Report missing cases of bare_trait_objects

compiler/rustc_ast/src/ast.rs

@@ -1964,7 +1964,7 @@ impl TyKind {
 }
 
 /// Syntax used to declare a trait object.
-#[derive(Clone, Copy, PartialEq, Encodable, Decodable, Debug)]
+#[derive(Clone, Copy, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
 pub enum TraitObjectSyntax {
     Dyn,
     None,

compiler/rustc_ast_lowering/src/lib.rs

@@ -1396,7 +1396,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 if kind != TraitObjectSyntax::Dyn {
                     self.maybe_lint_bare_trait(t.span, t.id, false);
                 }
-                hir::TyKind::TraitObject(bounds, lifetime_bound)
+                hir::TyKind::TraitObject(bounds, lifetime_bound, kind)
             }
             TyKind::ImplTrait(def_node_id, ref bounds) => {
                 let span = t.span;
@@ -2648,6 +2648,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         hir::TyKind::TraitObject(
                             arena_vec![self; principal],
                             self.elided_dyn_bound(span),
+                            TraitObjectSyntax::None,
                         )
                     }
                     _ => hir::TyKind::Path(hir::QPath::Resolved(None, path)),

compiler/rustc_hir/src/hir.rs

@@ -6,7 +6,7 @@ use crate::{itemlikevisit, LangItem};
 
 use rustc_ast::util::parser::ExprPrecedence;
 use rustc_ast::{self as ast, CrateSugar, LlvmAsmDialect};
-use rustc_ast::{Attribute, FloatTy, IntTy, Label, LitKind, StrStyle, UintTy};
+use rustc_ast::{Attribute, FloatTy, IntTy, Label, LitKind, StrStyle, TraitObjectSyntax, UintTy};
 pub use rustc_ast::{BorrowKind, ImplPolarity, IsAuto};
 pub use rustc_ast::{CaptureBy, Movability, Mutability};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
@@ -2327,7 +2327,7 @@ pub enum TyKind<'hir> {
     OpaqueDef(ItemId, &'hir [GenericArg<'hir>]),
     /// A trait object type `Bound1 + Bound2 + Bound3`
     /// where `Bound` is a trait or a lifetime.
-    TraitObject(&'hir [PolyTraitRef<'hir>], Lifetime),
+    TraitObject(&'hir [PolyTraitRef<'hir>], Lifetime, TraitObjectSyntax),
     /// Unused for now.
     Typeof(AnonConst),
     /// `TyKind::Infer` means the type should be inferred instead of it having been

compiler/rustc_hir/src/intravisit.rs

@@ -709,7 +709,7 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty<'v>) {
             visitor.visit_ty(ty);
             visitor.visit_anon_const(length)
         }
-        TyKind::TraitObject(bounds, ref lifetime) => {
+        TyKind::TraitObject(bounds, ref lifetime, _syntax) => {
             for bound in bounds {
                 visitor.visit_poly_trait_ref(bound, TraitBoundModifier::None);
             }

compiler/rustc_hir_pretty/src/lib.rs

@@ -410,7 +410,10 @@ impl<'a> State<'a> {
             }
             hir::TyKind::OpaqueDef(..) => self.s.word("/*impl Trait*/"),
             hir::TyKind::Path(ref qpath) => self.print_qpath(qpath, false),
-            hir::TyKind::TraitObject(bounds, ref lifetime) => {
+            hir::TyKind::TraitObject(bounds, ref lifetime, syntax) => {
+                if syntax == ast::TraitObjectSyntax::Dyn {
+                    self.word_space("dyn");
+                }
                 let mut first = true;
                 for bound in bounds {
                     if first {

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs

@@ -99,7 +99,7 @@ impl Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
                 return;
             }
 
-            hir::TyKind::TraitObject(bounds, _) => {
+            hir::TyKind::TraitObject(bounds, ..) => {
                 for bound in bounds {
                     self.current_index.shift_in(1);
                     self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs

@@ -292,7 +292,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                         );
                     }
                 }
-                TyKind::TraitObject(_, lt) => match lt.name {
+                TyKind::TraitObject(_, lt, _) => match lt.name {
                     LifetimeName::ImplicitObjectLifetimeDefault => {
                         err.span_suggestion_verbose(
                             fn_return.span.shrink_to_hi(),
@@ -498,6 +498,7 @@ impl<'tcx> Visitor<'tcx> for HirTraitObjectVisitor {
         if let TyKind::TraitObject(
             poly_trait_refs,
             Lifetime { name: LifetimeName::ImplicitObjectLifetimeDefault, .. },
+            _,
         ) = t.kind
         {
             for ptr in poly_trait_refs {

compiler/rustc_middle/src/ty/diagnostics.rs

@@ -314,6 +314,7 @@ impl<'v> hir::intravisit::Visitor<'v> for TraitObjectVisitor<'v> {
                         hir::LifetimeName::ImplicitObjectLifetimeDefault | hir::LifetimeName::Static,
                     ..
                 },
+                _,
             ) => {
                 self.0.push(ty);
             }

compiler/rustc_resolve/src/late/lifetimes.rs

@@ -540,7 +540,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                 self.missing_named_lifetime_spots.pop();
                 self.is_in_fn_syntax = was_in_fn_syntax;
             }
-            hir::TyKind::TraitObject(bounds, ref lifetime) => {
+            hir::TyKind::TraitObject(bounds, ref lifetime, _) => {
                 debug!("visit_ty: TraitObject(bounds={:?}, lifetime={:?})", bounds, lifetime);
                 for bound in bounds {
                     self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
@@ -2299,7 +2299,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                     self.outer_index.shift_in(1);
                 }
                 match ty.kind {
-                    hir::TyKind::TraitObject(bounds, ref lifetime) => {
+                    hir::TyKind::TraitObject(bounds, ref lifetime, _) => {
                         for bound in bounds {
                             self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
                         }

compiler/rustc_trait_selection/src/infer.rs

@@ -124,7 +124,7 @@ impl<'tcx> InferCtxtBuilderExt<'tcx> for InferCtxtBuilder<'tcx> {
             DUMMY_SP,
             canonical_key,
             |ref infcx, key, canonical_inference_vars| {
-                let mut fulfill_cx = TraitEngine::new(infcx.tcx);
+                let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
                 let value = operation(infcx, &mut *fulfill_cx, key)?;
                 infcx.make_canonicalized_query_response(
                     canonical_inference_vars,

compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs

@@ -62,7 +62,7 @@ fn scrape_region_constraints<'tcx, R>(
     infcx: &InferCtxt<'_, 'tcx>,
     op: impl FnOnce() -> Fallible<InferOk<'tcx, R>>,
 ) -> Fallible<(R, Option<Rc<QueryRegionConstraints<'tcx>>>)> {
-    let mut fulfill_cx = TraitEngine::new(infcx.tcx);
+    let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
     let dummy_body_id = ObligationCause::dummy().body_id;
 
     // During NLL, we expect that nobody will register region

compiler/rustc_traits/src/dropck_outlives.rs

@@ -75,7 +75,7 @@ fn dropck_outlives<'tcx>(
             // Set used to detect infinite recursion.
             let mut ty_set = FxHashSet::default();
 
-            let mut fulfill_cx = TraitEngine::new(infcx.tcx);
+            let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
 
             let cause = ObligationCause::dummy();
             let mut constraints = DtorckConstraint::empty();

compiler/rustc_typeck/src/astconv/mod.rs

@@ -1608,6 +1608,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
     // the whole path.
     // Will fail except for `T::A` and `Self::A`; i.e., if `qself_ty`/`qself_def` are not a type
     // parameter or `Self`.
+    // NOTE: When this function starts resolving `Trait::AssocTy` successfully
+    // it should also start reportint the `BARE_TRAIT_OBJECTS` lint.
     pub fn associated_path_to_ty(
         &self,
         hir_ref_id: hir::HirId,
@@ -2201,7 +2203,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     Some(ast_ty),
                 ))
             }
-            hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
+            hir::TyKind::TraitObject(ref bounds, ref lifetime, _) => {
                 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime, borrowed)
             }
             hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {

compiler/rustc_typeck/src/check/coercion.rs

@@ -1554,7 +1554,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
         if let hir::FnRetTy::Return(ty) = fn_output {
             // Get the return type.
             if let hir::TyKind::OpaqueDef(..) = ty.kind {
-                let ty = AstConv::ast_ty_to_ty(fcx, ty);
+                let ty = <dyn AstConv<'_>>::ast_ty_to_ty(fcx, ty);
                 // Get the `impl Trait`'s `DefId`.
                 if let ty::Opaque(def_id, _) = ty.kind() {
                     let hir_id = fcx.tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
@@ -1616,7 +1616,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
     fn is_return_ty_unsized(&self, fcx: &FnCtxt<'a, 'tcx>, blk_id: hir::HirId) -> bool {
         if let Some((fn_decl, _)) = fcx.get_fn_decl(blk_id) {
             if let hir::FnRetTy::Return(ty) = fn_decl.output {
-                let ty = AstConv::ast_ty_to_ty(fcx, ty);
+                let ty = <dyn AstConv<'_>>::ast_ty_to_ty(fcx, ty);
                 if let ty::Dynamic(..) = ty.kind() {
                     return true;
                 }

compiler/rustc_typeck/src/check/dropck.rs

@@ -77,7 +77,7 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>(
     tcx.infer_ctxt().enter(|ref infcx| {
         let impl_param_env = tcx.param_env(self_type_did);
         let tcx = infcx.tcx;
-        let mut fulfillment_cx = TraitEngine::new(tcx);
+        let mut fulfillment_cx = <dyn TraitEngine<'_>>::new(tcx);
 
         let named_type = tcx.type_of(self_type_did);
 

compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs

@@ -6,14 +6,15 @@ use crate::check::callee::{self, DeferredCallResolution};
 use crate::check::method::{self, MethodCallee, SelfSource};
 use crate::check::{BreakableCtxt, Diverges, Expectation, FallbackMode, FnCtxt, LocalTy};
 
+use rustc_ast::TraitObjectSyntax;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{Applicability, DiagnosticBuilder, ErrorReported};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
-use rustc_hir::{ExprKind, GenericArg, Node, QPath};
+use rustc_hir::{ExprKind, GenericArg, Node, QPath, TyKind};
 use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
 use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
 use rustc_infer::infer::{InferOk, InferResult};
@@ -26,7 +27,9 @@ use rustc_middle::ty::{
     self, AdtKind, CanonicalUserType, DefIdTree, GenericParamDefKind, ToPolyTraitRef, ToPredicate,
     Ty, UserType,
 };
-use rustc_session::{lint, parse::feature_err};
+use rustc_session::lint;
+use rustc_session::lint::builtin::BARE_TRAIT_OBJECTS;
+use rustc_session::parse::feature_err;
 use rustc_span::source_map::{original_sp, DUMMY_SP};
 use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{self, BytePos, MultiSpan, Span};
@@ -472,7 +475,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     }
 
     pub fn to_ty(&self, ast_t: &hir::Ty<'_>) -> Ty<'tcx> {
-        let t = AstConv::ast_ty_to_ty(self, ast_t);
+        let t = <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_t);
         self.register_wf_obligation(t.into(), ast_t.span, traits::MiscObligation);
         t
     }
@@ -854,7 +857,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         // out unconstrained or ambiguous, as we're
                         // just trying to get hints here.
                         self.save_and_restore_in_snapshot_flag(|_| {
-                            let mut fulfill = TraitEngine::new(self.tcx);
+                            let mut fulfill = <dyn TraitEngine<'_>>::new(self.tcx);
                             for obligation in ok.obligations {
                                 fulfill.register_predicate_obligation(self, obligation);
                             }
@@ -947,6 +950,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             result
         });
 
+        if result.is_ok() {
+            self.maybe_lint_bare_trait(qpath, hir_id);
+        }
+
         // Write back the new resolution.
         self.write_resolution(hir_id, result);
         (
@@ -956,6 +963,29 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         )
     }
 
+    fn maybe_lint_bare_trait(&self, qpath: &QPath<'_>, hir_id: hir::HirId) {
+        if let QPath::TypeRelative(self_ty, _) = qpath {
+            if let TyKind::TraitObject([poly_trait_ref, ..], _, TraitObjectSyntax::None) =
+                self_ty.kind
+            {
+                self.tcx.struct_span_lint_hir(BARE_TRAIT_OBJECTS, hir_id, self_ty.span, |lint| {
+                    let mut db = lint
+                        .build(&format!("trait objects without an explicit `dyn` are deprecated"));
+                    let (sugg, app) = match self.tcx.sess.source_map().span_to_snippet(self_ty.span)
+                    {
+                        Ok(s) if poly_trait_ref.trait_ref.path.is_global() => {
+                            (format!("<dyn ({})>", s), Applicability::MachineApplicable)
+                        }
+                        Ok(s) => (format!("<dyn {}>", s), Applicability::MachineApplicable),
+                        Err(_) => ("<dyn <type>>".to_string(), Applicability::HasPlaceholders),
+                    };
+                    db.span_suggestion(self_ty.span, "use `dyn`", sugg, app);
+                    db.emit()
+                });
+            }
+        }
+    }
+
     /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
     pub(in super::super) fn get_node_fn_decl(
         &self,
@@ -1174,9 +1204,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let path_segs = match res {
             Res::Local(_) | Res::SelfCtor(_) => vec![],
-            Res::Def(kind, def_id) => {
-                AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id)
-            }
+            Res::Def(kind, def_id) => <dyn AstConv<'_>>::def_ids_for_value_path_segments(
+                self, segments, self_ty, kind, def_id,
+            ),
             _ => bug!("instantiate_value_path on {:?}", res),
         };
 
@@ -1219,7 +1249,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // errors if type parameters are provided in an inappropriate place.
 
         let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
-        let generics_has_err = AstConv::prohibit_generics(
+        let generics_has_err = <dyn AstConv<'_>>::prohibit_generics(
             self,
             segments.iter().enumerate().filter_map(|(index, seg)| {
                 if !generic_segs.contains(&index) || is_alias_variant_ctor {
@@ -1262,7 +1292,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             if let GenericArgCountResult {
                 correct: Err(GenericArgCountMismatch { reported: Some(_), .. }),
                 ..
-            } = AstConv::check_generic_arg_count_for_call(
+            } = <dyn AstConv<'_>>::check_generic_arg_count_for_call(
                 tcx,
                 span,
                 def_id,
@@ -1370,7 +1400,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ) -> subst::GenericArg<'tcx> {
                 match (&param.kind, arg) {
                     (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
-                        AstConv::ast_region_to_region(self.fcx, lt, Some(param)).into()
+                        <dyn AstConv<'_>>::ast_region_to_region(self.fcx, lt, Some(param)).into()
                     }
                     (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
                         self.fcx.to_ty(ty).into()
@@ -1423,7 +1453,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         let substs = self_ctor_substs.unwrap_or_else(|| {
-            AstConv::create_substs_for_generic_args(
+            <dyn AstConv<'_>>::create_substs_for_generic_args(
                 tcx,
                 def_id,
                 &[][..],

compiler/rustc_typeck/src/check/fn_ctxt/checks.rs

@@ -875,7 +875,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         match *qpath {
             QPath::Resolved(ref maybe_qself, ref path) => {
                 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
-                let ty = AstConv::res_to_ty(self, self_ty, path, true);
+                let ty = <dyn AstConv<'_>>::res_to_ty(self, self_ty, path, true);
                 (path.res, ty)
             }
             QPath::TypeRelative(ref qself, ref segment) => {
@@ -886,8 +886,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 } else {
                     Res::Err
                 };
-                let result =
-                    AstConv::associated_path_to_ty(self, hir_id, path_span, ty, res, segment, true);
+                let result = <dyn AstConv<'_>>::associated_path_to_ty(
+                    self, hir_id, path_span, ty, res, segment, true,
+                );
                 let ty = result.map(|(ty, _, _)| ty).unwrap_or_else(|_| self.tcx().ty_error());
                 let result = result.map(|(_, kind, def_id)| (kind, def_id));
 
@@ -1000,7 +1001,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                         // would trigger in `is_send::<T::AssocType>();`
                                         // from `typeck-default-trait-impl-assoc-type.rs`.
                                     } else {
-                                        let ty = AstConv::ast_ty_to_ty(self, hir_ty);
+                                        let ty = <dyn AstConv<'_>>::ast_ty_to_ty(self, hir_ty);
                                         let ty = self.resolve_vars_if_possible(ty);
                                         if ty == predicate.self_ty() {
                                             error.obligation.cause.make_mut().span = hir_ty.span;

compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs

@@ -461,7 +461,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // are not, the expectation must have been caused by something else.
                 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
                 let sp = ty.span;
-                let ty = AstConv::ast_ty_to_ty(self, ty);
+                let ty = <dyn AstConv<'_>>::ast_ty_to_ty(self, ty);
                 debug!("suggest_missing_return_type: return type {:?}", ty);
                 debug!("suggest_missing_return_type: expected type {:?}", ty);
                 if ty.kind() == expected.kind() {
@@ -486,7 +486,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
         let found = self.resolve_vars_with_obligations(found);
         if let hir::FnRetTy::Return(ty) = fn_decl.output {
-            let ty = AstConv::ast_ty_to_ty(self, ty);
+            let ty = <dyn AstConv<'_>>::ast_ty_to_ty(self, ty);
             let ty = self.tcx.erase_late_bound_regions(Binder::bind(ty));
             let ty = self.normalize_associated_types_in(expr.span, ty);
             if self.can_coerce(found, ty) {

compiler/rustc_typeck/src/check/inherited.rs

@@ -117,7 +117,7 @@ impl Inherited<'a, 'tcx> {
                 maybe_typeck_results: infcx.in_progress_typeck_results,
             },
             infcx,
-            fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
+            fulfillment_cx: RefCell::new(<dyn TraitEngine<'_>>::new(tcx)),
             locals: RefCell::new(Default::default()),
             deferred_sized_obligations: RefCell::new(Vec::new()),
             deferred_call_resolutions: RefCell::new(Default::default()),