Normalize possibly un-normalized GAT projections

compiler/rustc_infer/src/infer/type_variable.rs

@@ -259,7 +259,7 @@ impl<'tcx> TypeVariableTable<'_, 'tcx> {
         let index = self.values().push(TypeVariableData { origin });
         assert_eq!(eq_key.vid.as_u32(), index as u32);
 
-        debug!("new_var(index={:?}, universe={:?}, origin={:?}", eq_key.vid, universe, origin,);
+        debug!("new_var(index={:?}, universe={:?}, origin={:?})", eq_key.vid, universe, origin);
 
         eq_key.vid
     }

compiler/rustc_trait_selection/src/traits/project.rs

@@ -213,7 +213,18 @@ fn project_and_unify_type<'cx, 'tcx>(
 
     let infcx = selcx.infcx();
     // FIXME(associated_const_equality): Handle consts here as well as types.
-    let obligation_pred_ty = obligation.predicate.term.ty().unwrap();
+    // FIXME(compiler-errors): We need to normalize here until we properly handle
+    // GAT projection types that we can't normalize properly, see note in
+    // `rustc_trait_selection::traits::project`
+    let obligation_pred_ty = normalize_with_depth_to(
+        selcx,
+        obligation.param_env,
+        obligation.cause.clone(),
+        obligation.recursion_depth + 1,
+        obligation.predicate.term.ty().unwrap(),
+        &mut obligations,
+    );
+
     match infcx.at(&obligation.cause, obligation.param_env).eq(normalized_ty, obligation_pred_ty) {
         Ok(InferOk { obligations: inferred_obligations, value: () }) => {
             obligations.extend(inferred_obligations);

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

@@ -555,23 +555,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         )
         .map_bound(|(trait_ref, _)| trait_ref);
 
-        let Normalized { value: trait_ref, mut obligations } = ensure_sufficient_stack(|| {
-            normalize_with_depth(
-                self,
-                obligation.param_env,
-                obligation.cause.clone(),
-                obligation.recursion_depth + 1,
-                trait_ref,
-            )
-        });
-
-        obligations.extend(self.confirm_poly_trait_refs(
-            obligation.cause.clone(),
-            obligation.param_env,
-            obligation.predicate.to_poly_trait_ref(),
-            trait_ref,
-        )?);
-        Ok(ImplSourceFnPointerData { fn_ty: self_ty, nested: obligations })
+        let nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
+        Ok(ImplSourceFnPointerData { fn_ty: self_ty, nested })
     }
 
     fn confirm_trait_alias_candidate(
@@ -618,26 +603,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         debug!(?obligation, ?generator_def_id, ?substs, "confirm_generator_candidate");
 
         let trait_ref = self.generator_trait_ref_unnormalized(obligation, substs);
-        let Normalized { value: trait_ref, mut obligations } = ensure_sufficient_stack(|| {
-            normalize_with_depth(
-                self,
-                obligation.param_env,
-                obligation.cause.clone(),
-                obligation.recursion_depth + 1,
-                trait_ref,
-            )
-        });
 
-        debug!(?trait_ref, ?obligations, "generator candidate obligations");
-
-        obligations.extend(self.confirm_poly_trait_refs(
-            obligation.cause.clone(),
-            obligation.param_env,
-            obligation.predicate.to_poly_trait_ref(),
-            trait_ref,
-        )?);
+        let nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
+        debug!(?trait_ref, ?nested, "generator candidate obligations");
 
-        Ok(ImplSourceGeneratorData { generator_def_id, substs, nested: obligations })
+        Ok(ImplSourceGeneratorData { generator_def_id, substs, nested })
     }
 
     #[instrument(skip(self), level = "debug")]
@@ -659,52 +629,23 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             _ => bug!("closure candidate for non-closure {:?}", obligation),
         };
 
-        let obligation_predicate = obligation.predicate;
-        let Normalized { value: obligation_predicate, mut obligations } =
-            ensure_sufficient_stack(|| {
-                normalize_with_depth(
-                    self,
-                    obligation.param_env,
-                    obligation.cause.clone(),
-                    obligation.recursion_depth + 1,
-                    obligation_predicate,
-                )
-            });
-
         let trait_ref = self.closure_trait_ref_unnormalized(obligation, substs);
-        let Normalized { value: trait_ref, obligations: trait_ref_obligations } =
-            ensure_sufficient_stack(|| {
-                normalize_with_depth(
-                    self,
-                    obligation.param_env,
-                    obligation.cause.clone(),
-                    obligation.recursion_depth + 1,
-                    trait_ref,
-                )
-            });
+        let mut nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
 
-        debug!(?closure_def_id, ?trait_ref, ?obligations, "confirm closure candidate obligations");
-
-        obligations.extend(trait_ref_obligations);
-        obligations.extend(self.confirm_poly_trait_refs(
-            obligation.cause.clone(),
-            obligation.param_env,
-            obligation_predicate.to_poly_trait_ref(),
-            trait_ref,
-        )?);
+        debug!(?closure_def_id, ?trait_ref, ?nested, "confirm closure candidate obligations");
 
         // FIXME: Chalk
 
         if !self.tcx().sess.opts.debugging_opts.chalk {
-            obligations.push(Obligation::new(
+            nested.push(Obligation::new(
                 obligation.cause.clone(),
                 obligation.param_env,
                 ty::Binder::dummy(ty::PredicateKind::ClosureKind(closure_def_id, substs, kind))
                     .to_predicate(self.tcx()),
             ));
         }
 
-        Ok(ImplSourceClosureData { closure_def_id, substs, nested: obligations })
+        Ok(ImplSourceClosureData { closure_def_id, substs, nested })
     }
 
     /// In the case of closure types and fn pointers,
@@ -735,15 +676,31 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     #[instrument(skip(self), level = "trace")]
     fn confirm_poly_trait_refs(
         &mut self,
-        obligation_cause: ObligationCause<'tcx>,
-        obligation_param_env: ty::ParamEnv<'tcx>,
-        obligation_trait_ref: ty::PolyTraitRef<'tcx>,
+        obligation: &TraitObligation<'tcx>,
         expected_trait_ref: ty::PolyTraitRef<'tcx>,
     ) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
+        let obligation_trait_ref = obligation.predicate.to_poly_trait_ref();
+        // Normalize the obligation and expected trait refs together, because why not
+        let Normalized { obligations: nested, value: (obligation_trait_ref, expected_trait_ref) } =
+            ensure_sufficient_stack(|| {
+                self.infcx.commit_unconditionally(|_| {
+                    normalize_with_depth(
+                        self,
+                        obligation.param_env,
+                        obligation.cause.clone(),
+                        obligation.recursion_depth + 1,
+                        (obligation_trait_ref, expected_trait_ref),
+                    )
+                })
+            });
+
         self.infcx
-            .at(&obligation_cause, obligation_param_env)
+            .at(&obligation.cause, obligation.param_env)
             .sup(obligation_trait_ref, expected_trait_ref)
-            .map(|InferOk { obligations, .. }| obligations)
+            .map(|InferOk { mut obligations, .. }| {
+                obligations.extend(nested);
+                obligations
+            })
             .map_err(|e| OutputTypeParameterMismatch(expected_trait_ref, obligation_trait_ref, e))
     }
 

src/test/ui/generic-associated-types/issue-93341.rs

@@ -0,0 +1,55 @@
+// check-pass
+
+#![feature(generic_associated_types)]
+use std::marker::PhantomData;
+
+pub struct Id<'id>(PhantomData<fn(&'id ()) -> &'id ()>);
+
+fn new_id() -> Id<'static> {
+    Id(PhantomData)
+}
+
+pub trait HasLifetime where {
+    type AtLifetime<'a>;
+}
+
+pub struct ExistentialLifetime<S: HasLifetime>(S::AtLifetime<'static>);
+
+impl<S: HasLifetime> ExistentialLifetime<S> {
+    pub fn new<F>(f: F) -> ExistentialLifetime<S>
+        where for<'id> F: FnOnce(Id<'id>) -> S::AtLifetime<'id> {
+        ExistentialLifetime(f(new_id()))
+    }
+}
+
+
+struct ExampleS<'id>(Id<'id>);
+
+struct ExampleMarker;
+
+impl HasLifetime for ExampleMarker {
+    type AtLifetime<'id> = ExampleS<'id>;
+}
+
+
+fn broken0() -> ExistentialLifetime<ExampleMarker> {
+    fn new_helper<'id>(id: Id<'id>) -> ExampleS<'id> {
+        ExampleS(id)
+    }
+
+    ExistentialLifetime::<ExampleMarker>::new(new_helper)
+}
+
+fn broken1() -> ExistentialLifetime<ExampleMarker> {
+    fn new_helper<'id>(id: Id<'id>) -> <ExampleMarker as HasLifetime>::AtLifetime<'id> {
+        ExampleS(id)
+    }
+
+    ExistentialLifetime::<ExampleMarker>::new(new_helper)
+}
+
+fn broken2() -> ExistentialLifetime<ExampleMarker> {
+    ExistentialLifetime::<ExampleMarker>::new(|id| ExampleS(id))
+}
+
+fn main() {}

src/test/ui/generic-associated-types/issue-93342.rs

@@ -0,0 +1,57 @@
+// check-pass
+
+#![feature(generic_associated_types)]
+
+use std::marker::PhantomData;
+
+pub trait Scalar: 'static {
+    type RefType<'a>: ScalarRef<'a>;
+}
+
+pub trait ScalarRef<'a>: 'a {}
+
+impl Scalar for i32 {
+    type RefType<'a> = i32;
+}
+
+impl Scalar for String {
+    type RefType<'a> = &'a str;
+}
+
+impl Scalar for bool {
+    type RefType<'a> = i32;
+}
+
+impl<'a> ScalarRef<'a> for bool {}
+
+impl<'a> ScalarRef<'a> for i32 {}
+
+impl<'a> ScalarRef<'a> for &'a str {}
+
+fn str_contains(a: &str, b: &str) -> bool {
+    a.contains(b)
+}
+
+pub struct BinaryExpression<A: Scalar, B: Scalar, O: Scalar, F>
+where
+    F: Fn(A::RefType<'_>, B::RefType<'_>) -> O,
+{
+    f: F,
+    _phantom: PhantomData<(A, B, O)>,
+}
+
+impl<A: Scalar, B: Scalar, O: Scalar, F> BinaryExpression<A, B, O, F>
+where
+    F: Fn(A::RefType<'_>, B::RefType<'_>) -> O,
+{
+    pub fn new(f: F) -> Self {
+        Self {
+            f,
+            _phantom: PhantomData,
+        }
+    }
+}
+
+fn main() {
+    BinaryExpression::<String, String, bool, _>::new(str_contains);
+}

src/test/ui/higher-rank-trait-bounds/issue-60283.rs

@@ -1,3 +1,5 @@
+// check-pass
+
 pub trait Trait<'a> {
     type Item;
 }
@@ -15,6 +17,4 @@ where
 
 fn main() {
     foo((), drop)
-    //~^ ERROR type mismatch in function arguments
-    //~| ERROR size for values of type `<() as Trait<'_>>::Item` cannot be known at compilation time
 }

src/test/ui/hrtb/issue-62203-hrtb-ice.rs

@@ -36,7 +36,6 @@ trait Ty<'a> {
 
 fn main() {
     let v = Unit2.m(
-        //~^ ERROR type mismatch
         L {
         //~^ ERROR type mismatch
             f : |x| { drop(x); Unit4 }