Uplift and start using check_args_compatible more liberally

compiler/rustc_middle/src/ty/context.rs

@@ -1954,33 +1954,90 @@ impl<'tcx> TyCtxt<'tcx> {
         if pred.kind() != binder { self.mk_predicate(binder) } else { pred }
     }
 
+    pub fn check_args_compatible(self, def_id: DefId, args: &'tcx [ty::GenericArg<'tcx>]) -> bool {
+        self.check_args_compatible_inner(def_id, args, false)
+    }
+
+    fn check_args_compatible_inner(
+        self,
+        def_id: DefId,
+        args: &'tcx [ty::GenericArg<'tcx>],
+        nested: bool,
+    ) -> bool {
+        let generics = self.generics_of(def_id);
+
+        // IATs themselves have a weird arg setup (self + own args), but nested items *in* IATs
+        // (namely: opaques, i.e. ATPITs) do not.
+        let own_args = if !nested
+            && let DefKind::AssocTy = self.def_kind(def_id)
+            && let DefKind::Impl { of_trait: false } = self.def_kind(self.parent(def_id))
+        {
+            if generics.params.len() + 1 != args.len() {
+                return false;
+            }
+
+            if !matches!(args[0].unpack(), ty::GenericArgKind::Type(_)) {
+                return false;
+            }
+
+            &args[1..]
+        } else {
+            if generics.count() != args.len() {
+                return false;
+            }
+
+            let (parent_args, own_args) = args.split_at(generics.parent_count);
+
+            if let Some(parent) = generics.parent
+                && !self.check_args_compatible_inner(parent, parent_args, true)
+            {
+                return false;
+            }
+
+            own_args
+        };
+
+        for (param, arg) in std::iter::zip(&generics.params, own_args) {
+            match (&param.kind, arg.unpack()) {
+                (ty::GenericParamDefKind::Type { .. }, ty::GenericArgKind::Type(_))
+                | (ty::GenericParamDefKind::Lifetime, ty::GenericArgKind::Lifetime(_))
+                | (ty::GenericParamDefKind::Const { .. }, ty::GenericArgKind::Const(_)) => {}
+                _ => return false,
+            }
+        }
+
+        true
+    }
+
+    pub fn assert_args_compatible(self, def_id: DefId, args: &'tcx [ty::GenericArg<'tcx>]) {
+        if !self.check_args_compatible(def_id, args) {
+            if let DefKind::AssocTy = self.def_kind(def_id)
+                && let DefKind::Impl { of_trait: false } = self.def_kind(self.parent(def_id))
+            {
+                bug!()
+            } else {
+                bug!(
+                    "args not compatible with generics for {}: args={:#?}, generics={:#?}",
+                    self.def_path_str(def_id),
+                    args,
+                    ty::GenericArgs::identity_for_item(self, def_id)
+                );
+            }
+        }
+    }
+
     #[inline(always)]
     pub(crate) fn check_and_mk_args(
         self,
         _def_id: DefId,
         args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> GenericArgsRef<'tcx> {
-        let args = args.into_iter().map(Into::into);
+        let args = self.mk_args_from_iter(args.into_iter().map(Into::into));
         #[cfg(debug_assertions)]
         {
-            let generics = self.generics_of(_def_id);
-
-            let n = if let DefKind::AssocTy = self.def_kind(_def_id)
-                && let DefKind::Impl { of_trait: false } = self.def_kind(self.parent(_def_id))
-            {
-                // If this is an inherent projection.
-                generics.params.len() + 1
-            } else {
-                generics.count()
-            };
-            assert_eq!(
-                (n, Some(n)),
-                args.size_hint(),
-                "wrong number of generic parameters for {_def_id:?}: {:?}",
-                args.collect::<Vec<_>>(),
-            );
+            self.assert_args_compatible(_def_id, args);
         }
-        self.mk_args_from_iter(args)
+        args
     }
 
     #[inline]

compiler/rustc_middle/src/ty/sty.rs

@@ -1624,13 +1624,9 @@ impl<'tcx> Ty<'tcx> {
 
     #[inline]
     pub fn new_adt(tcx: TyCtxt<'tcx>, def: AdtDef<'tcx>, args: GenericArgsRef<'tcx>) -> Ty<'tcx> {
-        debug_assert_eq!(
-            tcx.generics_of(def.did()).count(),
-            args.len(),
-            "wrong number of args for ADT: {:#?} vs {:#?}",
-            tcx.generics_of(def.did()).params,
-            args
-        );
+        if cfg!(debug_assertions) {
+            tcx.assert_args_compatible(def.did(), args);
+        }
         Ty::new(tcx, Adt(def, args))
     }
 
@@ -1711,11 +1707,9 @@ impl<'tcx> Ty<'tcx> {
         def_id: DefId,
         closure_args: GenericArgsRef<'tcx>,
     ) -> Ty<'tcx> {
-        debug_assert_eq!(
-            closure_args.len(),
-            tcx.generics_of(tcx.typeck_root_def_id(def_id)).count() + 3,
-            "closure constructed with incorrect generic parameters"
-        );
+        if cfg!(debug_assertions) {
+            tcx.assert_args_compatible(def_id, closure_args);
+        }
         Ty::new(tcx, Closure(def_id, closure_args))
     }
 
@@ -1725,11 +1719,9 @@ impl<'tcx> Ty<'tcx> {
         def_id: DefId,
         closure_args: GenericArgsRef<'tcx>,
     ) -> Ty<'tcx> {
-        debug_assert_eq!(
-            closure_args.len(),
-            tcx.generics_of(tcx.typeck_root_def_id(def_id)).count() + 5,
-            "closure constructed with incorrect generic parameters"
-        );
+        if cfg!(debug_assertions) {
+            tcx.assert_args_compatible(def_id, closure_args);
+        }
         Ty::new(tcx, CoroutineClosure(def_id, closure_args))
     }
 
@@ -1739,11 +1731,9 @@ impl<'tcx> Ty<'tcx> {
         def_id: DefId,
         coroutine_args: GenericArgsRef<'tcx>,
     ) -> Ty<'tcx> {
-        debug_assert_eq!(
-            coroutine_args.len(),
-            tcx.generics_of(tcx.typeck_root_def_id(def_id)).count() + 6,
-            "coroutine constructed with incorrect number of generic parameters"
-        );
+        if cfg!(debug_assertions) {
+            tcx.assert_args_compatible(def_id, coroutine_args);
+        }
         Ty::new(tcx, Coroutine(def_id, coroutine_args))
     }
 

compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs

@@ -1,4 +1,4 @@
-use crate::traits::{check_args_compatible, specialization_graph};
+use crate::traits::specialization_graph;
 
 use super::assembly::structural_traits::AsyncCallableRelevantTypes;
 use super::assembly::{self, structural_traits, Candidate};
@@ -247,7 +247,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
                 assoc_def.defining_node,
             );
 
-            if !check_args_compatible(tcx, assoc_def.item, args) {
+            if !tcx.check_args_compatible(assoc_def.item.def_id, args) {
                 return error_response(
                     ecx,
                     "associated item has mismatched generic item arguments",

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -61,12 +61,12 @@ pub use self::specialize::{
 pub use self::structural_match::search_for_structural_match_violation;
 pub use self::structural_normalize::StructurallyNormalizeExt;
 pub use self::util::elaborate;
-pub use self::util::{
-    check_args_compatible, supertrait_def_ids, supertraits, transitive_bounds,
-    transitive_bounds_that_define_assoc_item, SupertraitDefIds,
-};
 pub use self::util::{expand_trait_aliases, TraitAliasExpander};
 pub use self::util::{get_vtable_index_of_object_method, impl_item_is_final, upcast_choices};
+pub use self::util::{
+    supertrait_def_ids, supertraits, transitive_bounds, transitive_bounds_that_define_assoc_item,
+    SupertraitDefIds,
+};
 pub use self::util::{with_replaced_escaping_bound_vars, BoundVarReplacer, PlaceholderReplacer};
 
 pub use rustc_infer::traits::*;

compiler/rustc_trait_selection/src/traits/project.rs

@@ -2,7 +2,6 @@
 
 use std::ops::ControlFlow;
 
-use super::check_args_compatible;
 use super::specialization_graph;
 use super::translate_args;
 use super::util;
@@ -2030,7 +2029,7 @@ fn confirm_impl_candidate<'cx, 'tcx>(
     } else {
         ty.map_bound(|ty| ty.into())
     };
-    if !check_args_compatible(tcx, assoc_ty.item, args) {
+    if !tcx.check_args_compatible(assoc_ty.item.def_id, args) {
         let err = Ty::new_error_with_message(
             tcx,
             obligation.cause.span,

compiler/rustc_trait_selection/src/traits/util.rs

@@ -344,46 +344,6 @@ pub enum TupleArgumentsFlag {
     No,
 }
 
-// Verify that the trait item and its implementation have compatible args lists
-pub fn check_args_compatible<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    assoc_item: ty::AssocItem,
-    args: ty::GenericArgsRef<'tcx>,
-) -> bool {
-    fn check_args_compatible_inner<'tcx>(
-        tcx: TyCtxt<'tcx>,
-        generics: &'tcx ty::Generics,
-        args: &'tcx [ty::GenericArg<'tcx>],
-    ) -> bool {
-        if generics.count() != args.len() {
-            return false;
-        }
-
-        let (parent_args, own_args) = args.split_at(generics.parent_count);
-
-        if let Some(parent) = generics.parent
-            && let parent_generics = tcx.generics_of(parent)
-            && !check_args_compatible_inner(tcx, parent_generics, parent_args)
-        {
-            return false;
-        }
-
-        for (param, arg) in std::iter::zip(&generics.params, own_args) {
-            match (&param.kind, arg.unpack()) {
-                (ty::GenericParamDefKind::Type { .. }, ty::GenericArgKind::Type(_))
-                | (ty::GenericParamDefKind::Lifetime, ty::GenericArgKind::Lifetime(_))
-                | (ty::GenericParamDefKind::Const { .. }, ty::GenericArgKind::Const(_)) => {}
-                _ => return false,
-            }
-        }
-
-        true
-    }
-
-    let generics = tcx.generics_of(assoc_item.def_id);
-    check_args_compatible_inner(tcx, generics, args)
-}
-
 /// Executes `f` on `value` after replacing all escaping bound variables with placeholders
 /// and then replaces these placeholders with the original bound variables in the result.
 ///

compiler/rustc_ty_utils/src/opaque_types.rs

@@ -7,7 +7,6 @@ use rustc_middle::ty::util::{CheckRegions, NotUniqueParam};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::ty::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
 use rustc_span::Span;
-use rustc_trait_selection::traits::check_args_compatible;
 
 use crate::errors::{DuplicateArg, NotParam};
 
@@ -250,7 +249,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector<'tcx> {
                                 ty::GenericArgs::identity_for_item(self.tcx, parent),
                             );
 
-                            if check_args_compatible(self.tcx, assoc, impl_args) {
+                            if self.tcx.check_args_compatible(assoc.def_id, impl_args) {
                                 self.tcx
                                     .type_of(assoc.def_id)
                                     .instantiate(self.tcx, impl_args)