Auto merge of rust-lang#115361 - compiler-errors:param, r=cjgillot

Don't manually compute param indices when adding implicit `Sized` and `ConstParamHasTy`

We can just use resolve_bound_vars to compute these indices faithfully.

This also makes the code easier to support where clauses on `non_lifetime_binders` (like `where for<T: Debug> ...`, etc, which I've got a [WIP implementation of](rust-lang/rust@master...compiler-errors:rust:non-lifetime-binder-where-clauses)).

r? `@cjgillot`

Author: bors

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -2205,27 +2205,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         err.span_note(span, format!("type parameter `{name}` defined here"));
                     }
                 });
-
-                match tcx.named_bound_var(hir_id) {
-                    Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => {
-                        let name =
-                            tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id.expect_local()));
-                        let br = ty::BoundTy {
-                            var: ty::BoundVar::from_u32(index),
-                            kind: ty::BoundTyKind::Param(def_id, name),
-                        };
-                        Ty::new_bound(tcx, debruijn, br)
-                    }
-                    Some(rbv::ResolvedArg::EarlyBound(_)) => {
-                        let def_id = def_id.expect_local();
-                        let item_def_id = tcx.hir().ty_param_owner(def_id);
-                        let generics = tcx.generics_of(item_def_id);
-                        let index = generics.param_def_id_to_index[&def_id.to_def_id()];
-                        Ty::new_param(tcx, index, tcx.hir().ty_param_name(def_id))
-                    }
-                    Some(rbv::ResolvedArg::Error(guar)) => Ty::new_error(tcx, guar),
-                    arg => bug!("unexpected bound var resolution for {hir_id:?}: {arg:?}"),
-                }
+                self.hir_id_to_bound_ty(hir_id)
             }
             Res::SelfTyParam { .. } => {
                 // `Self` in trait or type alias.
@@ -2394,6 +2374,57 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         }
     }
 
+    // Converts a hir id corresponding to a type parameter to
+    // a early-bound `ty::Param` or late-bound `ty::Bound`.
+    pub(crate) fn hir_id_to_bound_ty(&self, hir_id: hir::HirId) -> Ty<'tcx> {
+        let tcx = self.tcx();
+        match tcx.named_bound_var(hir_id) {
+            Some(rbv::ResolvedArg::LateBound(debruijn, index, def_id)) => {
+                let name = tcx.item_name(def_id);
+                let br = ty::BoundTy {
+                    var: ty::BoundVar::from_u32(index),
+                    kind: ty::BoundTyKind::Param(def_id, name),
+                };
+                Ty::new_bound(tcx, debruijn, br)
+            }
+            Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
+                let def_id = def_id.expect_local();
+                let item_def_id = tcx.hir().ty_param_owner(def_id);
+                let generics = tcx.generics_of(item_def_id);
+                let index = generics.param_def_id_to_index[&def_id.to_def_id()];
+                Ty::new_param(tcx, index, tcx.hir().ty_param_name(def_id))
+            }
+            Some(rbv::ResolvedArg::Error(guar)) => Ty::new_error(tcx, guar),
+            arg => bug!("unexpected bound var resolution for {hir_id:?}: {arg:?}"),
+        }
+    }
+
+    // Converts a hir id corresponding to a const parameter to
+    // a early-bound `ConstKind::Param` or late-bound `ConstKind::Bound`.
+    pub(crate) fn hir_id_to_bound_const(
+        &self,
+        hir_id: hir::HirId,
+        param_ty: Ty<'tcx>,
+    ) -> Const<'tcx> {
+        let tcx = self.tcx();
+        match tcx.named_bound_var(hir_id) {
+            Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
+                // Find the name and index of the const parameter by indexing the generics of
+                // the parent item and construct a `ParamConst`.
+                let item_def_id = tcx.parent(def_id);
+                let generics = tcx.generics_of(item_def_id);
+                let index = generics.param_def_id_to_index[&def_id];
+                let name = tcx.item_name(def_id);
+                ty::Const::new_param(tcx, ty::ParamConst::new(index, name), param_ty)
+            }
+            Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => {
+                ty::Const::new_bound(tcx, debruijn, ty::BoundVar::from_u32(index), param_ty)
+            }
+            Some(rbv::ResolvedArg::Error(guar)) => ty::Const::new_error(tcx, guar, param_ty),
+            arg => bug!("unexpected bound var resolution for {:?}: {arg:?}", hir_id),
+        }
+    }
+
     /// Parses the programmer's textual representation of a type into our
     /// internal notion of a type.
     pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {

compiler/rustc_hir_analysis/src/collect/predicates_of.rs

@@ -162,8 +162,6 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
     };
 
     let generics = tcx.generics_of(def_id);
-    let parent_count = generics.parent_count as u32;
-    let has_own_self = generics.has_self && parent_count == 0;
 
     // Below we'll consider the bounds on the type parameters (including `Self`)
     // and the explicit where-clauses, but to get the full set of predicates
@@ -189,17 +187,6 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
         predicates.insert((trait_ref.to_predicate(tcx), tcx.def_span(def_id)));
     }
 
-    // Collect the region predicates that were declared inline as
-    // well. In the case of parameters declared on a fn or method, we
-    // have to be careful to only iterate over early-bound regions.
-    let mut index = parent_count
-        + has_own_self as u32
-        + super::early_bound_lifetimes_from_generics(tcx, ast_generics).count() as u32;
-
-    trace!(?predicates);
-    trace!(?ast_generics);
-    trace!(?generics);
-
     // Collect the predicates that were written inline by the user on each
     // type parameter (e.g., `<T: Foo>`). Also add `ConstArgHasType` predicates
     // for each const parameter.
@@ -208,10 +195,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
             // We already dealt with early bound lifetimes above.
             GenericParamKind::Lifetime { .. } => (),
             GenericParamKind::Type { .. } => {
-                let name = param.name.ident().name;
-                let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
-                index += 1;
-
+                let param_ty = icx.astconv().hir_id_to_bound_ty(param.hir_id);
                 let mut bounds = Bounds::default();
                 // Params are implicitly sized unless a `?Sized` bound is found
                 icx.astconv().add_implicitly_sized(
@@ -225,23 +209,16 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                 predicates.extend(bounds.clauses());
                 trace!(?predicates);
             }
-            GenericParamKind::Const { .. } => {
-                let name = param.name.ident().name;
-                let param_const = ty::ParamConst::new(index, name);
-
+            hir::GenericParamKind::Const { .. } => {
                 let ct_ty = tcx
                     .type_of(param.def_id.to_def_id())
                     .no_bound_vars()
                     .expect("const parameters cannot be generic");
-
-                let ct = ty::Const::new_param(tcx, param_const, ct_ty);
-
+                let ct = icx.astconv().hir_id_to_bound_const(param.hir_id, ct_ty);
                 predicates.insert((
                     ty::ClauseKind::ConstArgHasType(ct, ct_ty).to_predicate(tcx),
                     param.span,
                 ));
-
-                index += 1;
             }
         }
     }
@@ -252,8 +229,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
         match predicate {
             hir::WherePredicate::BoundPredicate(bound_pred) => {
                 let ty = icx.to_ty(bound_pred.bounded_ty);
-                let bound_vars = icx.tcx.late_bound_vars(bound_pred.hir_id);
-
+                let bound_vars = tcx.late_bound_vars(bound_pred.hir_id);
                 // Keep the type around in a dummy predicate, in case of no bounds.
                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
                 // is still checked for WF.
@@ -296,7 +272,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                         _ => bug!(),
                     };
                     let pred = ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(r1, r2))
-                        .to_predicate(icx.tcx);
+                        .to_predicate(tcx);
                     (pred, span)
                 }))
             }

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -849,6 +849,7 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
         let scope = Scope::TraitRefBoundary { s: self.scope };
         self.with(scope, |this| {
+            walk_list!(this, visit_generic_param, generics.params);
             for param in generics.params {
                 match param.kind {
                     GenericParamKind::Lifetime { .. } => {}
@@ -865,90 +866,86 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                     }
                 }
             }
-            for predicate in generics.predicates {
-                match predicate {
-                    &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
-                        hir_id,
-                        bounded_ty,
-                        bounds,
-                        bound_generic_params,
-                        origin,
-                        ..
-                    }) => {
-                        let (bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) =
-                            bound_generic_params
-                                .iter()
-                                .enumerate()
-                                .map(|(late_bound_idx, param)| {
-                                    let pair = ResolvedArg::late(late_bound_idx as u32, param);
-                                    let r = late_arg_as_bound_arg(this.tcx, &pair.1, param);
-                                    (pair, r)
-                                })
-                                .unzip();
-                        this.record_late_bound_vars(hir_id, binders.clone());
-                        // Even if there are no lifetimes defined here, we still wrap it in a binder
-                        // scope. If there happens to be a nested poly trait ref (an error), that
-                        // will be `Concatenating` anyways, so we don't have to worry about the depth
-                        // being wrong.
-                        let scope = Scope::Binder {
-                            hir_id,
-                            bound_vars,
-                            s: this.scope,
-                            scope_type: BinderScopeType::Normal,
-                            where_bound_origin: Some(origin),
-                        };
-                        this.with(scope, |this| {
-                            this.visit_ty(&bounded_ty);
-                            walk_list!(this, visit_param_bound, bounds);
+            walk_list!(this, visit_where_predicate, generics.predicates);
+        })
+    }
+
+    fn visit_where_predicate(&mut self, predicate: &'tcx hir::WherePredicate<'tcx>) {
+        match predicate {
+            &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
+                hir_id,
+                bounded_ty,
+                bounds,
+                bound_generic_params,
+                origin,
+                ..
+            }) => {
+                let (bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) =
+                    bound_generic_params
+                        .iter()
+                        .enumerate()
+                        .map(|(late_bound_idx, param)| {
+                            let pair = ResolvedArg::late(late_bound_idx as u32, param);
+                            let r = late_arg_as_bound_arg(self.tcx, &pair.1, param);
+                            (pair, r)
                         })
-                    }
-                    &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
-                        lifetime,
-                        bounds,
-                        ..
-                    }) => {
-                        this.visit_lifetime(lifetime);
-                        walk_list!(this, visit_param_bound, bounds);
-
-                        if lifetime.res != hir::LifetimeName::Static {
-                            for bound in bounds {
-                                let hir::GenericBound::Outlives(lt) = bound else {
-                                    continue;
-                                };
-                                if lt.res != hir::LifetimeName::Static {
-                                    continue;
-                                }
-                                this.insert_lifetime(lt, ResolvedArg::StaticLifetime);
-                                this.tcx.struct_span_lint_hir(
-                                    lint::builtin::UNUSED_LIFETIMES,
-                                    lifetime.hir_id,
-                                    lifetime.ident.span,
-                                    format!(
-                                        "unnecessary lifetime parameter `{}`",
-                                        lifetime.ident
-                                    ),
-                                    |lint| {
-                                        let help = format!(
-                                            "you can use the `'static` lifetime directly, in place of `{}`",
-                                            lifetime.ident,
-                                        );
-                                        lint.help(help)
-                                    },
-                                );
-                            }
+                        .unzip();
+                self.record_late_bound_vars(hir_id, binders.clone());
+                // Even if there are no lifetimes defined here, we still wrap it in a binder
+                // scope. If there happens to be a nested poly trait ref (an error), that
+                // will be `Concatenating` anyways, so we don't have to worry about the depth
+                // being wrong.
+                let scope = Scope::Binder {
+                    hir_id,
+                    bound_vars,
+                    s: self.scope,
+                    scope_type: BinderScopeType::Normal,
+                    where_bound_origin: Some(origin),
+                };
+                self.with(scope, |this| {
+                    walk_list!(this, visit_generic_param, bound_generic_params);
+                    this.visit_ty(&bounded_ty);
+                    walk_list!(this, visit_param_bound, bounds);
+                })
+            }
+            &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
+                lifetime,
+                bounds,
+                ..
+            }) => {
+                self.visit_lifetime(lifetime);
+                walk_list!(self, visit_param_bound, bounds);
+
+                if lifetime.res != hir::LifetimeName::Static {
+                    for bound in bounds {
+                        let hir::GenericBound::Outlives(lt) = bound else {
+                            continue;
+                        };
+                        if lt.res != hir::LifetimeName::Static {
+                            continue;
                         }
-                    }
-                    &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
-                        lhs_ty,
-                        rhs_ty,
-                        ..
-                    }) => {
-                        this.visit_ty(lhs_ty);
-                        this.visit_ty(rhs_ty);
+                        self.insert_lifetime(lt, ResolvedArg::StaticLifetime);
+                        self.tcx.struct_span_lint_hir(
+                            lint::builtin::UNUSED_LIFETIMES,
+                            lifetime.hir_id,
+                            lifetime.ident.span,
+                            format!("unnecessary lifetime parameter `{}`", lifetime.ident),
+                            |lint| {
+                                let help = format!(
+                                    "you can use the `'static` lifetime directly, in place of `{}`",
+                                    lifetime.ident,
+                                );
+                                lint.help(help)
+                            },
+                        );
                     }
                 }
             }
-        })
+            &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate { lhs_ty, rhs_ty, .. }) => {
+                self.visit_ty(lhs_ty);
+                self.visit_ty(rhs_ty);
+            }
+        }
     }
 
     fn visit_param_bound(&mut self, bound: &'tcx hir::GenericBound<'tcx>) {
@@ -986,6 +983,18 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
             intravisit::walk_anon_const(this, c);
         });
     }
+
+    fn visit_generic_param(&mut self, p: &'tcx GenericParam<'tcx>) {
+        match p.kind {
+            GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
+                self.resolve_type_ref(p.def_id, p.hir_id);
+            }
+            GenericParamKind::Lifetime { .. } => {
+                // No need to resolve lifetime params, we don't use them for things
+                // like implicit `?Sized` or const-param-has-ty predicates.
+            }
+        }
+    }
 }
 
 fn object_lifetime_default(tcx: TyCtxt<'_>, param_def_id: LocalDefId) -> ObjectLifetimeDefault {