Begin to implement type system layer of unsafe binders

compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs

@@ -545,6 +545,7 @@ where
             | ty::Ref(_, _, _)
             | ty::FnDef(_, _)
             | ty::FnPtr(..)
+            | ty::UnsafeBinder(_)
             | ty::Dynamic(..)
             | ty::Closure(..)
             | ty::CoroutineClosure(..)
@@ -634,6 +635,7 @@ where
             | ty::Ref(_, _, _)
             | ty::FnDef(_, _)
             | ty::FnPtr(..)
+            | ty::UnsafeBinder(_)
             | ty::Alias(..)
             | ty::Closure(..)
             | ty::CoroutineClosure(..)

compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs

@@ -83,6 +83,8 @@ where
             .map(|bty| bty.instantiate(cx, args))
             .collect()),
 
+        ty::UnsafeBinder(bound_ty) => Ok(vec![bound_ty.into()]),
+
         // For `PhantomData<T>`, we pass `T`.
         ty::Adt(def, args) if def.is_phantom_data() => Ok(vec![ty::Binder::dummy(args.type_at(0))]),
 
@@ -144,6 +146,8 @@ where
             panic!("unexpected type `{ty:?}`")
         }
 
+        ty::UnsafeBinder(bound_ty) => Ok(vec![bound_ty.into()]),
+
         // impl Sized for ()
         // impl Sized for (T1, T2, .., Tn) where Tn: Sized if n >= 1
         ty::Tuple(tys) => Ok(tys.last().map_or_else(Vec::new, |ty| vec![ty::Binder::dummy(ty)])),
@@ -239,6 +243,8 @@ where
             }
         },
 
+        ty::UnsafeBinder(_) => Err(NoSolution),
+
         // impl Copy/Clone for CoroutineWitness where T: Copy/Clone forall T in coroutine_hidden_types
         ty::CoroutineWitness(def_id, args) => Ok(ecx
             .cx()
@@ -374,6 +380,7 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_callable<I: Intern
         | ty::Never
         | ty::Tuple(_)
         | ty::Pat(_, _)
+        | ty::UnsafeBinder(_)
         | ty::Alias(_, _)
         | ty::Param(_)
         | ty::Placeholder(..)
@@ -544,6 +551,7 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_async_callable<I:
         | ty::Coroutine(_, _)
         | ty::CoroutineWitness(..)
         | ty::Never
+        | ty::UnsafeBinder(_)
         | ty::Tuple(_)
         | ty::Alias(_, _)
         | ty::Param(_)
@@ -694,7 +702,8 @@ pub(in crate::solve) fn extract_fn_def_from_const_callable<I: Interner>(
         | ty::Param(_)
         | ty::Placeholder(..)
         | ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
-        | ty::Error(_) => return Err(NoSolution),
+        | ty::Error(_)
+        | ty::UnsafeBinder(_) => return Err(NoSolution),
 
         ty::Bound(..)
         | ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
@@ -764,6 +773,10 @@ pub(in crate::solve) fn const_conditions_for_destruct<I: Interner>(
         | ty::Coroutine(_, _)
         | ty::CoroutineWitness(_, _) => Err(NoSolution),
 
+        // FIXME(unsafe_binders): Unsafe binders could implement `~const Drop`
+        // if their inner type implements it.
+        ty::UnsafeBinder(_) => Err(NoSolution),
+
         ty::Dynamic(..) | ty::Param(_) | ty::Alias(..) | ty::Placeholder(_) | ty::Foreign(_) => {
             Err(NoSolution)
         }

compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs

@@ -619,6 +619,11 @@ where
                     Some(tail_ty) => Ty::new_projection(cx, metadata_def_id, [tail_ty]),
                 },
 
+                ty::UnsafeBinder(_) => {
+                    // FIXME(unsafe_binder): Figure out how to handle pointee for unsafe binders.
+                    todo!()
+                }
+
                 ty::Infer(
                     ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_),
                 )
@@ -822,6 +827,11 @@ where
             | ty::Tuple(_)
             | ty::Error(_) => self_ty.discriminant_ty(ecx.cx()),
 
+            ty::UnsafeBinder(_) => {
+                // FIXME(unsafe_binders): instantiate this with placeholders?? i guess??
+                todo!("discr subgoal...")
+            }
+
             // We do not call `Ty::discriminant_ty` on alias, param, or placeholder
             // types, which return `<self_ty as DiscriminantKind>::Discriminant`
             // (or ICE in the case of placeholders). Projecting a type to itself
@@ -869,6 +879,11 @@ where
             | ty::Tuple(_)
             | ty::Error(_) => self_ty.async_destructor_ty(ecx.cx()),
 
+            ty::UnsafeBinder(_) => {
+                // FIXME(unsafe_binders): Instantiate the binder with placeholders I guess.
+                todo!()
+            }
+
             // We do not call `Ty::async_destructor_ty` on alias, param, or placeholder
             // types, which return `<self_ty as AsyncDestruct>::AsyncDestructor`
             // (or ICE in the case of placeholders). Projecting a type to itself

compiler/rustc_next_trait_solver/src/solve/trait_goals.rs

@@ -1100,7 +1100,8 @@ where
             | ty::CoroutineWitness(..)
             | ty::Never
             | ty::Tuple(_)
-            | ty::Adt(_, _) => {
+            | ty::Adt(_, _)
+            | ty::UnsafeBinder(_) => {
                 let mut disqualifying_impl = None;
                 self.cx().for_each_relevant_impl(
                     goal.predicate.def_id(),