EvalCtxt<'_, D>,
-        _goal: Goal<I, Self>,
+        ecx: &mut EvalCtxt<'_, D>,
+        goal: Goal<I, Self>,
     ) -> Result<Candidate<I>, NoSolution> {
-        Err(NoSolution)
+        let cx = ecx.cx();
+
+        let self_ty = goal.predicate.self_ty();
+        let constituent_tys =
+            structural_traits::instantiate_constituent_tys_for_copy_clone_trait(ecx, self_ty)?;
+
+        ecx.probe_builtin_trait_candidate(BuiltinImplSource::Misc).enter(|ecx| {
+            ecx.enter_forall(constituent_tys, |ecx, tys| {
+                ecx.add_goals(
+                    GoalSource::ImplWhereBound,
+                    tys.into_iter().map(|ty| {
+                        goal.with(
+                            cx,
+                            ty::ClauseKind::HostEffect(
+                                goal.predicate.with_replaced_self_ty(cx, ty),
+                            ),
+                        )
+                    }),
+                );
+            });
+
+            ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+        })
     }
 
     fn consider_builtin_fn_ptr_trait_candidate(

compiler/rustc_trait_selection/src/traits/effects.rs

@@ -8,7 +8,7 @@ use rustc_middle::span_bug;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::ty::elaborate::elaborate;
 use rustc_middle::ty::fast_reject::DeepRejectCtxt;
-use rustc_middle::ty::{self, TypingMode};
+use rustc_middle::ty::{self, Ty, TypingMode};
 use thin_vec::{ThinVec, thin_vec};
 
 use super::SelectionContext;
@@ -303,6 +303,9 @@ fn evaluate_host_effect_from_builtin_impls<'tcx>(
     obligation: &HostEffectObligation<'tcx>,
 ) -> Result<ThinVec<PredicateObligation<'tcx>>, EvaluationFailure> {
     match selcx.tcx().as_lang_item(obligation.predicate.def_id()) {
+        Some(LangItem::Copy | LangItem::Clone) => {
+            evaluate_host_effect_for_copy_clone_goal(selcx, obligation)
+        }
         Some(LangItem::Destruct) => evaluate_host_effect_for_destruct_goal(selcx, obligation),
         Some(LangItem::Fn | LangItem::FnMut | LangItem::FnOnce) => {
             evaluate_host_effect_for_fn_goal(selcx, obligation)
@@ -311,6 +314,95 @@ fn evaluate_host_effect_from_builtin_impls<'tcx>(
     }
 }
 
+fn evaluate_host_effect_for_copy_clone_goal<'tcx>(
+    selcx: &mut SelectionContext<'_, 'tcx>,
+    obligation: &HostEffectObligation<'tcx>,
+) -> Result<ThinVec<PredicateObligation<'tcx>>, EvaluationFailure> {
+    let tcx = selcx.tcx();
+    let self_ty = obligation.predicate.self_ty();
+    let constituent_tys = match *self_ty.kind() {
+        // impl Copy/Clone for FnDef, FnPtr
+        ty::FnDef(..) | ty::FnPtr(..) | ty::Error(_) => Ok(ty::Binder::dummy(vec![])),
+
+        // Implementations are provided in core
+        ty::Uint(_)
+        | ty::Int(_)
+        | ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
+        | ty::Bool
+        | ty::Float(_)
+        | ty::Char
+        | ty::RawPtr(..)
+        | ty::Never
+        | ty::Ref(_, _, ty::Mutability::Not)
+        | ty::Array(..) => Err(EvaluationFailure::NoSolution),
+
+        // Cannot implement in core, as we can't be generic over patterns yet,
+        // so we'd have to list all patterns and type combinations.
+        ty::Pat(ty, ..) => Ok(ty::Binder::dummy(vec![ty])),
+
+        ty::Dynamic(..)
+        | ty::Str
+        | ty::Slice(_)
+        | ty::Foreign(..)
+        | ty::Ref(_, _, ty::Mutability::Mut)
+        | ty::Adt(_, _)
+        | ty::Alias(_, _)
+        | ty::Param(_)
+        | ty::Placeholder(..) => Err(EvaluationFailure::NoSolution),
+
+        ty::Bound(..)
+        | ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
+            panic!("unexpected type `{self_ty:?}`")
+        }
+
+        // impl Copy/Clone for (T1, T2, .., Tn) where T1: Copy/Clone, T2: Copy/Clone, .. Tn: Copy/Clone
+        ty::Tuple(tys) => Ok(ty::Binder::dummy(tys.to_vec())),
+
+        // impl Copy/Clone for Closure where Self::TupledUpvars: Copy/Clone
+        ty::Closure(_, args) => Ok(ty::Binder::dummy(vec![args.as_closure().tupled_upvars_ty()])),
+
+        // impl Copy/Clone for CoroutineClosure where Self::TupledUpvars: Copy/Clone
+        ty::CoroutineClosure(_, args) => {
+            Ok(ty::Binder::dummy(vec![args.as_coroutine_closure().tupled_upvars_ty()]))
+        }
+
+        // only when `coroutine_clone` is enabled and the coroutine is movable
+        // impl Copy/Clone for Coroutine where T: Copy/Clone forall T in (upvars, witnesses)
+        ty::Coroutine(def_id, args) => match tcx.coroutine_movability(def_id) {
+            ty::Movability::Static => Err(EvaluationFailure::NoSolution),
+            ty::Movability::Movable => {
+                if tcx.features().coroutine_clone() {
+                    Ok(ty::Binder::dummy(vec![
+                        args.as_coroutine().tupled_upvars_ty(),
+                        Ty::new_coroutine_witness_for_coroutine(tcx, def_id, args),
+                    ]))
+                } else {
+                    Err(EvaluationFailure::NoSolution)
+                }
+            }
+        },
+
+        ty::UnsafeBinder(_) => Err(EvaluationFailure::NoSolution),
+
+        // impl Copy/Clone for CoroutineWitness where T: Copy/Clone forall T in coroutine_hidden_types
+        ty::CoroutineWitness(def_id, args) => Ok(tcx
+            .coroutine_hidden_types(def_id)
+            .instantiate(tcx, args)
+            .map_bound(|bound| bound.types.to_vec())),
+    }?;
+
+    Ok(constituent_tys
+        .iter()
+        .map(|ty| {
+            obligation.with(
+                tcx,
+                ty.map_bound(|ty| ty::TraitRef::new(tcx, obligation.predicate.def_id(), [ty]))
+                    .to_host_effect_clause(tcx, obligation.predicate.constness),
+            )
+        })
+        .collect())
+}
+
 // NOTE: Keep this in sync with `const_conditions_for_destruct` in the new solver.
 fn evaluate_host_effect_for_destruct_goal<'tcx>(
     selcx: &mut SelectionContext<'_, 'tcx>,

compiler/rustc_type_ir/src/predicate.rs

@@ -121,7 +121,7 @@ impl<I: Interner> ty::Binder<I, TraitRef<I>> {
     }
 
     pub fn to_host_effect_clause(self, cx: I, constness: BoundConstness) -> I::Clause {
-        self.map_bound(|trait_ref| {
+        self.map_bound(|trait_ref: TraitRef<I>| {
             ty::ClauseKind::HostEffect(HostEffectPredicate { trait_ref, constness })
         })
         .upcast(cx)

tests/ui/traits/const-traits/const-traits-alloc.rs

@@ -1,4 +1,4 @@
-//@ run-pass
+//@ check-pass
 #![feature(const_trait_impl, const_default)]
 #![allow(dead_code)]
 // alloc::string

tests/ui/traits/const-traits/const-traits-core.rs

@@ -1,6 +1,13 @@
-//@ run-pass
+//@ check-pass
 #![feature(
-    const_trait_impl, const_default, ptr_alignment_type, ascii_char, f16, f128, sync_unsafe_cell,
+    const_clone,
+    const_default,
+    const_trait_impl,
+    ptr_alignment_type,
+    ascii_char,
+    f16,
+    f128,
+    sync_unsafe_cell,
 )]
 #![allow(dead_code)]
 // core::default
@@ -43,4 +50,8 @@ const REF_CELL: std::cell::RefCell<()> = Default::default();
 const UNSAFE_CELL: std::cell::UnsafeCell<()> = Default::default();
 const SYNC_UNSAFE_CELL: std::cell::SyncUnsafeCell<()> = Default::default();
 
+// `Clone` for tuples
+const BUILTIN_CLONE: () = ().clone();
+const BUILTIN_CLONE_2: (u32, i32) = (42, 100).clone();
+
 fn main() {}