Rollup merge of #114314 - compiler-errors:sized-crit, r=lcnr

Tweaks to `adt_sized_constraint`

fixes a comment, but also some other nits.

r? lcnr

Author: matthiaskrgr

Diff for: compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -1462,7 +1462,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     let traits: Vec<_> =
                         self.probe_traits_that_match_assoc_ty(qself_ty, assoc_ident);
 
-                    // Don't print `TyErr` to the user.
+                    // Don't print `ty::Error` to the user.
                     self.report_ambiguous_associated_type(
                         span,
                         &[qself_ty.to_string()],

Diff for: compiler/rustc_hir_typeck/src/closure.rs

@@ -795,7 +795,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     /// Converts the types that the user supplied, in case that doing
     /// so should yield an error, but returns back a signature where
-    /// all parameters are of type `TyErr`.
+    /// all parameters are of type `ty::Error`.
     fn error_sig_of_closure(
         &self,
         decl: &hir::FnDecl<'_>,

Diff for: compiler/rustc_middle/src/query/mod.rs

@@ -706,7 +706,7 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query adt_sized_constraint(key: DefId) -> &'tcx [Ty<'tcx>] {
+    query adt_sized_constraint(key: DefId) -> ty::EarlyBinder<&'tcx ty::List<Ty<'tcx>>> {
         desc { |tcx| "computing `Sized` constraints for `{}`", tcx.def_path_str(key) }
     }
 

Diff for: compiler/rustc_middle/src/ty/adt.rs

@@ -562,18 +562,10 @@ impl<'tcx> AdtDef<'tcx> {
         tcx.adt_destructor(self.did())
     }
 
-    /// Returns a list of types such that `Self: Sized` if and only
-    /// if that type is `Sized`, or `TyErr` if this type is recursive.
-    ///
-    /// Oddly enough, checking that the sized-constraint is `Sized` is
-    /// actually more expressive than checking all members:
-    /// the `Sized` trait is inductive, so an associated type that references
-    /// `Self` would prevent its containing ADT from being `Sized`.
-    ///
-    /// Due to normalization being eager, this applies even if
-    /// the associated type is behind a pointer (e.g., issue #31299).
-    pub fn sized_constraint(self, tcx: TyCtxt<'tcx>) -> ty::EarlyBinder<&'tcx [Ty<'tcx>]> {
-        ty::EarlyBinder::bind(tcx.adt_sized_constraint(self.did()))
+    /// Returns a list of types such that `Self: Sized` if and only if that
+    /// type is `Sized`, or `ty::Error` if this type has a recursive layout.
+    pub fn sized_constraint(self, tcx: TyCtxt<'tcx>) -> ty::EarlyBinder<&'tcx ty::List<Ty<'tcx>>> {
+        tcx.adt_sized_constraint(self.did())
     }
 }
 

Diff for: compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs

@@ -150,7 +150,7 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_sized_trait<'tcx>(
 
         ty::Adt(def, args) => {
             let sized_crit = def.sized_constraint(ecx.tcx());
-            Ok(sized_crit.iter_instantiated_copied(ecx.tcx(), args).collect())
+            Ok(sized_crit.iter_instantiated(ecx.tcx(), args).collect())
         }
     }
 }

Diff for: compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -2099,7 +2099,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 Where(
                     obligation
                         .predicate
-                        .rebind(sized_crit.iter_instantiated_copied(self.tcx(), args).collect()),
+                        .rebind(sized_crit.iter_instantiated(self.tcx(), args).collect()),
                 )
             }
 

Diff for: compiler/rustc_ty_utils/src/ty.rs

@@ -42,7 +42,7 @@ fn sized_constraint_for_ty<'tcx>(
             let adt_tys = adt.sized_constraint(tcx);
             debug!("sized_constraint_for_ty({:?}) intermediate = {:?}", ty, adt_tys);
             adt_tys
-                .iter_instantiated_copied(tcx, args)
+                .iter_instantiated(tcx, args)
                 .flat_map(|ty| sized_constraint_for_ty(tcx, adtdef, ty))
                 .collect()
         }
@@ -58,11 +58,18 @@ fn sized_constraint_for_ty<'tcx>(
             // we know that `T` is Sized and do not need to check
             // it on the impl.
 
-            let Some(sized_trait) = tcx.lang_items().sized_trait() else { return vec![ty] };
-            let sized_predicate =
-                ty::TraitRef::new(tcx, sized_trait, [ty]).without_const().to_predicate(tcx);
+            let Some(sized_trait_def_id) = tcx.lang_items().sized_trait() else { return vec![ty] };
             let predicates = tcx.predicates_of(adtdef.did()).predicates;
-            if predicates.iter().any(|(p, _)| *p == sized_predicate) { vec![] } else { vec![ty] }
+            if predicates.iter().any(|(p, _)| {
+                p.as_trait_clause().is_some_and(|trait_pred| {
+                    trait_pred.def_id() == sized_trait_def_id
+                        && trait_pred.self_ty().skip_binder() == ty
+                })
+            }) {
+                vec![]
+            } else {
+                vec![ty]
+            }
         }
 
         Placeholder(..) | Bound(..) | Infer(..) => {
@@ -92,10 +99,13 @@ fn defaultness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Defaultness {
 ///     - a tuple of type parameters or projections, if there are multiple
 ///       such.
 ///     - an Error, if a type is infinitely sized
-fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> &[Ty<'_>] {
+fn adt_sized_constraint<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    def_id: DefId,
+) -> ty::EarlyBinder<&'tcx ty::List<Ty<'tcx>>> {
     if let Some(def_id) = def_id.as_local() {
         if matches!(tcx.representability(def_id), ty::Representability::Infinite) {
-            return tcx.mk_type_list(&[Ty::new_misc_error(tcx)]);
+            return ty::EarlyBinder::bind(tcx.mk_type_list(&[Ty::new_misc_error(tcx)]));
         }
     }
     let def = tcx.adt_def(def_id);
@@ -107,7 +117,7 @@ fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> &[Ty<'_>] {
 
     debug!("adt_sized_constraint: {:?} => {:?}", def, result);
 
-    result
+    ty::EarlyBinder::bind(result)
 }
 
 /// See `ParamEnv` struct definition for details.