trait_sel: no norm of preds of projections

So that some of the previous tests start passing again, it required
removing normalisation of the predicates of projections when
confirming projection candidates. This permits more uses of GATs and
changes the output of yet more tests.

Author: davidtwco

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

@@ -144,8 +144,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         obligation: &PolyTraitObligation<'tcx>,
         idx: usize,
     ) -> Result<PredicateObligations<'tcx>, SelectionError<'tcx>> {
-        let tcx = self.tcx();
-
         let placeholder_trait_predicate =
             self.infcx.enter_forall_and_leak_universe(obligation.predicate).trait_ref;
         let placeholder_self_ty = self.infcx.shallow_resolve(placeholder_trait_predicate.self_ty());
@@ -194,28 +192,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 .map_err(|_| SelectionError::Unimplemented)?,
         );
 
-        // FIXME(compiler-errors): I don't think this is needed.
-        if let ty::Alias(ty::Projection, alias_ty) = placeholder_self_ty.kind() {
-            let predicates = tcx.predicates_of(alias_ty.def_id).instantiate_own(tcx, alias_ty.args);
-            for (predicate, _) in predicates {
-                let normalized = normalize_with_depth_to(
-                    self,
-                    obligation.param_env,
-                    obligation.cause.clone(),
-                    obligation.recursion_depth + 1,
-                    predicate,
-                    &mut obligations,
-                );
-                obligations.push(Obligation::with_depth(
-                    self.tcx(),
-                    obligation.cause.clone(),
-                    obligation.recursion_depth + 1,
-                    obligation.param_env,
-                    normalized,
-                ));
-            }
-        }
-
         Ok(obligations)
     }
 

tests/ui/dyn-compatibility/assoc_type_bounds_sized_used.rs

@@ -9,7 +9,8 @@ trait Bop {
 
 fn bop<T: Bop + ?Sized>() {
     let _ = <T as Bop>::Bar::default();
-    //~^ ERROR: trait bounds were not satisfied
+    //~^ ERROR: the size for values of type `T` cannot be known at compilation time
+    //~| ERROR: the size for values of type `T` cannot be known at compilation time
     //~| ERROR: the size for values of type `T` cannot be known at compilation time
 }
 

tests/ui/dyn-compatibility/assoc_type_bounds_sized_used.stderr

@@ -24,21 +24,58 @@ help: consider relaxing the implicit `Sized` restriction
 LL |     type Bar: Default + ?Sized
    |                       ++++++++
 
-error[E0599]: the function or associated item `default` exists for associated type `<T as Bop>::Bar`, but its trait bounds were not satisfied
-  --> $DIR/assoc_type_bounds_sized_used.rs:11:30
+error[E0277]: the size for values of type `T` cannot be known at compilation time
+  --> $DIR/assoc_type_bounds_sized_used.rs:11:13
    |
+LL | fn bop<T: Bop + ?Sized>() {
+   |        - this type parameter needs to be `Sized`
 LL |     let _ = <T as Bop>::Bar::default();
-   |                              ^^^^^^^ function or associated item cannot be called on `<T as Bop>::Bar` due to unsatisfied trait bounds
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+note: required by a bound in `Bop::Bar`
+  --> $DIR/assoc_type_bounds_sized_used.rs:7:15
+   |
+LL |     type Bar: Default
+   |          --- required by a bound in this associated type
+LL |     where
+LL |         Self: Sized;
+   |               ^^^^^ required by this bound in `Bop::Bar`
+help: consider removing the `?Sized` bound to make the type parameter `Sized`
+   |
+LL - fn bop<T: Bop + ?Sized>() {
+LL + fn bop<T: Bop>() {
    |
-   = note: the following trait bounds were not satisfied:
-           `T: Sized`
-           which is required by `<T as Bop>::Bar: Default`
-help: consider restricting the type parameter to satisfy the trait bound
+help: consider relaxing the implicit `Sized` restriction
+   |
+LL |     type Bar: Default + ?Sized
+   |                       ++++++++
+
+error[E0277]: the size for values of type `T` cannot be known at compilation time
+  --> $DIR/assoc_type_bounds_sized_used.rs:11:13
    |
-LL | fn bop<T: Bop + ?Sized>() where T: Sized {
-   |                           ++++++++++++++
+LL | fn bop<T: Bop + ?Sized>() {
+   |        - this type parameter needs to be `Sized`
+LL |     let _ = <T as Bop>::Bar::default();
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+note: required by a bound in `Bop::Bar`
+  --> $DIR/assoc_type_bounds_sized_used.rs:7:15
+   |
+LL |     type Bar: Default
+   |          --- required by a bound in this associated type
+LL |     where
+LL |         Self: Sized;
+   |               ^^^^^ required by this bound in `Bop::Bar`
+help: consider removing the `?Sized` bound to make the type parameter `Sized`
+   |
+LL - fn bop<T: Bop + ?Sized>() {
+LL + fn bop<T: Bop>() {
+   |
+help: consider relaxing the implicit `Sized` restriction
+   |
+LL |     type Bar: Default + ?Sized
+   |                       ++++++++
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0277, E0599.
-For more information about an error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0277`.

tests/ui/generic-associated-types/bugs/issue-100013.stderr

@@ -1,25 +1,3 @@
-error: lifetime bound not satisfied
-  --> $DIR/issue-100013.rs:15:5
-   |
-LL | /     async { // a coroutine checked for autotrait impl `Send`
-LL | |         let x = None::<I::Future<'_, '_>>; // a type referencing GAT
-LL | |         async {}.await; // a yield point
-LL | |     }
-   | |_____^
-   |
-   = note: this is a known limitation that will be removed in the future (see issue #100013 <https://github.com/rust-lang/rust/issues/100013> for more information)
-
-error: lifetime bound not satisfied
-  --> $DIR/issue-100013.rs:22:5
-   |
-LL | /     async { // a coroutine checked for autotrait impl `Send`
-LL | |         let x = None::<I::Future<'a, 'b>>; // a type referencing GAT
-LL | |         async {}.await; // a yield point
-LL | |     }
-   | |_____^
-   |
-   = note: this is a known limitation that will be removed in the future (see issue #100013 <https://github.com/rust-lang/rust/issues/100013> for more information)
-
 error: lifetime may not live long enough
   --> $DIR/issue-100013.rs:23:17
    |
@@ -33,16 +11,5 @@ LL |         let x = None::<I::Future<'a, 'b>>; // a type referencing GAT
    |
    = help: consider adding the following bound: `'a: 'b`
 
-error: lifetime bound not satisfied
-  --> $DIR/issue-100013.rs:29:5
-   |
-LL | /     async { // a coroutine checked for autotrait impl `Send`
-LL | |         let x = None::<I::Future<'a, 'b>>; // a type referencing GAT
-LL | |         async {}.await; // a yield point
-LL | |     }
-   | |_____^
-   |
-   = note: this is a known limitation that will be removed in the future (see issue #100013 <https://github.com/rust-lang/rust/issues/100013> for more information)
-
-error: aborting due to 4 previous errors
+error: aborting due to 1 previous error
 

tests/ui/generic-associated-types/issue-92096.rs

@@ -1,3 +1,4 @@
+//@ check-pass
 //@ edition:2018
 
 use std::future::Future;
@@ -15,14 +16,6 @@ where
     C: Client + Send + Sync,
 {
     async move { c.connect().await }
-    //~^ ERROR `C` does not live long enough
-    //
-    // FIXME(#71723). This is because we infer at some point a value of
-    //
-    // impl Future<Output = <C as Client>::Connection<'_>>
-    //
-    // and then we somehow fail the WF check because `where C: 'a` is not known,
-    // but I'm not entirely sure how that comes about.
 }
 
 fn main() {}

tests/ui/generic-associated-types/issue-92096.stderr

@@ -1,4 +1,4 @@
-//@ check-fail
+//@ check-pass
 
 pub trait Trait {
     type Assoc<'a> where Self: 'a;
@@ -11,7 +11,7 @@ where
 
 pub struct Type;
 
-impl<T: Trait> Foo<T> for Type //~ ERROR: the parameter type `T` may not live long enough
+impl<T: Trait> Foo<T> for Type
 where
     for<'a> T::Assoc<'a>: Clone
 {}

tests/ui/generic-associated-types/issue-93262.rs

@@ -0,0 +1,21 @@
+//@ check-pass
+//@ compile-flags: --crate-type=lib
+//@ revisions: old next
+//@[next] compile-flags: -Znext-solver
+
+use std::marker::PhantomData;
+
+pub trait ZeroMapKV<'a> {
+    type Container;
+}
+
+pub trait ZeroFrom<'zf, C: ?Sized> {}
+
+pub struct ZeroMap<'a, K: ZeroMapKV<'a>>(PhantomData<&'a K>);
+
+impl<'zf, 's, K> ZeroFrom<'zf, ZeroMap<'s, K>> for ZeroMap<'zf, K>
+where
+    K: for<'b> ZeroMapKV<'b>,
+    <K as ZeroMapKV<'zf>>::Container: ZeroFrom<'zf, <K as ZeroMapKV<'s>>::Container>,
+{
+}