Check GAT, IAT, and weak type where clauses during projection

compiler/rustc_trait_selection/src/solve/inherent_projection.rs

@@ -21,12 +21,6 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             inherent.self_ty(),
             tcx.type_of(impl_def_id).instantiate(tcx, impl_substs),
         )?;
-        self.add_goals(
-            tcx.predicates_of(impl_def_id)
-                .instantiate(tcx, impl_substs)
-                .into_iter()
-                .map(|(pred, _)| goal.with(tcx, pred)),
-        );
 
         // Equate IAT with the RHS of the project goal
         let inherent_substs = inherent.rebase_inherent_args_onto_impl(impl_substs, tcx);
@@ -37,6 +31,14 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         )
         .expect("expected goal term to be fully unconstrained");
 
+        // Check both where clauses on the impl and IAT
+        self.add_goals(
+            tcx.predicates_of(inherent.def_id)
+                .instantiate(tcx, inherent_substs)
+                .into_iter()
+                .map(|(pred, _)| goal.with(tcx, pred)),
+        );
+
         self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
     }
 }

compiler/rustc_trait_selection/src/solve/project_goals.rs

@@ -112,6 +112,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
     ) -> QueryResult<'tcx> {
         if let Some(projection_pred) = assumption.as_projection_clause() {
             if projection_pred.projection_def_id() == goal.predicate.def_id() {
+                let tcx = ecx.tcx();
                 ecx.probe_candidate("assumption").enter(|ecx| {
                     let assumption_projection_pred =
                         ecx.instantiate_binder_with_infer(projection_pred);
@@ -122,6 +123,14 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
                     )?;
                     ecx.eq(goal.param_env, goal.predicate.term, assumption_projection_pred.term)
                         .expect("expected goal term to be fully unconstrained");
+
+                    // Add GAT where clauses from the trait's definition
+                    ecx.add_goals(
+                        tcx.predicates_of(goal.predicate.def_id())
+                            .instantiate_own(tcx, goal.predicate.projection_ty.args)
+                            .map(|(pred, _)| goal.with(tcx, pred)),
+                    );
+
                     then(ecx)
                 })
             } else {
@@ -160,6 +169,13 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
                 .map(|pred| goal.with(tcx, pred));
             ecx.add_goals(where_clause_bounds);
 
+            // Add GAT where clauses from the trait's definition
+            ecx.add_goals(
+                tcx.predicates_of(goal.predicate.def_id())
+                    .instantiate_own(tcx, goal.predicate.projection_ty.args)
+                    .map(|(pred, _)| goal.with(tcx, pred)),
+            );
+
             // In case the associated item is hidden due to specialization, we have to
             // return ambiguity this would otherwise be incomplete, resulting in
             // unsoundness during coherence (#105782).

compiler/rustc_trait_selection/src/solve/weak_types.rs

@@ -14,6 +14,16 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
 
         let actual = tcx.type_of(weak_ty.def_id).instantiate(tcx, weak_ty.args);
         self.eq(goal.param_env, expected, actual)?;
+
+        // Check where clauses
+        self.add_goals(
+            tcx.predicates_of(weak_ty.def_id)
+                .instantiate(tcx, weak_ty.args)
+                .predicates
+                .into_iter()
+                .map(|pred| goal.with(tcx, pred)),
+        );
+
         self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
     }
 }

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1402,9 +1402,17 @@ pub fn compute_inherent_assoc_ty_args<'a, 'b, 'tcx>(
     let impl_def_id = tcx.parent(alias_ty.def_id);
     let impl_args = selcx.infcx.fresh_args_for_item(cause.span, impl_def_id);
 
-    let impl_ty = tcx.type_of(impl_def_id).instantiate(tcx, impl_args);
+    let mut impl_ty = tcx.type_of(impl_def_id).instantiate(tcx, impl_args);
-    let impl_ty =
+    if !selcx.infcx.next_trait_solver() {
-        normalize_with_depth_to(selcx, param_env, cause.clone(), depth + 1, impl_ty, obligations);
+        impl_ty = normalize_with_depth_to(
+            selcx,
+            param_env,
+            cause.clone(),
+            depth + 1,
+            impl_ty,
+            obligations,
+        );
+    }
 
     // Infer the generic parameters of the impl by unifying the
     // impl type with the self type of the projection.

tests/ui/traits/new-solver/alias-bound-unsound.rs

@@ -16,12 +16,17 @@ trait Foo {
 
 impl Foo for () {
     type Item = String where String: Copy;
+    //~^ ERROR overflow evaluating the requirement `<() as Foo>::Item: Copy`
 }
 
 fn main() {
     let x = String::from("hello, world");
     drop(<() as Foo>::copy_me(&x));
-    //~^ ERROR the type `&<() as Foo>::Item` is not well-formed
+    //~^ ERROR overflow evaluating the requirement `<() as Foo>::Item: Sized`
-    //~| ERROR `<() as Foo>::Item` is not well-formed
+    //~| ERROR overflow evaluating the requirement `<() as Foo>::Item == _`
+    //~| ERROR overflow evaluating the requirement `<() as Foo>::Item well-formed`
+    //~| ERROR overflow evaluating the requirement `String <: <() as Foo>::Item`
+    //~| ERROR overflow evaluating the requirement `&<() as Foo>::Item well-formed`
+    //~| ERROR type annotations needed
     println!("{x}");
 }

tests/ui/traits/new-solver/alias-bound-unsound.stderr

@@ -1,14 +1,69 @@
-error: the type `&<() as Foo>::Item` is not well-formed
+error[E0275]: overflow evaluating the requirement `<() as Foo>::Item: Copy`
-  --> $DIR/alias-bound-unsound.rs:23:31
+  --> $DIR/alias-bound-unsound.rs:18:17
+   |
+LL |     type Item = String where String: Copy;
+   |                 ^^^^^^
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`alias_bound_unsound`)
+note: required by a bound in `Foo::Item`
+  --> $DIR/alias-bound-unsound.rs:8:16
+   |
+LL |     type Item: Copy
+   |                ^^^^ required by this bound in `Foo::Item`
+
+error[E0282]: type annotations needed
+  --> $DIR/alias-bound-unsound.rs:24:5
+   |
+LL |     drop(<() as Foo>::copy_me(&x));
+   |     ^^^^ cannot infer type of the type parameter `T` declared on the function `drop`
+   |
+help: consider specifying the generic argument
+   |
+LL |     drop::<T>(<() as Foo>::copy_me(&x));
+   |         +++++
+
+error[E0275]: overflow evaluating the requirement `&<() as Foo>::Item well-formed`
+  --> $DIR/alias-bound-unsound.rs:24:31
    |
 LL |     drop(<() as Foo>::copy_me(&x));
    |                               ^^
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`alias_bound_unsound`)
 
-error: the type `<() as Foo>::Item` is not well-formed
+error[E0275]: overflow evaluating the requirement `String <: <() as Foo>::Item`
-  --> $DIR/alias-bound-unsound.rs:23:10
+  --> $DIR/alias-bound-unsound.rs:24:31
+   |
+LL |     drop(<() as Foo>::copy_me(&x));
+   |                               ^^
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`alias_bound_unsound`)
+
+error[E0275]: overflow evaluating the requirement `<() as Foo>::Item well-formed`
+  --> $DIR/alias-bound-unsound.rs:24:10
    |
 LL |     drop(<() as Foo>::copy_me(&x));
    |          ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`alias_bound_unsound`)
 
-error: aborting due to 2 previous errors
+error[E0275]: overflow evaluating the requirement `<() as Foo>::Item == _`
+  --> $DIR/alias-bound-unsound.rs:24:10
+   |
+LL |     drop(<() as Foo>::copy_me(&x));
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`alias_bound_unsound`)
 
+error[E0275]: overflow evaluating the requirement `<() as Foo>::Item: Sized`
+  --> $DIR/alias-bound-unsound.rs:24:10
+   |
+LL |     drop(<() as Foo>::copy_me(&x));
+   |          ^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`alias_bound_unsound`)
+   = note: the return type of a function must have a statically known size
+
+error: aborting due to 7 previous errors
+
+Some errors have detailed explanations: E0275, E0282.
+For more information about an error, try `rustc --explain E0275`.