Rollup merge of #107486 - compiler-errors:bound-ty-keep-name, r=oli-obk

Track bound types like bound regions

When we instantiate bound types into placeholder types, we throw away the names for some reason. These names are particularly useful for error reporting once we have `for<T>` binders.

r? types

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -1930,7 +1930,7 @@ pub(super) fn check_type_bounds<'tcx>(
         smallvec::SmallVec::with_capacity(defs.count());
     InternalSubsts::fill_single(&mut substs, defs, &mut |param, _| match param.kind {
         GenericParamDefKind::Type { .. } => {
-            let kind = ty::BoundTyKind::Param(param.name);
+            let kind = ty::BoundTyKind::Param(param.def_id, param.name);
             let bound_var = ty::BoundVariableKind::Ty(kind);
             bound_vars.push(bound_var);
             tcx.mk_ty(ty::Bound(

compiler/rustc_infer/src/infer/higher_ranked/mod.rs

@@ -90,7 +90,7 @@ impl<'tcx> InferCtxt<'tcx> {
             types: &mut |bound_ty: ty::BoundTy| {
                 self.tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
                     universe: next_universe,
-                    name: bound_ty.var,
+                    name: bound_ty.kind,
                 }))
             },
             consts: &mut |bound_var: ty::BoundVar, ty| {

compiler/rustc_infer/src/infer/mod.rs

@@ -2044,7 +2044,7 @@ fn replace_param_and_infer_substs_with_placeholder<'tcx>(
 ) -> SubstsRef<'tcx> {
     struct ReplaceParamAndInferWithPlaceholder<'tcx> {
         tcx: TyCtxt<'tcx>,
-        idx: usize,
+        idx: u32,
     }
 
     impl<'tcx> TypeFolder<'tcx> for ReplaceParamAndInferWithPlaceholder<'tcx> {
@@ -2056,7 +2056,7 @@ fn replace_param_and_infer_substs_with_placeholder<'tcx>(
             if let ty::Infer(_) = t.kind() {
                 self.tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
                     universe: ty::UniverseIndex::ROOT,
-                    name: ty::BoundVar::from_usize({
+                    name: ty::BoundTyKind::Anon({
                         let idx = self.idx;
                         self.idx += 1;
                         idx
@@ -2077,7 +2077,7 @@ fn replace_param_and_infer_substs_with_placeholder<'tcx>(
                 self.tcx.mk_const(
                     ty::PlaceholderConst {
                         universe: ty::UniverseIndex::ROOT,
-                        name: ty::BoundVar::from_usize({
+                        name: ty::BoundVar::from_u32({
                             let idx = self.idx;
                             self.idx += 1;
                             idx

compiler/rustc_middle/src/ty/fold.rs

@@ -610,7 +610,9 @@ impl<'tcx> TyCtxt<'tcx> {
                 let index = entry.index();
                 let var = ty::BoundVar::from_usize(index);
                 let kind = entry
-                    .or_insert_with(|| ty::BoundVariableKind::Ty(ty::BoundTyKind::Anon))
+                    .or_insert_with(|| {
+                        ty::BoundVariableKind::Ty(ty::BoundTyKind::Anon(index as u32))
+                    })
                     .expect_ty();
                 self.tcx.mk_ty(ty::Bound(ty::INNERMOST, BoundTy { var, kind }))
             }

compiler/rustc_middle/src/ty/mod.rs

@@ -1369,7 +1369,7 @@ pub struct Placeholder<T> {
 
 pub type PlaceholderRegion = Placeholder<BoundRegionKind>;
 
-pub type PlaceholderType = Placeholder<BoundVar>;
+pub type PlaceholderType = Placeholder<BoundTyKind>;
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -698,8 +698,10 @@ pub trait PrettyPrinter<'tcx>:
             ty::Error(_) => p!("[type error]"),
             ty::Param(ref param_ty) => p!(print(param_ty)),
             ty::Bound(debruijn, bound_ty) => match bound_ty.kind {
-                ty::BoundTyKind::Anon => self.pretty_print_bound_var(debruijn, bound_ty.var)?,
+                ty::BoundTyKind::Anon(bv) => {
-                ty::BoundTyKind::Param(p) => p!(write("{}", p)),
+                    self.pretty_print_bound_var(debruijn, ty::BoundVar::from_u32(bv))?
+                }
+                ty::BoundTyKind::Param(_, s) => p!(write("{}", s)),
             },
             ty::Adt(def, substs) => {
                 p!(print_def_path(def.did(), substs));

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -240,6 +240,7 @@ TrivialTypeTraversalAndLiftImpls! {
     crate::ty::AssocKind,
     crate::ty::AliasKind,
     crate::ty::Placeholder<crate::ty::BoundRegionKind>,
+    crate::ty::Placeholder<crate::ty::BoundTyKind>,
     crate::ty::ClosureKind,
     crate::ty::FreeRegion,
     crate::ty::InferTy,

compiler/rustc_middle/src/ty/sty.rs

@@ -1504,13 +1504,22 @@ pub struct BoundTy {
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
 #[derive(HashStable)]
 pub enum BoundTyKind {
-    Anon,
+    Anon(u32),
-    Param(Symbol),
+    Param(DefId, Symbol),
+}
+
+impl BoundTyKind {
+    pub fn expect_anon(self) -> u32 {
+        match self {
+            BoundTyKind::Anon(i) => i,
+            _ => bug!(),
+        }
+    }
 }
 
 impl From<BoundVar> for BoundTy {
     fn from(var: BoundVar) -> Self {
-        BoundTy { var, kind: BoundTyKind::Anon }
+        BoundTy { var, kind: BoundTyKind::Anon(var.as_u32()) }
     }
 }
 

compiler/rustc_trait_selection/src/traits/project.rs

@@ -783,7 +783,7 @@ impl<'tcx> TypeFolder<'tcx> for BoundVarReplacer<'_, 'tcx> {
             }
             ty::Bound(debruijn, bound_ty) if debruijn >= self.current_index => {
                 let universe = self.universe_for(debruijn);
-                let p = ty::PlaceholderType { universe, name: bound_ty.var };
+                let p = ty::PlaceholderType { universe, name: bound_ty.kind };
                 self.mapped_types.insert(p, bound_ty);
                 self.infcx.tcx.mk_ty(ty::Placeholder(p))
             }

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -524,7 +524,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                             .kind
                         {
                             GenericParamDefKind::Type { .. } => {
-                                let kind = ty::BoundTyKind::Param(param.name);
+                                let kind = ty::BoundTyKind::Param(param.def_id, param.name);
                                 let bound_var = ty::BoundVariableKind::Ty(kind);
                                 bound_vars.push(bound_var);
                                 tcx.mk_ty(ty::Bound(

compiler/rustc_traits/src/chalk/db.rs

@@ -725,7 +725,7 @@ fn bound_vars_for_item(tcx: TyCtxt<'_>, def_id: DefId) -> SubstsRef<'_> {
                 ty::INNERMOST,
                 ty::BoundTy {
                     var: ty::BoundVar::from(param.index),
-                    kind: ty::BoundTyKind::Param(param.name),
+                    kind: ty::BoundTyKind::Param(param.def_id, param.name),
                 },
             ))
             .into(),

compiler/rustc_traits/src/chalk/lowering.rs

@@ -370,7 +370,7 @@ impl<'tcx> LowerInto<'tcx, chalk_ir::Ty<RustInterner<'tcx>>> for Ty<'tcx> {
             ty::Placeholder(_placeholder) => {
                 chalk_ir::TyKind::Placeholder(chalk_ir::PlaceholderIndex {
                     ui: chalk_ir::UniverseIndex { counter: _placeholder.universe.as_usize() },
-                    idx: _placeholder.name.as_usize(),
+                    idx: _placeholder.name.expect_anon() as usize,
                 })
             }
             ty::Infer(_infer) => unimplemented!(),
@@ -452,10 +452,6 @@ impl<'tcx> LowerInto<'tcx, Ty<'tcx>> for &chalk_ir::Ty<RustInterner<'tcx>> {
             ),
             TyKind::Foreign(def_id) => ty::Foreign(def_id.0),
             TyKind::Error => return interner.tcx.ty_error(),
-            TyKind::Placeholder(placeholder) => ty::Placeholder(ty::Placeholder {
-                universe: ty::UniverseIndex::from_usize(placeholder.ui.counter),
-                name: ty::BoundVar::from_usize(placeholder.idx),
-            }),
             TyKind::Alias(alias_ty) => match alias_ty {
                 chalk_ir::AliasTy::Projection(projection) => ty::Alias(
                     ty::Projection,
@@ -473,13 +469,17 @@ impl<'tcx> LowerInto<'tcx, Ty<'tcx>> for &chalk_ir::Ty<RustInterner<'tcx>> {
                 ),
             },
             TyKind::Function(_quantified_ty) => unimplemented!(),
-            TyKind::BoundVar(_bound) => ty::Bound(
+            TyKind::BoundVar(bound) => ty::Bound(
-                ty::DebruijnIndex::from_usize(_bound.debruijn.depth() as usize),
+                ty::DebruijnIndex::from_usize(bound.debruijn.depth() as usize),
                 ty::BoundTy {
-                    var: ty::BoundVar::from_usize(_bound.index),
+                    var: ty::BoundVar::from_usize(bound.index),
-                    kind: ty::BoundTyKind::Anon,
+                    kind: ty::BoundTyKind::Anon(bound.index as u32),
                 },
             ),
+            TyKind::Placeholder(placeholder) => ty::Placeholder(ty::Placeholder {
+                universe: ty::UniverseIndex::from_usize(placeholder.ui.counter),
+                name: ty::BoundTyKind::Anon(placeholder.idx as u32),
+            }),
             TyKind::InferenceVar(_, _) => unimplemented!(),
             TyKind::Dyn(_) => unimplemented!(),
         };
@@ -504,7 +504,7 @@ impl<'tcx> LowerInto<'tcx, chalk_ir::Lifetime<RustInterner<'tcx>>> for Region<'t
             ty::RePlaceholder(placeholder_region) => {
                 chalk_ir::LifetimeData::Placeholder(chalk_ir::PlaceholderIndex {
                     ui: chalk_ir::UniverseIndex { counter: placeholder_region.universe.index() },
-                    idx: 0,
+                    idx: 0, // FIXME: This `idx: 0` is sus.
                 })
                 .intern(interner)
             }
@@ -674,7 +674,7 @@ impl<'tcx> LowerInto<'tcx, chalk_ir::Binders<chalk_ir::QuantifiedWhereClauses<Ru
         let self_ty = interner.tcx.mk_ty(ty::Bound(
             // This is going to be wrapped in a binder
             ty::DebruijnIndex::from_usize(1),
-            ty::BoundTy { var: ty::BoundVar::from_usize(0), kind: ty::BoundTyKind::Anon },
+            ty::BoundTy { var: ty::BoundVar::from_usize(0), kind: ty::BoundTyKind::Anon(0) },
         ));
         let where_clauses = predicates.into_iter().map(|predicate| {
             let (predicate, binders, _named_regions) =
@@ -1038,7 +1038,7 @@ pub(crate) struct ParamsSubstitutor<'tcx> {
     binder_index: ty::DebruijnIndex,
     list: Vec<rustc_middle::ty::ParamTy>,
     next_ty_placeholder: usize,
-    pub(crate) params: rustc_data_structures::fx::FxHashMap<usize, rustc_middle::ty::ParamTy>,
+    pub(crate) params: rustc_data_structures::fx::FxHashMap<u32, rustc_middle::ty::ParamTy>,
     pub(crate) named_regions: BTreeMap<DefId, u32>,
 }
 
@@ -1072,15 +1072,15 @@ impl<'tcx> TypeFolder<'tcx> for ParamsSubstitutor<'tcx> {
             ty::Param(param) => match self.list.iter().position(|r| r == &param) {
                 Some(idx) => self.tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
                     universe: ty::UniverseIndex::from_usize(0),
-                    name: ty::BoundVar::from_usize(idx),
+                    name: ty::BoundTyKind::Anon(idx as u32),
                 })),
                 None => {
                     self.list.push(param);
                     let idx = self.list.len() - 1 + self.next_ty_placeholder;
-                    self.params.insert(idx, param);
+                    self.params.insert(idx as u32, param);
                     self.tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
                         universe: ty::UniverseIndex::from_usize(0),
-                        name: ty::BoundVar::from_usize(idx),
+                        name: ty::BoundTyKind::Anon(idx as u32),
                     }))
                 }
             },
@@ -1119,13 +1119,13 @@ impl<'tcx> TypeFolder<'tcx> for ParamsSubstitutor<'tcx> {
 
 pub(crate) struct ReverseParamsSubstitutor<'tcx> {
     tcx: TyCtxt<'tcx>,
-    params: rustc_data_structures::fx::FxHashMap<usize, rustc_middle::ty::ParamTy>,
+    params: rustc_data_structures::fx::FxHashMap<u32, rustc_middle::ty::ParamTy>,
 }
 
 impl<'tcx> ReverseParamsSubstitutor<'tcx> {
     pub(crate) fn new(
         tcx: TyCtxt<'tcx>,
-        params: rustc_data_structures::fx::FxHashMap<usize, rustc_middle::ty::ParamTy>,
+        params: rustc_data_structures::fx::FxHashMap<u32, rustc_middle::ty::ParamTy>,
     ) -> Self {
         Self { tcx, params }
     }
@@ -1139,7 +1139,7 @@ impl<'tcx> TypeFolder<'tcx> for ReverseParamsSubstitutor<'tcx> {
     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
         match *t.kind() {
             ty::Placeholder(ty::PlaceholderType { universe: ty::UniverseIndex::ROOT, name }) => {
-                match self.params.get(&name.as_usize()) {
+                match self.params.get(&name.expect_anon()) {
                     Some(param) => self.tcx.mk_ty(ty::Param(*param)),
                     None => t,
                 }
@@ -1171,7 +1171,8 @@ impl<'tcx> TypeVisitor<'tcx> for PlaceholdersCollector {
     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         match t.kind() {
             ty::Placeholder(p) if p.universe == self.universe_index => {
-                self.next_ty_placeholder = self.next_ty_placeholder.max(p.name.as_usize() + 1);
+                self.next_ty_placeholder =
+                    self.next_ty_placeholder.max(p.name.expect_anon() as usize + 1);
             }
 
             _ => (),
@@ -1186,6 +1187,7 @@ impl<'tcx> TypeVisitor<'tcx> for PlaceholdersCollector {
                 if let ty::BoundRegionKind::BrAnon(anon, _) = p.name {
                     self.next_anon_region_placeholder = self.next_anon_region_placeholder.max(anon);
                 }
+                // FIXME: This doesn't seem to handle BrNamed at all?
             }
 
             _ => (),

compiler/rustc_traits/src/chalk/mod.rs

@@ -6,12 +6,10 @@
 pub(crate) mod db;
 pub(crate) mod lowering;
 
-use rustc_data_structures::fx::FxHashMap;
-
 use rustc_middle::infer::canonical::{CanonicalTyVarKind, CanonicalVarKind};
 use rustc_middle::traits::ChalkRustInterner;
 use rustc_middle::ty::query::Providers;
-use rustc_middle::ty::{self, ParamTy, TyCtxt, TypeFoldable, TypeVisitable};
+use rustc_middle::ty::{self, TyCtxt, TypeFoldable, TypeVisitable};
 
 use rustc_infer::infer::canonical::{
     Canonical, CanonicalVarValues, Certainty, QueryRegionConstraints, QueryResponse,
@@ -41,7 +39,7 @@ pub(crate) fn evaluate_goal<'tcx>(
     let mut params_substitutor =
         ParamsSubstitutor::new(tcx, placeholders_collector.next_ty_placeholder);
     let obligation = obligation.fold_with(&mut params_substitutor);
-    let params: FxHashMap<usize, ParamTy> = params_substitutor.params;
+    let params = params_substitutor.params;
 
     let max_universe = obligation.max_universe.index();