Auto merge of #90887 - jackh726:issue-90729, r=nikomatsakis

Try to normalize associated types before processing obligations

Closes #90729

r? `@nikomatsakis`

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -346,6 +346,8 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
 
         let obligation = &mut pending_obligation.obligation;
 
+        debug!(?obligation, "process_obligation pre-resolve");
+
         if obligation.predicate.has_infer_types_or_consts() {
             obligation.predicate =
                 self.selcx.infcx().resolve_vars_if_possible(obligation.predicate);
@@ -355,6 +357,21 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
 
         let infcx = self.selcx.infcx();
 
+        if obligation.predicate.has_projections() {
+            let mut obligations = Vec::new();
+            let predicate = crate::traits::project::try_normalize_with_depth_to(
+                self.selcx,
+                obligation.param_env,
+                obligation.cause.clone(),
+                obligation.recursion_depth + 1,
+                obligation.predicate,
+                &mut obligations,
+            );
+            if predicate != obligation.predicate {
+                obligations.push(obligation.with(predicate));
+                return ProcessResult::Changed(mk_pending(obligations));
+            }
+        }
         let binder = obligation.predicate.kind();
         match binder.no_bound_vars() {
             None => match binder.skip_binder() {

compiler/rustc_trait_selection/src/traits/project.rs

@@ -295,6 +295,32 @@ where
     result
 }
 
+#[instrument(level = "info", skip(selcx, param_env, cause, obligations))]
+pub fn try_normalize_with_depth_to<'a, 'b, 'tcx, T>(
+    selcx: &'a mut SelectionContext<'b, 'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    cause: ObligationCause<'tcx>,
+    depth: usize,
+    value: T,
+    obligations: &mut Vec<PredicateObligation<'tcx>>,
+) -> T
+where
+    T: TypeFoldable<'tcx>,
+{
+    debug!(obligations.len = obligations.len());
+    let mut normalizer = AssocTypeNormalizer::new_without_eager_inference_replacement(
+        selcx,
+        param_env,
+        cause,
+        depth,
+        obligations,
+    );
+    let result = ensure_sufficient_stack(|| normalizer.fold(value));
+    debug!(?result, obligations.len = normalizer.obligations.len());
+    debug!(?normalizer.obligations,);
+    result
+}
+
 pub(crate) fn needs_normalization<'tcx, T: TypeFoldable<'tcx>>(value: &T, reveal: Reveal) -> bool {
     match reveal {
         Reveal::UserFacing => value
@@ -314,6 +340,10 @@ struct AssocTypeNormalizer<'a, 'b, 'tcx> {
     obligations: &'a mut Vec<PredicateObligation<'tcx>>,
     depth: usize,
     universes: Vec<Option<ty::UniverseIndex>>,
+    /// If true, when a projection is unable to be completed, an inference
+    /// variable will be created and an obligation registered to project to that
+    /// inference variable. Also, constants will be eagerly evaluated.
+    eager_inference_replacement: bool,
 }
 
 impl<'a, 'b, 'tcx> AssocTypeNormalizer<'a, 'b, 'tcx> {
@@ -324,7 +354,33 @@ impl<'a, 'b, 'tcx> AssocTypeNormalizer<'a, 'b, 'tcx> {
         depth: usize,
         obligations: &'a mut Vec<PredicateObligation<'tcx>>,
     ) -> AssocTypeNormalizer<'a, 'b, 'tcx> {
-        AssocTypeNormalizer { selcx, param_env, cause, obligations, depth, universes: vec![] }
+        AssocTypeNormalizer {
+            selcx,
+            param_env,
+            cause,
+            obligations,
+            depth,
+            universes: vec![],
+            eager_inference_replacement: true,
+        }
+    }
+
+    fn new_without_eager_inference_replacement(
+        selcx: &'a mut SelectionContext<'b, 'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        cause: ObligationCause<'tcx>,
+        depth: usize,
+        obligations: &'a mut Vec<PredicateObligation<'tcx>>,
+    ) -> AssocTypeNormalizer<'a, 'b, 'tcx> {
+        AssocTypeNormalizer {
+            selcx,
+            param_env,
+            cause,
+            obligations,
+            depth,
+            universes: vec![],
+            eager_inference_replacement: false,
+        }
     }
 
     fn fold<T: TypeFoldable<'tcx>>(&mut self, value: T) -> T {
@@ -428,14 +484,28 @@ impl<'a, 'b, 'tcx> TypeFolder<'tcx> for AssocTypeNormalizer<'a, 'b, 'tcx> {
                 // there won't be bound vars there.
 
                 let data = data.super_fold_with(self);
-                let normalized_ty = normalize_projection_type(
-                    self.selcx,
-                    self.param_env,
-                    data,
-                    self.cause.clone(),
-                    self.depth,
-                    &mut self.obligations,
-                );
+                let normalized_ty = if self.eager_inference_replacement {
+                    normalize_projection_type(
+                        self.selcx,
+                        self.param_env,
+                        data,
+                        self.cause.clone(),
+                        self.depth,
+                        &mut self.obligations,
+                    )
+                } else {
+                    opt_normalize_projection_type(
+                        self.selcx,
+                        self.param_env,
+                        data,
+                        self.cause.clone(),
+                        self.depth,
+                        &mut self.obligations,
+                    )
+                    .ok()
+                    .flatten()
+                    .unwrap_or_else(|| ty::Term::Ty(ty.super_fold_with(self)))
+                };
                 debug!(
                     ?self.depth,
                     ?ty,
@@ -501,7 +571,7 @@ impl<'a, 'b, 'tcx> TypeFolder<'tcx> for AssocTypeNormalizer<'a, 'b, 'tcx> {
     }
 
     fn fold_const(&mut self, constant: ty::Const<'tcx>) -> ty::Const<'tcx> {
-        if self.selcx.tcx().lazy_normalization() {
+        if self.selcx.tcx().lazy_normalization() || !self.eager_inference_replacement {
             constant
         } else {
             let constant = constant.super_fold_with(self);

src/test/ui/associated-types/issue-59324.rs

@@ -15,9 +15,9 @@ pub trait ThriftService<Bug: NotFoo>:
 {
     fn get_service(
     //~^ ERROR the trait bound `Bug: Foo` is not satisfied
-    //~| ERROR the trait bound `Bug: Foo` is not satisfied
         &self,
     ) -> Self::AssocType;
+    //~^ the trait bound `Bug: Foo` is not satisfied
 }
 
 fn with_factory<H>(factory: dyn ThriftService<()>) {}

src/test/ui/associated-types/issue-59324.stderr

@@ -6,7 +6,7 @@ LL | |
 LL | |
 LL | |     Service<AssocType = <Bug as Foo>::OnlyFoo>
 ...  |
-LL | |     ) -> Self::AssocType;
+LL | |
 LL | | }
    | |_^ the trait `Foo` is not implemented for `Bug`
    |
@@ -23,7 +23,7 @@ LL | |
 LL | |
 LL | |     Service<AssocType = <Bug as Foo>::OnlyFoo>
 ...  |
-LL | |     ) -> Self::AssocType;
+LL | |
 LL | | }
    | |_^ the trait `Foo` is not implemented for `Bug`
    |
@@ -37,7 +37,6 @@ error[E0277]: the trait bound `Bug: Foo` is not satisfied
    |
 LL | /     fn get_service(
 LL | |
-LL | |
 LL | |         &self,
 LL | |     ) -> Self::AssocType;
    | |_________________________^ the trait `Foo` is not implemented for `Bug`
@@ -48,10 +47,10 @@ LL | pub trait ThriftService<Bug: NotFoo + Foo>:
    |                                     +++++
 
 error[E0277]: the trait bound `Bug: Foo` is not satisfied
-  --> $DIR/issue-59324.rs:16:8
+  --> $DIR/issue-59324.rs:19:10
    |
-LL |     fn get_service(
-   |        ^^^^^^^^^^^ the trait `Foo` is not implemented for `Bug`
+LL |     ) -> Self::AssocType;
+   |          ^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `Bug`
    |
 help: consider further restricting this bound
    |

src/test/ui/generic-associated-types/issue-90729.rs

@@ -0,0 +1,38 @@
+// check-pass
+
+#![feature(generic_associated_types)]
+
+use std::marker::PhantomData;
+
+pub trait Type {
+    type Ref<'a>;
+}
+
+pub trait AsBytes {}
+
+impl AsBytes for &str {}
+
+pub struct Utf8;
+
+impl Type for Utf8 {
+    type Ref<'a> = &'a str;
+}
+
+pub struct Bytes<T: Type> {
+    _marker: PhantomData<T>,
+}
+
+impl<T: Type> Bytes<T>
+where
+    for<'a> T::Ref<'a>: AsBytes,
+{
+    pub fn new() -> Self {
+        Self {
+            _marker: PhantomData,
+        }
+    }
+}
+
+fn main() {
+    let _b = Bytes::<Utf8>::new();
+}

src/test/ui/generic-associated-types/issue-91139.migrate.stderr

@@ -0,0 +1,10 @@
+error[E0311]: the parameter type `T` may not live long enough
+  --> $DIR/issue-91139.rs:27:12
+   |
+LL | fn foo<T>() {
+   |        - help: consider adding an explicit lifetime bound...: `T: 'a`
+LL |     let _: for<'a> fn(<() as Foo<T>>::Type<'a>, &'a T) = |_, _| ();
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
+
+error: aborting due to previous error
+

src/test/ui/generic-associated-types/issue-91139.rs

@@ -1,4 +1,13 @@
-// check-pass
+// revisions: migrate nll
+//[nll]compile-flags: -Z borrowck=mir
+
+// Since we are testing nll (and migration) explicitly as a separate
+// revisions, don't worry about the --compare-mode=nll on this test.
+
+// ignore-compare-mode-nll
+
+//[nll] check-pass
+//[migrate] check-fail
 
 #![feature(generic_associated_types)]
 
@@ -16,6 +25,7 @@ impl<T> Foo<T> for () {
 
 fn foo<T>() {
     let _: for<'a> fn(<() as Foo<T>>::Type<'a>, &'a T) = |_, _| ();
+    //[migrate]~^ the parameter type `T` may not live long enough
 }
 
 pub fn main() {}

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/normalize-under-binder/issue-62529-1.rs

@@ -1,3 +1,5 @@
+// check-pass
+
 // FamilyType (GAT workaround)
 pub trait FamilyLt<'a> {
     type Out;
@@ -78,8 +80,6 @@ where P: Execute + 'static {
 
 fn main() {
     task(annotate(
-        //~^ the size
-        //~^^ the trait bound
         Annotate::<RefMutFamily<usize>>::new(),
         |value: &mut usize| {
             *value = 2;

src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-62529-1.stderr

@@ -1,52 +0,0 @@
-error[E0277]: the size for values of type `impl Execute` cannot be known at compilation time
-  --> $DIR/issue-62529-1.rs:80:10
-   |
-LL |       task(annotate(
-   |  _____----_^
-   | |     |
-   | |     required by a bound introduced by this call
-LL | |
-LL | |
-LL | |         Annotate::<RefMutFamily<usize>>::new(),
-...  |
-LL | |         }
-LL | |     ));
-   | |_____^ doesn't have a size known at compile-time
-   |
-   = help: the trait `Sized` is not implemented for `impl Execute`
-note: required by a bound in `task`
-  --> $DIR/issue-62529-1.rs:69:9
-   |
-LL | fn task<P>(processor: P) -> Task
-   |         ^ required by this bound in `task`
-help: consider relaxing the implicit `Sized` restriction
-   |
-LL | fn task<P: ?Sized>(processor: P) -> Task
-   |          ++++++++
-
-error[E0277]: the trait bound `impl Execute: Execute` is not satisfied
-  --> $DIR/issue-62529-1.rs:80:10
-   |
-LL |       task(annotate(
-   |  _____----_^
-   | |     |
-   | |     required by a bound introduced by this call
-LL | |
-LL | |
-LL | |         Annotate::<RefMutFamily<usize>>::new(),
-...  |
-LL | |         }
-LL | |     ));
-   | |_____^ the trait `Execute` is not implemented for `impl Execute`
-   |
-note: required by a bound in `task`
-  --> $DIR/issue-62529-1.rs:70:10
-   |
-LL | fn task<P>(processor: P) -> Task
-   |    ---- required by a bound in this
-LL | where P: Execute + 'static {
-   |          ^^^^^^^ required by this bound in `task`
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0277`.

src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-71955.migrate.stderr

@@ -1,5 +1,5 @@
 error: implementation of `Parser` is not general enough
-  --> $DIR/issue-71955.rs:57:5
+  --> $DIR/issue-71955.rs:54:5
    |
 LL |     foo(bar, "string", |s| s.len() == 5);
    |     ^^^ implementation of `Parser` is not general enough
@@ -8,43 +8,7 @@ LL |     foo(bar, "string", |s| s.len() == 5);
    = note: ...but it actually implements `Parser<'1>`, for some specific lifetime `'1`
 
 error: implementation of `Parser` is not general enough
-  --> $DIR/issue-71955.rs:57:5
-   |
-LL |     foo(bar, "string", |s| s.len() == 5);
-   |     ^^^ implementation of `Parser` is not general enough
-   |
-   = note: `for<'a> fn(&'a str) -> (&'a str, &'a str) {bar}` must implement `Parser<'0>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Parser<'1>`, for some specific lifetime `'1`
-
-error: implementation of `Parser` is not general enough
-  --> $DIR/issue-71955.rs:57:5
-   |
-LL |     foo(bar, "string", |s| s.len() == 5);
-   |     ^^^ implementation of `Parser` is not general enough
-   |
-   = note: `for<'a> fn(&'a str) -> (&'a str, &'a str) {bar}` must implement `Parser<'0>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Parser<'1>`, for some specific lifetime `'1`
-
-error: implementation of `Parser` is not general enough
-  --> $DIR/issue-71955.rs:57:5
-   |
-LL |     foo(bar, "string", |s| s.len() == 5);
-   |     ^^^ implementation of `Parser` is not general enough
-   |
-   = note: `for<'a> fn(&'a str) -> (&'a str, &'a str) {bar}` must implement `Parser<'0>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Parser<'1>`, for some specific lifetime `'1`
-
-error: implementation of `Parser` is not general enough
-  --> $DIR/issue-71955.rs:57:5
-   |
-LL |     foo(bar, "string", |s| s.len() == 5);
-   |     ^^^ implementation of `Parser` is not general enough
-   |
-   = note: `for<'a> fn(&'a str) -> (&'a str, &'a str) {bar}` must implement `Parser<'0>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Parser<'1>`, for some specific lifetime `'1`
-
-error: implementation of `Parser` is not general enough
-  --> $DIR/issue-71955.rs:63:5
+  --> $DIR/issue-71955.rs:58:5
    |
 LL |     foo(baz, "string", |s| s.0.len() == 5);
    |     ^^^ implementation of `Parser` is not general enough
@@ -52,41 +16,5 @@ LL |     foo(baz, "string", |s| s.0.len() == 5);
    = note: `for<'a> fn(&'a str) -> (&'a str, Wrapper<'a>) {baz}` must implement `Parser<'0>`, for any lifetime `'0`...
    = note: ...but it actually implements `Parser<'1>`, for some specific lifetime `'1`
 
-error: implementation of `Parser` is not general enough
-  --> $DIR/issue-71955.rs:63:5
-   |
-LL |     foo(baz, "string", |s| s.0.len() == 5);
-   |     ^^^ implementation of `Parser` is not general enough
-   |
-   = note: `for<'a> fn(&'a str) -> (&'a str, Wrapper<'a>) {baz}` must implement `Parser<'0>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Parser<'1>`, for some specific lifetime `'1`
-
-error: implementation of `Parser` is not general enough
-  --> $DIR/issue-71955.rs:63:5
-   |
-LL |     foo(baz, "string", |s| s.0.len() == 5);
-   |     ^^^ implementation of `Parser` is not general enough
-   |
-   = note: `for<'a> fn(&'a str) -> (&'a str, Wrapper<'a>) {baz}` must implement `Parser<'0>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Parser<'1>`, for some specific lifetime `'1`
-
-error: implementation of `Parser` is not general enough
-  --> $DIR/issue-71955.rs:63:5
-   |
-LL |     foo(baz, "string", |s| s.0.len() == 5);
-   |     ^^^ implementation of `Parser` is not general enough
-   |
-   = note: `for<'a> fn(&'a str) -> (&'a str, Wrapper<'a>) {baz}` must implement `Parser<'0>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Parser<'1>`, for some specific lifetime `'1`
-
-error: implementation of `Parser` is not general enough
-  --> $DIR/issue-71955.rs:63:5
-   |
-LL |     foo(baz, "string", |s| s.0.len() == 5);
-   |     ^^^ implementation of `Parser` is not general enough
-   |
-   = note: `for<'a> fn(&'a str) -> (&'a str, Wrapper<'a>) {baz}` must implement `Parser<'0>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Parser<'1>`, for some specific lifetime `'1`
-
-error: aborting due to 10 previous errors
+error: aborting due to 2 previous errors
 

src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-71955.nll.stderr

@@ -1,8 +1,79 @@
-error: fatal error triggered by #[rustc_error]
-  --> $DIR/issue-71955.rs:47:1
+error[E0308]: mismatched types
+  --> $DIR/issue-71955.rs:54:5
    |
-LL | fn main() {
-   | ^^^^^^^^^
+LL |     foo(bar, "string", |s| s.len() == 5);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
+   |
+   = note: expected type `for<'r, 's> FnOnce<(&'r &'s str,)>`
+              found type `for<'r> FnOnce<(&'r &str,)>`
+note: this closure does not fulfill the lifetime requirements
+  --> $DIR/issue-71955.rs:54:24
+   |
+LL |     foo(bar, "string", |s| s.len() == 5);
+   |                        ^^^^^^^^^^^^^^^^
+note: the lifetime requirement is introduced here
+  --> $DIR/issue-71955.rs:34:9
+   |
+LL |     F2: FnOnce(&<F1 as Parser>::Output) -> bool
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to previous error
+error[E0308]: mismatched types
+  --> $DIR/issue-71955.rs:54:5
+   |
+LL |     foo(bar, "string", |s| s.len() == 5);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
+   |
+   = note: expected type `FnOnce<(&&str,)>`
+              found type `for<'r> FnOnce<(&'r &str,)>`
+note: this closure does not fulfill the lifetime requirements
+  --> $DIR/issue-71955.rs:54:24
+   |
+LL |     foo(bar, "string", |s| s.len() == 5);
+   |                        ^^^^^^^^^^^^^^^^
+note: the lifetime requirement is introduced here
+  --> $DIR/issue-71955.rs:34:44
+   |
+LL |     F2: FnOnce(&<F1 as Parser>::Output) -> bool
+   |                                            ^^^^
 
+error[E0308]: mismatched types
+  --> $DIR/issue-71955.rs:58:5
+   |
+LL |     foo(baz, "string", |s| s.0.len() == 5);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
+   |
+   = note: expected type `for<'r, 's> FnOnce<(&'r Wrapper<'s>,)>`
+              found type `for<'r> FnOnce<(&'r Wrapper<'_>,)>`
+note: this closure does not fulfill the lifetime requirements
+  --> $DIR/issue-71955.rs:58:24
+   |
+LL |     foo(baz, "string", |s| s.0.len() == 5);
+   |                        ^^^^^^^^^^^^^^^^^^
+note: the lifetime requirement is introduced here
+  --> $DIR/issue-71955.rs:34:9
+   |
+LL |     F2: FnOnce(&<F1 as Parser>::Output) -> bool
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0308]: mismatched types
+  --> $DIR/issue-71955.rs:58:5
+   |
+LL |     foo(baz, "string", |s| s.0.len() == 5);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
+   |
+   = note: expected type `FnOnce<(&Wrapper<'_>,)>`
+              found type `for<'r> FnOnce<(&'r Wrapper<'_>,)>`
+note: this closure does not fulfill the lifetime requirements
+  --> $DIR/issue-71955.rs:58:24
+   |
+LL |     foo(baz, "string", |s| s.0.len() == 5);
+   |                        ^^^^^^^^^^^^^^^^^^
+note: the lifetime requirement is introduced here
+  --> $DIR/issue-71955.rs:34:44
+   |
+LL |     F2: FnOnce(&<F1 as Parser>::Output) -> bool
+   |                                            ^^^^
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-71955.rs

@@ -42,10 +42,7 @@ where
 
 struct Wrapper<'a>(&'a str);
 
-// Because nll currently succeeds and migrate doesn't
-#[rustc_error]
 fn main() {
-    //[nll]~^ fatal
     fn bar<'a>(s: &'a str) -> (&'a str, &'a str) {
         (&s[..1], &s[..])
     }
@@ -56,14 +53,10 @@ fn main() {
 
     foo(bar, "string", |s| s.len() == 5);
     //[migrate]~^ ERROR implementation of `Parser` is not general enough
-    //[migrate]~| ERROR implementation of `Parser` is not general enough
-    //[migrate]~| ERROR implementation of `Parser` is not general enough
-    //[migrate]~| ERROR implementation of `Parser` is not general enough
-    //[migrate]~| ERROR implementation of `Parser` is not general enough
+    //[nll]~^^ ERROR mismatched types
+    //[nll]~| ERROR mismatched types
     foo(baz, "string", |s| s.0.len() == 5);
     //[migrate]~^ ERROR implementation of `Parser` is not general enough
-    //[migrate]~| ERROR implementation of `Parser` is not general enough
-    //[migrate]~| ERROR implementation of `Parser` is not general enough
-    //[migrate]~| ERROR implementation of `Parser` is not general enough
-    //[migrate]~| ERROR implementation of `Parser` is not general enough
+    //[nll]~^^ ERROR mismatched types
+    //[nll]~| ERROR mismatched types
 }

src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-85455.rs

@@ -6,7 +6,8 @@ trait SomeTrait<'a> {
 
 fn give_me_ice<T>() {
     callee::<fn(&()) -> <T as SomeTrait<'_>>::Associated>();
-    //~^ ERROR: the trait bound `T: SomeTrait<'_>` is not satisfied
+    //~^ ERROR the trait bound `T: SomeTrait<'_>` is not satisfied [E0277]
+    //~| ERROR the trait bound `T: SomeTrait<'_>` is not satisfied [E0277]
 }
 
 fn callee<T: Fn<(&'static (),)>>() {

src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-85455.stderr

@@ -9,6 +9,17 @@ help: consider restricting type parameter `T`
 LL | fn give_me_ice<T: SomeTrait<'_>>() {
    |                 +++++++++++++++
 
-error: aborting due to previous error
+error[E0277]: the trait bound `T: SomeTrait<'_>` is not satisfied
+  --> $DIR/issue-85455.rs:8:14
+   |
+LL |     callee::<fn(&()) -> <T as SomeTrait<'_>>::Associated>();
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `SomeTrait<'_>` is not implemented for `T`
+   |
+help: consider restricting type parameter `T`
+   |
+LL | fn give_me_ice<T: SomeTrait<'_>>() {
+   |                 +++++++++++++++
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

src/test/ui/type-alias-impl-trait/generic_duplicate_param_use9.rs

@@ -5,7 +5,7 @@ use std::fmt::Debug;
 fn main() {}
 
 type Two<A, B> = impl Debug;
-//~^ ERROR the trait bound `A: Foo` is not satisfied in `(A, B, <A as Foo>::Bar)`
+//~^ ERROR the trait bound `A: Foo` is not satisfied
 //~| ERROR `A` doesn't implement `Debug`
 //~| ERROR `B` doesn't implement `Debug`
 

src/test/ui/type-alias-impl-trait/generic_duplicate_param_use9.stderr

@@ -10,13 +10,12 @@ note: previous use here
 LL | fn two<T: Debug + Foo, U: Debug>(t: T, u: U) -> Two<T, U> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0277]: the trait bound `A: Foo` is not satisfied in `(A, B, <A as Foo>::Bar)`
+error[E0277]: the trait bound `A: Foo` is not satisfied
   --> $DIR/generic_duplicate_param_use9.rs:7:18
    |
 LL | type Two<A, B> = impl Debug;
-   |                  ^^^^^^^^^^ within `(A, B, <A as Foo>::Bar)`, the trait `Foo` is not implemented for `A`
+   |                  ^^^^^^^^^^ the trait `Foo` is not implemented for `A`
    |
-   = note: required because it appears within the type `(A, B, <A as Foo>::Bar)`
 help: consider restricting type parameter `A`
    |
 LL | type Two<A: Foo, B> = impl Debug;
@@ -28,7 +27,7 @@ error[E0277]: `A` doesn't implement `Debug`
 LL | type Two<A, B> = impl Debug;
    |                  ^^^^^^^^^^ `A` cannot be formatted using `{:?}` because it doesn't implement `Debug`
    |
-   = note: required because of the requirements on the impl of `Debug` for `(A, B, <A as Foo>::Bar)`
+   = note: required because of the requirements on the impl of `Debug` for `(A, B, _)`
 help: consider restricting type parameter `A`
    |
 LL | type Two<A: std::fmt::Debug, B> = impl Debug;
@@ -40,7 +39,7 @@ error[E0277]: `B` doesn't implement `Debug`
 LL | type Two<A, B> = impl Debug;
    |                  ^^^^^^^^^^ `B` cannot be formatted using `{:?}` because it doesn't implement `Debug`
    |
-   = note: required because of the requirements on the impl of `Debug` for `(A, B, <A as Foo>::Bar)`
+   = note: required because of the requirements on the impl of `Debug` for `(A, B, _)`
 help: consider restricting type parameter `B`
    |
 LL | type Two<A, B: std::fmt::Debug> = impl Debug;

src/test/ui/type-alias-impl-trait/issue-89686.rs

@@ -5,8 +5,7 @@
 use std::future::Future;
 
 type G<'a, T> = impl Future<Output = ()>;
-//~^ ERROR: type mismatch resolving `<impl Future<Output = [async output]> as Future>::Output == ()`
-//~| ERROR: the trait bound `T: Trait` is not satisfied
+//~^ ERROR: the trait bound `T: Trait` is not satisfied
 
 trait Trait {
     type F: Future<Output = ()>;

src/test/ui/type-alias-impl-trait/issue-89686.stderr

@@ -1,22 +1,3 @@
-error[E0271]: type mismatch resolving `<impl Future<Output = [async output]> as Future>::Output == ()`
-  --> $DIR/issue-89686.rs:7:17
-   |
-LL | type G<'a, T> = impl Future<Output = ()>;
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found associated type
-...
-LL |         async move { self.f().await }
-   |                    ------------------ the found `async` block
-   |
-  ::: $SRC_DIR/core/src/future/mod.rs:LL:COL
-   |
-LL | pub const fn from_generator<T>(gen: T) -> impl Future<Output = T::Return>
-   |                                           ------------------------------- the found opaque type
-   |
-   = note:    expected unit type `()`
-           found associated type `<impl Future<Output = [async output]> as Future>::Output`
-   = help: consider constraining the associated type `<impl Future<Output = [async output]> as Future>::Output` to `()`
-   = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
-
 error[E0277]: the trait bound `T: Trait` is not satisfied
   --> $DIR/issue-89686.rs:7:17
    |
@@ -28,7 +9,6 @@ help: consider restricting type parameter `T`
 LL | type G<'a, T: Trait> = impl Future<Output = ()>;
    |             +++++++
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors have detailed explanations: E0271, E0277.
-For more information about an error, try `rustc --explain E0271`.
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/unboxed-closures/issue-53448.rs

@@ -1,3 +1,5 @@
+// check-pass
+
 #![feature(unboxed_closures)]
 
 trait Lt<'a> {
@@ -10,6 +12,5 @@ impl<'a> Lt<'a> for () {
 fn main() {
     let v: <() as Lt<'_>>::T = ();
     let f: &mut dyn FnMut<(_,), Output = ()> = &mut |_: <() as Lt<'_>>::T| {};
-    //~^ ERROR: the size for values of type `<() as Lt<'_>>::T` cannot be known
     f(v);
 }

src/test/ui/unboxed-closures/issue-53448.stderr

@@ -1,20 +0,0 @@
-error[E0277]: the size for values of type `<() as Lt<'_>>::T` cannot be known at compilation time
-  --> $DIR/issue-53448.rs:12:54
-   |
-LL |     let f: &mut dyn FnMut<(_,), Output = ()> = &mut |_: <() as Lt<'_>>::T| {};
-   |                                                      ^ doesn't have a size known at compile-time
-   |
-   = help: the trait `Sized` is not implemented for `<() as Lt<'_>>::T`
-   = help: unsized fn params are gated as an unstable feature
-help: consider further restricting the associated type
-   |
-LL | fn main() where <() as Lt<'_>>::T: Sized {
-   |           ++++++++++++++++++++++++++++++
-help: function arguments must have a statically known size, borrowed types always have a known size
-   |
-LL |     let f: &mut dyn FnMut<(_,), Output = ()> = &mut |_: &<() as Lt<'_>>::T| {};
-   |                                                         +
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0277`.