Auto merge of #118725 - lcnr:normalizes-to-projection-split-3, r=BoxyUwU

split `NormalizesTo` out of `Projection` 3

third attempt at #112658. Rebasing #116262 is very annoying, so I am doing it again from scratch. We should now be able to merge it without regressing anything as we handle occurs check failures involving aliases correctly since #117088.

see https://hackmd.io/ktEL8knTSYmtdfrMMnA-Hg

fixes https://github.com/rust-lang/trait-system-refactor-initiative/issues/1

r? `@compiler-errors`

8 files changed, 57 insertions, 11 deletions

diff --git a/tests/ui/traits/new-solver/alias-bound-unsound.rs b/tests/ui/traits/new-solver/alias-bound-unsound.rs
index 825e874d71b..907a3010355 100644
--- a/tests/ui/traits/new-solver/alias-bound-unsound.rs
+++ b/tests/ui/traits/new-solver/alias-bound-unsound.rs
@@ -23,7 +23,7 @@ fn main() {
     let x = String::from("hello, world");
     drop(<() as Foo>::copy_me(&x));
     //~^ ERROR overflow evaluating the requirement `<() as Foo>::Item: Sized`
-    //~| ERROR overflow evaluating the requirement `<() as Foo>::Item == _`
+    //~| ERROR overflow evaluating the requirement `<() as Foo>::Item normalizes-to _`
     //~| 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`
diff --git a/tests/ui/traits/new-solver/alias-bound-unsound.stderr b/tests/ui/traits/new-solver/alias-bound-unsound.stderr
index ca4b5c90ff2..29d4d983c03 100644
--- a/tests/ui/traits/new-solver/alias-bound-unsound.stderr
+++ b/tests/ui/traits/new-solver/alias-bound-unsound.stderr
@@ -19,7 +19,7 @@ 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 == _`
+error[E0275]: overflow evaluating the requirement `<() as Foo>::Item normalizes-to _`
   --> $DIR/alias-bound-unsound.rs:24:10
    |
 LL |     drop(<() as Foo>::copy_me(&x));
diff --git a/tests/ui/traits/new-solver/generalize/generalize-proj-new-universe-index-2.rs b/tests/ui/traits/new-solver/generalize/generalize-proj-new-universe-index-2.rs
index 94d645a9859..7fe242f4714 100644
--- a/tests/ui/traits/new-solver/generalize/generalize-proj-new-universe-index-2.rs
+++ b/tests/ui/traits/new-solver/generalize/generalize-proj-new-universe-index-2.rs
@@ -1,5 +1,7 @@
 // compile-flags: -Ztrait-solver=next
 // known-bug: trait-system-refactor-initiative#60
+// dont-check-failure-status
+// dont-check-compiler-stderr
 
 // Generalizing a projection containing an inference variable
 // which cannot be named by the `root_vid` can result in ambiguity.
diff --git a/tests/ui/traits/new-solver/generalize/occurs-check-nested-alias.next.stderr b/tests/ui/traits/new-solver/generalize/occurs-check-nested-alias.next.stderr
index 34c2f0438c7..ad8b24a39c7 100644
--- a/tests/ui/traits/new-solver/generalize/occurs-check-nested-alias.next.stderr
+++ b/tests/ui/traits/new-solver/generalize/occurs-check-nested-alias.next.stderr
@@ -1,9 +1,11 @@
-error[E0271]: type mismatch resolving `<<T as Id<_>>::Id as Unnormalizable>::Assoc == _`
-  --> $DIR/occurs-check-nested-alias.rs:35:9
+error[E0275]: overflow evaluating the requirement `<<T as Id<_>>::Id as Unnormalizable>::Assoc == _`
+  --> $DIR/occurs-check-nested-alias.rs:36:9
    |
 LL |     x = y;
-   |         ^ types differ
+   |         ^
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`occurs_check_nested_alias`)
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0271`.
+For more information about this error, try `rustc --explain E0275`.
diff --git a/tests/ui/traits/new-solver/generalize/occurs-check-nested-alias.rs b/tests/ui/traits/new-solver/generalize/occurs-check-nested-alias.rs
index a2113b2a8b3..02ac091c0a8 100644
--- a/tests/ui/traits/new-solver/generalize/occurs-check-nested-alias.rs
+++ b/tests/ui/traits/new-solver/generalize/occurs-check-nested-alias.rs
@@ -1,7 +1,8 @@
 // revisions: old next
 //[old] check-pass
 
-// Need to emit an alias-relate instead of a `Projection` goal here.
+// Currently always fails to generalize the outer alias, even if it
+// is treated as rigid by `alias-relate`.
 //[next] compile-flags: -Ztrait-solver=next
 //[next] known-bug: trait-system-refactor-initiative#8
 #![crate_type = "lib"]
diff --git a/tests/ui/traits/new-solver/projection/param-env-trait-candidate-1.rs b/tests/ui/traits/new-solver/projection/param-env-trait-candidate-1.rs
new file mode 100644
index 00000000000..e36d574efe2
--- /dev/null
+++ b/tests/ui/traits/new-solver/projection/param-env-trait-candidate-1.rs
@@ -0,0 +1,14 @@
+// check-pass
+// compile-flags: -Ztrait-solver=next
+
+// See https://github.com/rust-lang/trait-system-refactor-initiative/issues/1
+// a minimization of a pattern in core.
+fn next<T: Iterator<Item = U>, U>(t: &mut T) -> Option<U> {
+    t.next()
+}
+
+fn foo<T: Iterator>(t: &mut T) {
+    let _: Option<T::Item> = next(t);
+}
+
+fn main() {}
diff --git a/tests/ui/traits/new-solver/projection/param-env-trait-candidate-2.rs b/tests/ui/traits/new-solver/projection/param-env-trait-candidate-2.rs
new file mode 100644
index 00000000000..c8050997a1d
--- /dev/null
+++ b/tests/ui/traits/new-solver/projection/param-env-trait-candidate-2.rs
@@ -0,0 +1,29 @@
+// check-pass
+// compile-flags: -Ztrait-solver=next
+
+// See https://github.com/rust-lang/trait-system-refactor-initiative/issues/1,
+// a minimization of a pattern in core.
+
+trait Iterator {
+    type Item;
+}
+
+struct Flatten<I>(I);
+
+impl<I, U> Iterator for Flatten<I>
+where
+    I: Iterator<Item = U>,
+{
+    type Item = U;
+}
+
+fn needs_iterator<I: Iterator>() {}
+
+fn environment<J>()
+where
+    J: Iterator,
+{
+    needs_iterator::<Flatten<J>>();
+}
+
+fn main() {}
diff --git a/tests/ui/traits/new-solver/specialization-transmute.stderr b/tests/ui/traits/new-solver/specialization-transmute.stderr
index 18965a465b3..eaf32a475ac 100644
--- a/tests/ui/traits/new-solver/specialization-transmute.stderr
+++ b/tests/ui/traits/new-solver/specialization-transmute.stderr
@@ -8,13 +8,11 @@ LL | #![feature(specialization)]
    = help: consider using `min_specialization` instead, which is more stable and complete
    = note: `#[warn(incomplete_features)]` on by default
 
-error[E0284]: type annotations needed
+error[E0284]: type annotations needed: cannot satisfy `<T as Default>::Id normalizes-to _`
   --> $DIR/specialization-transmute.rs:15:23
    |
 LL |     fn intu(&self) -> &Self::Id {
-   |                       ^^^^^^^^^ cannot infer type
-   |
-   = note: cannot satisfy `<T as Default>::Id == _`
+   |                       ^^^^^^^^^ cannot satisfy `<T as Default>::Id normalizes-to _`
 
 error[E0282]: type annotations needed
   --> $DIR/specialization-transmute.rs:13:23