Auto merge of #63463 - matthewjasper:ty_param_cleanup, r=petrochenkov

Don't special case the `Self` parameter by name

This results in a couple of small diagnostic regressions. They could be avoided by keeping the special case just for diagnostics, but that seems worse.

closes #50125
cc #60869

src/librustc/hir/lowering.rs

@@ -2524,15 +2524,6 @@ impl<'a> LoweringContext<'a> {
                 (param_name, kind)
             }
             GenericParamKind::Type { ref default, .. } => {
-                // Don't expose `Self` (recovered "keyword used as ident" parse error).
-                // `rustc::ty` expects `Self` to be only used for a trait's `Self`.
-                // Instead, use `gensym("Self")` to create a distinct name that looks the same.
-                let ident = if param.ident.name == kw::SelfUpper {
-                    param.ident.gensym()
-                } else {
-                    param.ident
-                };
-
                 let add_bounds = add_bounds.get(&param.id).map_or(&[][..], |x| &x);
                 if !add_bounds.is_empty() {
                     let params = self.lower_param_bounds(add_bounds, itctx.reborrow()).into_iter();
@@ -2551,7 +2542,7 @@ impl<'a> LoweringContext<'a> {
                                           .next(),
                 };
 
-                (hir::ParamName::Plain(ident), kind)
+                (hir::ParamName::Plain(param.ident), kind)
             }
             GenericParamKind::Const { ref ty } => {
                 (hir::ParamName::Plain(param.ident), hir::GenericParamKind::Const {

src/librustc/infer/error_reporting/mod.rs

@@ -1329,15 +1329,15 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                     let generics = self.tcx.generics_of(did);
                     // Account for the case where `did` corresponds to `Self`, which doesn't have
                     // the expected type argument.
-                    if !param.is_self() {
+                    if !(generics.has_self && param.index == 0) {
                         let type_param = generics.type_param(param, self.tcx);
                         let hir = &self.tcx.hir();
                         hir.as_local_hir_id(type_param.def_id).map(|id| {
                             // Get the `hir::Param` to verify whether it already has any bounds.
                             // We do this to avoid suggesting code that ends up as `T: 'a'b`,
                             // instead we suggest `T: 'a + 'b` in that case.
                             let mut has_bounds = false;
-                            if let Node::GenericParam(ref param) = hir.get(id) {
+                            if let Node::GenericParam(param) = hir.get(id) {
                                 has_bounds = !param.bounds.is_empty();
                             }
                             let sp = hir.span(id);

src/librustc/traits/object_safety.rs

@@ -91,6 +91,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn astconv_object_safety_violations(self, trait_def_id: DefId)
                                             -> Vec<ObjectSafetyViolation>
     {
+        debug_assert!(self.generics_of(trait_def_id).has_self);
         let violations = traits::supertrait_def_ids(self, trait_def_id)
             .filter(|&def_id| self.predicates_reference_self(def_id, true))
             .map(|_| ObjectSafetyViolation::SupertraitSelf)
@@ -106,16 +107,33 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn object_safety_violations(self, trait_def_id: DefId)
                                     -> Vec<ObjectSafetyViolation>
     {
+        debug_assert!(self.generics_of(trait_def_id).has_self);
         debug!("object_safety_violations: {:?}", trait_def_id);
 
         traits::supertrait_def_ids(self, trait_def_id)
             .flat_map(|def_id| self.object_safety_violations_for_trait(def_id))
             .collect()
     }
 
-    fn object_safety_violations_for_trait(self, trait_def_id: DefId)
-                                          -> Vec<ObjectSafetyViolation>
-    {
+    /// We say a method is *vtable safe* if it can be invoked on a trait
+    /// object.  Note that object-safe traits can have some
+    /// non-vtable-safe methods, so long as they require `Self:Sized` or
+    /// otherwise ensure that they cannot be used when `Self=Trait`.
+    pub fn is_vtable_safe_method(self, trait_def_id: DefId, method: &ty::AssocItem) -> bool {
+        debug_assert!(self.generics_of(trait_def_id).has_self);
+        debug!("is_vtable_safe_method({:?}, {:?})", trait_def_id, method);
+        // Any method that has a `Self : Sized` requisite can't be called.
+        if self.generics_require_sized_self(method.def_id) {
+            return false;
+        }
+
+        match self.virtual_call_violation_for_method(trait_def_id, method) {
+            None | Some(MethodViolationCode::WhereClauseReferencesSelf(_)) => true,
+            Some(_) => false,
+        }
+    }
+
+    fn object_safety_violations_for_trait(self, trait_def_id: DefId) -> Vec<ObjectSafetyViolation> {
         // Check methods for violations.
         let mut violations: Vec<_> = self.associated_items(trait_def_id)
             .filter(|item| item.kind == ty::AssocKind::Method)
@@ -163,14 +181,16 @@ impl<'tcx> TyCtxt<'tcx> {
     fn predicates_reference_self(
         self,
         trait_def_id: DefId,
-        supertraits_only: bool) -> bool
-    {
+        supertraits_only: bool,
+    ) -> bool {
         let trait_ref = ty::Binder::dummy(ty::TraitRef::identity(self, trait_def_id));
         let predicates = if supertraits_only {
             self.super_predicates_of(trait_def_id)
         } else {
             self.predicates_of(trait_def_id)
         };
+        let self_ty = self.types.self_param;
+        let has_self_ty = |t: Ty<'tcx>| t.walk().any(|t| t == self_ty);
         predicates
             .predicates
             .iter()
@@ -179,7 +199,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 match predicate {
                     ty::Predicate::Trait(ref data) => {
                         // In the case of a trait predicate, we can skip the "self" type.
-                        data.skip_binder().input_types().skip(1).any(|t| t.has_self_ty())
+                        data.skip_binder().input_types().skip(1).any(has_self_ty)
                     }
                     ty::Predicate::Projection(ref data) => {
                         // And similarly for projections. This should be redundant with
@@ -199,7 +219,7 @@ impl<'tcx> TyCtxt<'tcx> {
                             .trait_ref(self)
                             .input_types()
                             .skip(1)
-                            .any(|t| t.has_self_ty())
+                            .any(has_self_ty)
                     }
                     ty::Predicate::WellFormed(..) |
                     ty::Predicate::ObjectSafe(..) |
@@ -229,11 +249,11 @@ impl<'tcx> TyCtxt<'tcx> {
         let predicates = predicates.instantiate_identity(self).predicates;
         elaborate_predicates(self, predicates)
             .any(|predicate| match predicate {
-                ty::Predicate::Trait(ref trait_pred) if trait_pred.def_id() == sized_def_id => {
-                    trait_pred.skip_binder().self_ty().is_self()
+                ty::Predicate::Trait(ref trait_pred) => {
+                    trait_pred.def_id() == sized_def_id
+                        && trait_pred.skip_binder().self_ty().is_param(0)
                 }
                 ty::Predicate::Projection(..) |
-                ty::Predicate::Trait(..) |
                 ty::Predicate::Subtype(..) |
                 ty::Predicate::RegionOutlives(..) |
                 ty::Predicate::WellFormed(..) |
@@ -248,11 +268,11 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     /// Returns `Some(_)` if this method makes the containing trait not object safe.
-    fn object_safety_violation_for_method(self,
-                                          trait_def_id: DefId,
-                                          method: &ty::AssocItem)
-                                          -> Option<MethodViolationCode>
-    {
+    fn object_safety_violation_for_method(
+        self,
+        trait_def_id: DefId,
+        method: &ty::AssocItem,
+    ) -> Option<MethodViolationCode> {
         debug!("object_safety_violation_for_method({:?}, {:?})", trait_def_id, method);
         // Any method that has a `Self : Sized` requisite is otherwise
         // exempt from the regulations.
@@ -263,36 +283,15 @@ impl<'tcx> TyCtxt<'tcx> {
         self.virtual_call_violation_for_method(trait_def_id, method)
     }
 
-    /// We say a method is *vtable safe* if it can be invoked on a trait
-    /// object.  Note that object-safe traits can have some
-    /// non-vtable-safe methods, so long as they require `Self:Sized` or
-    /// otherwise ensure that they cannot be used when `Self=Trait`.
-    pub fn is_vtable_safe_method(self,
-                                 trait_def_id: DefId,
-                                 method: &ty::AssocItem)
-                                 -> bool
-    {
-        debug!("is_vtable_safe_method({:?}, {:?})", trait_def_id, method);
-        // Any method that has a `Self : Sized` requisite can't be called.
-        if self.generics_require_sized_self(method.def_id) {
-            return false;
-        }
-
-        match self.virtual_call_violation_for_method(trait_def_id, method) {
-            None | Some(MethodViolationCode::WhereClauseReferencesSelf(_)) => true,
-            Some(_) => false,
-        }
-    }
-
     /// Returns `Some(_)` if this method cannot be called on a trait
     /// object; this does not necessarily imply that the enclosing trait
     /// is not object safe, because the method might have a where clause
     /// `Self:Sized`.
-    fn virtual_call_violation_for_method(self,
-                                         trait_def_id: DefId,
-                                         method: &ty::AssocItem)
-                                         -> Option<MethodViolationCode>
-    {
+    fn virtual_call_violation_for_method(
+        self,
+        trait_def_id: DefId,
+        method: &ty::AssocItem,
+    ) -> Option<MethodViolationCode> {
         // The method's first parameter must be named `self`
         if !method.method_has_self_argument {
             return Some(MethodViolationCode::StaticMethod);
@@ -323,7 +322,9 @@ impl<'tcx> TyCtxt<'tcx> {
                 .collect::<Vec<_>>()
                 // Do a shallow visit so that `contains_illegal_self_type_reference`
                 // may apply it's custom visiting.
-                .visit_tys_shallow(|t| self.contains_illegal_self_type_reference(trait_def_id, t)) {
+                .visit_tys_shallow(|t| {
+                    self.contains_illegal_self_type_reference(trait_def_id, t)
+                }) {
             let span = self.def_span(method.def_id);
             return Some(MethodViolationCode::WhereClauseReferencesSelf(span));
         }
@@ -337,7 +338,7 @@ impl<'tcx> TyCtxt<'tcx> {
         // However, this is already considered object-safe. We allow it as a special case here.
         // FIXME(mikeyhew) get rid of this `if` statement once `receiver_is_dispatchable` allows
         // `Receiver: Unsize<Receiver[Self => dyn Trait]>`
-        if receiver_ty != self.mk_self_type() {
+        if receiver_ty != self.types.self_param {
             if !self.receiver_is_dispatchable(method, receiver_ty) {
                 return Some(MethodViolationCode::UndispatchableReceiver);
             } else {
@@ -404,7 +405,10 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Performs a type substitution to produce the version of receiver_ty when `Self = self_ty`
     /// e.g., for receiver_ty = `Rc<Self>` and self_ty = `Foo`, returns `Rc<Foo>`.
     fn receiver_for_self_ty(
-        self, receiver_ty: Ty<'tcx>, self_ty: Ty<'tcx>, method_def_id: DefId
+        self,
+        receiver_ty: Ty<'tcx>,
+        self_ty: Ty<'tcx>,
+        method_def_id: DefId,
     ) -> Ty<'tcx> {
         debug!("receiver_for_self_ty({:?}, {:?}, {:?})", receiver_ty, self_ty, method_def_id);
         let substs = InternalSubsts::for_item(self, method_def_id, |param, _| {
@@ -555,7 +559,7 @@ impl<'tcx> TyCtxt<'tcx> {
             // Self: Unsize<U>
             let unsize_predicate = ty::TraitRef {
                 def_id: unsize_did,
-                substs: self.mk_substs_trait(self.mk_self_type(), &[unsized_self_ty.into()]),
+                substs: self.mk_substs_trait(self.types.self_param, &[unsized_self_ty.into()]),
             }.to_predicate();
 
             // U: Trait<Arg1, ..., ArgN>
@@ -608,11 +612,11 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    fn contains_illegal_self_type_reference(self,
-                                            trait_def_id: DefId,
-                                            ty: Ty<'tcx>)
-                                            -> bool
-    {
+    fn contains_illegal_self_type_reference(
+        self,
+        trait_def_id: DefId,
+        ty: Ty<'tcx>,
+     ) -> bool {
         // This is somewhat subtle. In general, we want to forbid
         // references to `Self` in the argument and return types,
         // since the value of `Self` is erased. However, there is one
@@ -654,10 +658,11 @@ impl<'tcx> TyCtxt<'tcx> {
 
         let mut supertraits: Option<Vec<ty::PolyTraitRef<'tcx>>> = None;
         let mut error = false;
+        let self_ty = self.types.self_param;
         ty.maybe_walk(|ty| {
             match ty.sty {
-                ty::Param(ref param_ty) => {
-                    if param_ty.is_self() {
+                ty::Param(_) => {
+                    if ty == self_ty {
                         error = true;
                     }
 

src/librustc/ty/context.rs

@@ -173,6 +173,7 @@ pub struct CommonTypes<'tcx> {
     pub f32: Ty<'tcx>,
     pub f64: Ty<'tcx>,
     pub never: Ty<'tcx>,
+    pub self_param: Ty<'tcx>,
     pub err: Ty<'tcx>,
 
     /// Dummy type used for the `Self` of a `TraitRef` created for converting
@@ -915,6 +916,10 @@ impl<'tcx> CommonTypes<'tcx> {
             u128: mk(Uint(ast::UintTy::U128)),
             f32: mk(Float(ast::FloatTy::F32)),
             f64: mk(Float(ast::FloatTy::F64)),
+            self_param: mk(ty::Param(ty::ParamTy {
+                index: 0,
+                name: kw::SelfUpper.as_interned_str(),
+            })),
 
             trait_object_dummy_self: mk(Infer(ty::FreshTy(0))),
         }
@@ -2566,10 +2571,6 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    #[inline]
-    pub fn mk_self_type(self) -> Ty<'tcx> {
-        self.mk_ty_param(0, kw::SelfUpper.as_interned_str())
-    }
 
     pub fn mk_param_from_def(self, param: &ty::GenericParamDef) -> Kind<'tcx> {
         match param.kind {

src/librustc/ty/error.rs

@@ -239,13 +239,7 @@ impl<'tcx> ty::TyS<'tcx> {
             ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
             ty::Projection(_) => "associated type".into(),
             ty::UnnormalizedProjection(_) => "non-normalized associated type".into(),
-            ty::Param(ref p) => {
-                if p.is_self() {
-                    "Self".into()
-                } else {
-                    "type parameter".into()
-                }
-            }
+            ty::Param(_) => "type parameter".into(),
             ty::Opaque(..) => "opaque type".into(),
             ty::Error => "type error".into(),
         }

src/librustc/ty/flags.rs

@@ -1,5 +1,5 @@
 use crate::ty::subst::{SubstsRef, UnpackedKind};
-use crate::ty::{self, Ty, TypeFlags, TypeFoldable, InferConst};
+use crate::ty::{self, Ty, TypeFlags, InferConst};
 use crate::mir::interpret::ConstValue;
 
 #[derive(Debug)]
@@ -86,13 +86,9 @@ impl FlagComputation {
                 self.add_flags(TypeFlags::HAS_TY_ERR)
             }
 
-            &ty::Param(ref p) => {
+            &ty::Param(_) => {
                 self.add_flags(TypeFlags::HAS_FREE_LOCAL_NAMES);
-                if p.is_self() {
-                    self.add_flags(TypeFlags::HAS_SELF);
-                } else {
-                    self.add_flags(TypeFlags::HAS_PARAMS);
-                }
+                self.add_flags(TypeFlags::HAS_PARAMS);
             }
 
             &ty::Generator(_, ref substs, _) => {
@@ -143,11 +139,6 @@ impl FlagComputation {
             }
 
             &ty::Projection(ref data) => {
-                // currently we can't normalize projections that
-                // include bound regions, so track those separately.
-                if !data.has_escaping_bound_vars() {
-                    self.add_flags(TypeFlags::HAS_NORMALIZABLE_PROJECTION);
-                }
                 self.add_flags(TypeFlags::HAS_PROJECTION);
                 self.add_projection_ty(data);
             }
@@ -243,7 +234,7 @@ impl FlagComputation {
         match c.val {
             ConstValue::Unevaluated(_, substs) => {
                 self.add_substs(substs);
-                self.add_flags(TypeFlags::HAS_NORMALIZABLE_PROJECTION | TypeFlags::HAS_PROJECTION);
+                self.add_flags(TypeFlags::HAS_PROJECTION);
             },
             ConstValue::Infer(infer) => {
                 self.add_flags(TypeFlags::HAS_FREE_LOCAL_NAMES | TypeFlags::HAS_CT_INFER);

src/librustc/ty/fold.rs

@@ -85,9 +85,6 @@ pub trait TypeFoldable<'tcx>: fmt::Debug + Clone {
     fn has_param_types(&self) -> bool {
         self.has_type_flags(TypeFlags::HAS_PARAMS)
     }
-    fn has_self_ty(&self) -> bool {
-        self.has_type_flags(TypeFlags::HAS_SELF)
-    }
     fn has_infer_types(&self) -> bool {
         self.has_type_flags(TypeFlags::HAS_TY_INFER)
     }

src/librustc/ty/instance.rs

@@ -298,8 +298,9 @@ impl<'tcx> Instance<'tcx> {
     ) -> Option<Instance<'tcx>> {
         debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
         let fn_sig = tcx.fn_sig(def_id);
-        let is_vtable_shim =
-            fn_sig.inputs().skip_binder().len() > 0 && fn_sig.input(0).skip_binder().is_self();
+        let is_vtable_shim = fn_sig.inputs().skip_binder().len() > 0
+            && fn_sig.input(0).skip_binder().is_param(0)
+            && tcx.generics_of(def_id).has_self;
         if is_vtable_shim {
             debug!(" => associated item with unsizeable self: Self");
             Some(Instance {

src/librustc/ty/layout.rs

@@ -1601,7 +1601,6 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         // resulting from the final codegen session.
         if
             layout.ty.has_param_types() ||
-            layout.ty.has_self_ty() ||
             !self.param_env.caller_bounds.is_empty()
         {
             return;
@@ -1767,7 +1766,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
                 let tail = tcx.struct_tail_erasing_lifetimes(pointee, param_env);
                 match tail.sty {
                     ty::Param(_) | ty::Projection(_) => {
-                        debug_assert!(tail.has_param_types() || tail.has_self_ty());
+                        debug_assert!(tail.has_param_types());
                         Ok(SizeSkeleton::Pointer {
                             non_zero,
                             tail: tcx.erase_regions(&tail)