Add empty ConstKind::Abstract

[rust.git] / compiler / rustc_trait_selection / src / traits / object_safety.rs

diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs
index eaca3eaef0c1fa5f6c2a769a4573283398cc31ae..bc8abc0eb9036949c6e16fc979be97aadba74459 100644 (file)
--- a/compiler/rustc_trait_selection/src/traits/object_safety.rs
+++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs
@@ -17,11 +17,10 @@
 use rustc_errors::{DelayDm, FatalError, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-use rustc_middle::ty::abstract_const::{walk_abstract_const, AbstractConst};
+use rustc_middle::ty::subst::{GenericArg, InternalSubsts};
 use rustc_middle::ty::{
     self, EarlyBinder, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
 };
-use rustc_middle::ty::{GenericArg, InternalSubsts};
 use rustc_middle::ty::{Predicate, ToPredicate};
 use rustc_session::lint::builtin::WHERE_CLAUSES_OBJECT_SAFETY;
 use rustc_span::symbol::Symbol;
@@ -319,6 +318,7 @@ fn predicate_references_self<'tcx>(
         | ty::PredicateKind::Coerce(..)
         | ty::PredicateKind::ConstEvaluatable(..)
         | ty::PredicateKind::ConstEquate(..)
+        | ty::PredicateKind::Ambiguous
         | ty::PredicateKind::TypeWellFormedFromEnv(..) => None,
     }
 }
@@ -350,6 +350,7 @@ fn generics_require_sized_self(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
             | ty::PredicateKind::TypeOutlives(..)
             | ty::PredicateKind::ConstEvaluatable(..)
             | ty::PredicateKind::ConstEquate(..)
+            | ty::PredicateKind::Ambiguous
             | ty::PredicateKind::TypeWellFormedFromEnv(..) => false,
         }
     })
@@ -375,6 +376,7 @@ fn object_safety_violation_for_method(
         let span = match (&v, node) {
             (MethodViolationCode::ReferencesSelfInput(Some(span)), _) => *span,
             (MethodViolationCode::UndispatchableReceiver(Some(span)), _) => *span,
+            (MethodViolationCode::ReferencesImplTraitInTrait(span), _) => *span,
             (MethodViolationCode::ReferencesSelfOutput, Some(node)) => {
                 node.fn_decl().map_or(method.ident(tcx).span, |decl| decl.output.span())
             }
@@ -437,8 +439,8 @@ fn virtual_call_violation_for_method<'tcx>(
     if contains_illegal_self_type_reference(tcx, trait_def_id, sig.output()) {
         return Some(MethodViolationCode::ReferencesSelfOutput);
     }
-    if contains_illegal_impl_trait_in_trait(tcx, sig.output()) {
-        return Some(MethodViolationCode::ReferencesImplTraitInTrait);
+    if let Some(code) = contains_illegal_impl_trait_in_trait(tcx, method.def_id, sig.output()) {
+        return Some(code);
     }
 
     // We can't monomorphize things like `fn foo<A>(...)`.
@@ -684,10 +686,9 @@ fn receiver_is_dispatchable<'tcx>(
         let param_env = tcx.param_env(method.def_id);
 
         // Self: Unsize<U>
-        let unsize_predicate = ty::Binder::dummy(ty::TraitRef {
-            def_id: unsize_did,
-            substs: tcx.mk_substs_trait(tcx.types.self_param, &[unsized_self_ty.into()]),
-        })
+        let unsize_predicate = ty::Binder::dummy(
+            tcx.mk_trait_ref(unsize_did, [tcx.types.self_param, unsized_self_ty]),
+        )
         .without_const()
         .to_predicate(tcx);
 
@@ -719,10 +720,9 @@ fn receiver_is_dispatchable<'tcx>(
 
     // Receiver: DispatchFromDyn<Receiver[Self => U]>
     let obligation = {
-        let predicate = ty::Binder::dummy(ty::TraitRef {
-            def_id: dispatch_from_dyn_did,
-            substs: tcx.mk_substs_trait(receiver_ty, &[unsized_receiver_ty.into()]),
-        })
+        let predicate = ty::Binder::dummy(
+            tcx.mk_trait_ref(dispatch_from_dyn_did, [receiver_ty, unsized_receiver_ty]),
+        )
         .without_const();
 
         Obligation::new(tcx, ObligationCause::dummy(), param_env, predicate)
@@ -842,15 +842,19 @@ fn visit_const(&mut self, ct: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
             //
             // If `AbstractConst::from_const` returned an error we already failed compilation
             // so we don't have to emit an additional error here.
-            use rustc_middle::ty::abstract_const::Node;
-            if let Ok(Some(ct)) = AbstractConst::from_const(self.tcx, ct) {
-                walk_abstract_const(self.tcx, ct, |node| match node.root(self.tcx) {
-                    Node::Leaf(leaf) => self.visit_const(leaf),
-                    Node::Cast(_, _, ty) => self.visit_ty(ty),
-                    Node::Binop(..) | Node::UnaryOp(..) | Node::FunctionCall(_, _) => {
-                        ControlFlow::CONTINUE
-                    }
-                })
+            //
+            // We currently recurse into abstract consts here but do not recurse in
+            // `is_const_evaluatable`. This means that the object safety check is more
+            // liberal than the const eval check.
+            //
+            // This shouldn't really matter though as we can't really use any
+            // constants which are not considered const evaluatable.
+            if let ty::ConstKind::Unevaluated(uv) = ct.kind() &&
+                let Ok(Some(ct)) = self
+                .tcx
+                .expand_bound_abstract_const(self.tcx.bound_abstract_const(uv.def), uv.substs)
+            {
+                self.visit_const(ct)
             } else {
                 ct.super_visit_with(self)
             }
@@ -864,16 +868,24 @@ fn visit_const(&mut self, ct: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
 
 pub fn contains_illegal_impl_trait_in_trait<'tcx>(
     tcx: TyCtxt<'tcx>,
+    fn_def_id: DefId,
     ty: ty::Binder<'tcx, Ty<'tcx>>,
-) -> bool {
+) -> Option<MethodViolationCode> {
+    // This would be caught below, but rendering the error as a separate
+    // `async-specific` message is better.
+    if tcx.asyncness(fn_def_id).is_async() {
+        return Some(MethodViolationCode::AsyncFn);
+    }
+
     // FIXME(RPITIT): Perhaps we should use a visitor here?
-    ty.skip_binder().walk().any(|arg| {
+    ty.skip_binder().walk().find_map(|arg| {
         if let ty::GenericArgKind::Type(ty) = arg.unpack()
             && let ty::Projection(proj) = ty.kind()
+            && tcx.def_kind(proj.item_def_id) == DefKind::ImplTraitPlaceholder
         {
-            tcx.def_kind(proj.item_def_id) == DefKind::ImplTraitPlaceholder
+            Some(MethodViolationCode::ReferencesImplTraitInTrait(tcx.def_span(proj.item_def_id)))
         } else {
-            false
+            None
         }
     })
 }