Auto merge of #125203 - matthiaskrgr:rollup-5pv7drz, r=matthiaskrgr

Rollup of 5 pull requests

Successful merges:

 - #123694 (expand: fix minor diagnostics bug)
 - #125171 (Rename `flatten(_mut)` → `as_flattened(_mut)`)
 - #125181 (set `rust.channel` properly in source tarballs)
 - #125186 (Remove duplicate word from addr docs)
 - #125191 (Report better WF obligation leaf obligations in new solver)

r? `@ghost`
`@rustbot` modify labels: rollup

25 files changed, 183 insertions, 126 deletions

diff --git a/compiler/rustc_expand/messages.ftl b/compiler/rustc_expand/messages.ftl
index 7ae988a5be6..530b37aadb1 100644
--- a/compiler/rustc_expand/messages.ftl
+++ b/compiler/rustc_expand/messages.ftl
@@ -10,6 +10,11 @@ expand_attribute_meta_item =
 expand_attribute_single_word =
     attribute must only be a single word
 
+expand_attributes_on_expressions_experimental =
+    attributes on expressions are experimental
+    .help_outer_doc = `///` is used for outer documentation comments; for a plain comment, use `//`
+    .help_inner_doc = `//!` is used for inner documentation comments; for a plain comment, use `//` by removing the `!` or inserting a space in between them: `// !`
+
 expand_attributes_wrong_form =
     attribute must be of form: `attributes(foo, bar)`
 
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
index 67a5a9128cc..35f0d8abffc 100644
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@@ -382,7 +382,6 @@ impl<'a> StripUnconfigured<'a> {
     }
 
     /// If attributes are not allowed on expressions, emit an error for `attr`
-    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
     #[instrument(level = "trace", skip(self))]
     pub(crate) fn maybe_emit_expr_attr_err(&self, attr: &Attribute) {
         if self.features.is_some_and(|features| !features.stmt_expr_attributes)
@@ -392,11 +391,15 @@ impl<'a> StripUnconfigured<'a> {
                 &self.sess,
                 sym::stmt_expr_attributes,
                 attr.span,
-                "attributes on expressions are experimental",
+                crate::fluent_generated::expand_attributes_on_expressions_experimental,
             );
 
             if attr.is_doc_comment() {
-                err.help("`///` is for documentation comments. For a plain comment, use `//`.");
+                err.help(if attr.style == AttrStyle::Outer {
+                    crate::fluent_generated::expand_help_outer_doc
+                } else {
+                    crate::fluent_generated::expand_help_inner_doc
+                });
             }
 
             err.emit();
diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs
index 3379c1d51a8..625bcf33a16 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/solve/fulfill.rs
@@ -384,39 +384,64 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
             return ControlFlow::Break(self.obligation.clone());
         }
 
-        // FIXME: Could we extract a trait ref from a projection here too?
+        let tcx = goal.infcx().tcx;
         // FIXME: Also, what about considering >1 layer up the stack? May be necessary
         // for normalizes-to.
-        let Some(parent_trait_pred) = goal.goal().predicate.to_opt_poly_trait_pred() else {
-            return ControlFlow::Break(self.obligation.clone());
+        let pred_kind = goal.goal().predicate.kind();
+        let child_mode = match pred_kind.skip_binder() {
+            ty::PredicateKind::Clause(ty::ClauseKind::Trait(parent_trait_pred)) => {
+                ChildMode::Trait(pred_kind.rebind(parent_trait_pred))
+            }
+            ty::PredicateKind::NormalizesTo(normalizes_to)
+                if matches!(
+                    normalizes_to.alias.kind(tcx),
+                    ty::AliasTermKind::ProjectionTy | ty::AliasTermKind::ProjectionConst
+                ) =>
+            {
+                ChildMode::Trait(pred_kind.rebind(ty::TraitPredicate {
+                    trait_ref: normalizes_to.alias.trait_ref(tcx),
+                    polarity: ty::PredicatePolarity::Positive,
+                }))
+            }
+            ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(_)) => {
+                ChildMode::WellFormedObligation
+            }
+            _ => {
+                return ControlFlow::Break(self.obligation.clone());
+            }
         };
 
-        let tcx = goal.infcx().tcx;
         let mut impl_where_bound_count = 0;
         for nested_goal in candidate.instantiate_nested_goals(self.span()) {
+            let make_obligation = |cause| Obligation {
+                cause,
+                param_env: nested_goal.goal().param_env,
+                predicate: nested_goal.goal().predicate,
+                recursion_depth: self.obligation.recursion_depth + 1,
+            };
+
             let obligation;
-            match nested_goal.source() {
-                GoalSource::Misc => {
+            match (child_mode, nested_goal.source()) {
+                (ChildMode::Trait(_), GoalSource::Misc) => {
                     continue;
                 }
-                GoalSource::ImplWhereBound => {
-                    obligation = Obligation {
-                        cause: derive_cause(
-                            tcx,
-                            candidate.kind(),
-                            self.obligation.cause.clone(),
-                            impl_where_bound_count,
-                            parent_trait_pred,
-                        ),
-                        param_env: nested_goal.goal().param_env,
-                        predicate: nested_goal.goal().predicate,
-                        recursion_depth: self.obligation.recursion_depth + 1,
-                    };
+                (ChildMode::Trait(parent_trait_pred), GoalSource::ImplWhereBound) => {
+                    obligation = make_obligation(derive_cause(
+                        tcx,
+                        candidate.kind(),
+                        self.obligation.cause.clone(),
+                        impl_where_bound_count,
+                        parent_trait_pred,
+                    ));
                     impl_where_bound_count += 1;
                 }
-                GoalSource::InstantiateHigherRanked => {
+                // Skip over a higher-ranked predicate.
+                (_, GoalSource::InstantiateHigherRanked) => {
                     obligation = self.obligation.clone();
                 }
+                (ChildMode::WellFormedObligation, _) => {
+                    obligation = make_obligation(self.obligation.cause.clone());
+                }
             }
 
             // Skip nested goals that aren't the *reason* for our goal's failure.
@@ -436,6 +461,18 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
     }
 }
 
+#[derive(Copy, Clone)]
+enum ChildMode<'tcx> {
+    // Try to derive an `ObligationCause::{ImplDerived,BuiltinDerived}`,
+    // and skip all `GoalSource::Misc`, which represent useless obligations
+    // such as alias-eq which may not hold.
+    Trait(ty::PolyTraitPredicate<'tcx>),
+    // Skip trying to derive an `ObligationCause` from this obligation, and
+    // report *all* sub-obligations as if they came directly from the parent
+    // obligation.
+    WellFormedObligation,
+}
+
 fn derive_cause<'tcx>(
     tcx: TyCtxt<'tcx>,
     candidate_kind: ProbeKind<'tcx>,
diff --git a/library/core/src/ptr/mut_ptr.rs b/library/core/src/ptr/mut_ptr.rs
index b67930503e0..7856a1d8581 100644
--- a/library/core/src/ptr/mut_ptr.rs
+++ b/library/core/src/ptr/mut_ptr.rs
@@ -187,7 +187,7 @@ impl<T: ?Sized> *mut T {
     ///
     /// This is similar to `self as usize`, which semantically discards *provenance* and
     /// *address-space* information. However, unlike `self as usize`, casting the returned address
-    /// back to a pointer yields yields a [pointer without provenance][without_provenance_mut], which is undefined
+    /// back to a pointer yields a [pointer without provenance][without_provenance_mut], which is undefined
     /// behavior to dereference. To properly restore the lost information and obtain a
     /// dereferenceable pointer, use [`with_addr`][pointer::with_addr] or
     /// [`map_addr`][pointer::map_addr].
diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index 9bee50424b3..f82f965e67c 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -4533,21 +4533,21 @@ impl<T, const N: usize> [[T; N]] {
     /// ```
     /// #![feature(slice_flatten)]
     ///
-    /// assert_eq!([[1, 2, 3], [4, 5, 6]].flatten(), &[1, 2, 3, 4, 5, 6]);
+    /// assert_eq!([[1, 2, 3], [4, 5, 6]].as_flattened(), &[1, 2, 3, 4, 5, 6]);
     ///
     /// assert_eq!(
-    ///     [[1, 2, 3], [4, 5, 6]].flatten(),
-    ///     [[1, 2], [3, 4], [5, 6]].flatten(),
+    ///     [[1, 2, 3], [4, 5, 6]].as_flattened(),
+    ///     [[1, 2], [3, 4], [5, 6]].as_flattened(),
     /// );
     ///
     /// let slice_of_empty_arrays: &[[i32; 0]] = &[[], [], [], [], []];
-    /// assert!(slice_of_empty_arrays.flatten().is_empty());
+    /// assert!(slice_of_empty_arrays.as_flattened().is_empty());
     ///
     /// let empty_slice_of_arrays: &[[u32; 10]] = &[];
-    /// assert!(empty_slice_of_arrays.flatten().is_empty());
+    /// assert!(empty_slice_of_arrays.as_flattened().is_empty());
     /// ```
     #[unstable(feature = "slice_flatten", issue = "95629")]
-    pub const fn flatten(&self) -> &[T] {
+    pub const fn as_flattened(&self) -> &[T] {
         let len = if T::IS_ZST {
             self.len().checked_mul(N).expect("slice len overflow")
         } else {
@@ -4581,11 +4581,11 @@ impl<T, const N: usize> [[T; N]] {
     /// }
     ///
     /// let mut array = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
-    /// add_5_to_all(array.flatten_mut());
+    /// add_5_to_all(array.as_flattened_mut());
     /// assert_eq!(array, [[6, 7, 8], [9, 10, 11], [12, 13, 14]]);
     /// ```
     #[unstable(feature = "slice_flatten", issue = "95629")]
-    pub fn flatten_mut(&mut self) -> &mut [T] {
+    pub fn as_flattened_mut(&mut self) -> &mut [T] {
         let len = if T::IS_ZST {
             self.len().checked_mul(N).expect("slice len overflow")
         } else {
diff --git a/library/core/tests/slice.rs b/library/core/tests/slice.rs
index ffe8ffcc7f2..c91ac2fbb43 100644
--- a/library/core/tests/slice.rs
+++ b/library/core/tests/slice.rs
@@ -2609,14 +2609,14 @@ fn test_slice_from_ptr_range() {
 #[should_panic = "slice len overflow"]
 fn test_flatten_size_overflow() {
     let x = &[[(); usize::MAX]; 2][..];
-    let _ = x.flatten();
+    let _ = x.as_flattened();
 }
 
 #[test]
 #[should_panic = "slice len overflow"]
 fn test_flatten_mut_size_overflow() {
     let x = &mut [[(); usize::MAX]; 2][..];
-    let _ = x.flatten_mut();
+    let _ = x.as_flattened_mut();
 }
 
 #[test]
diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index 8713eb304d2..19119a073c5 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -1307,6 +1307,9 @@ impl Config {
             toml_path = config.src.join(toml_path);
         }
 
+        let file_content = t!(fs::read_to_string(config.src.join("src/ci/channel")));
+        let ci_channel = file_content.trim_end();
+
         // Give a hard error if `--config` or `RUST_BOOTSTRAP_CONFIG` are set to a missing path,
         // but not if `config.toml` hasn't been created.
         let mut toml = if !using_default_path || toml_path.exists() {
@@ -1534,6 +1537,7 @@ impl Config {
         let mut omit_git_hash = None;
         let mut lld_enabled = None;
 
+        let mut is_user_configured_rust_channel = false;
         if let Some(rust) = toml.rust {
             let Rust {
                 optimize: optimize_toml,
@@ -1591,6 +1595,7 @@ impl Config {
                 lld_mode,
             } = rust;
 
+            is_user_configured_rust_channel = channel.is_some();
             set(&mut config.channel, channel);
 
             config.download_rustc_commit = config.download_ci_rustc_commit(download_rustc);
@@ -1598,8 +1603,6 @@ impl Config {
             if config.download_rustc_commit.is_some() {
                 // We need the channel used by the downloaded compiler to match the one we set for rustdoc;
                 // otherwise rustdoc-ui tests break.
-                let ci_channel = t!(fs::read_to_string(config.src.join("src/ci/channel")));
-                let ci_channel = ci_channel.trim_end();
                 if config.channel != ci_channel
                     && !(config.channel == "dev" && ci_channel == "nightly")
                 {
@@ -1717,6 +1720,10 @@ impl Config {
         config.omit_git_hash = omit_git_hash.unwrap_or(default);
         config.rust_info = GitInfo::new(config.omit_git_hash, &config.src);
 
+        if config.rust_info.is_from_tarball() && !is_user_configured_rust_channel {
+            ci_channel.clone_into(&mut config.channel);
+        }
+
         if let Some(llvm) = toml.llvm {
             let Llvm {
                 optimize: optimize_toml,
diff --git a/tests/ui/associated-inherent-types/bugs/wf-check-skipped.next.stderr b/tests/ui/associated-inherent-types/bugs/wf-check-skipped.next.stderr
index 77fbaf52934..bf53089675d 100644
--- a/tests/ui/associated-inherent-types/bugs/wf-check-skipped.next.stderr
+++ b/tests/ui/associated-inherent-types/bugs/wf-check-skipped.next.stderr
@@ -1,8 +1,11 @@
-error: the type `Foo::Bar<Vec<[u32]>>` is not well-formed
-  --> $DIR/wf-check-skipped.rs:17:14
+error[E0277]: the size for values of type `[u32]` cannot be known at compilation time
+  --> $DIR/wf-check-skipped.rs:17:25
    |
 LL | fn main() -> Foo::Bar::<Vec<[u32]>> {}
-   |              ^^^^^^^^^^^^^^^^^^^^^^
+   |                         ^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u32]`
 
 error: aborting due to 1 previous error
 
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/associated-inherent-types/bugs/wf-check-skipped.rs b/tests/ui/associated-inherent-types/bugs/wf-check-skipped.rs
index 5b812a2295e..52df4efd13e 100644
--- a/tests/ui/associated-inherent-types/bugs/wf-check-skipped.rs
+++ b/tests/ui/associated-inherent-types/bugs/wf-check-skipped.rs
@@ -15,4 +15,4 @@ impl Foo {
 }
 
 fn main() -> Foo::Bar::<Vec<[u32]>> {}
-//[next]~^ ERROR the type `Foo::Bar<Vec<[u32]>>` is not well-formed
+//[next]~^ ERROR the size for values of type `[u32]` cannot be known at compilation time
diff --git a/tests/ui/feature-gates/feature-gate-stmt_expr_attributes.rs b/tests/ui/feature-gates/feature-gate-stmt_expr_attributes.rs
index f213e8933bf..85c08ec035e 100644
--- a/tests/ui/feature-gates/feature-gate-stmt_expr_attributes.rs
+++ b/tests/ui/feature-gates/feature-gate-stmt_expr_attributes.rs
@@ -1,4 +1,15 @@
 const X: i32 = #[allow(dead_code)] 8;
 //~^ ERROR attributes on expressions are experimental
 
+const Y: i32 =
+    /// foo
+//~^ ERROR attributes on expressions are experimental
+    8;
+
+const Z: i32 = {
+    //! foo
+//~^ ERROR attributes on expressions are experimental
+    8
+};
+
 fn main() {}
diff --git a/tests/ui/feature-gates/feature-gate-stmt_expr_attributes.stderr b/tests/ui/feature-gates/feature-gate-stmt_expr_attributes.stderr
index 67fdae030c0..14f7d58e47a 100644
--- a/tests/ui/feature-gates/feature-gate-stmt_expr_attributes.stderr
+++ b/tests/ui/feature-gates/feature-gate-stmt_expr_attributes.stderr
@@ -8,6 +8,28 @@ LL | const X: i32 = #[allow(dead_code)] 8;
    = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error: aborting due to 1 previous error
+error[E0658]: attributes on expressions are experimental
+  --> $DIR/feature-gate-stmt_expr_attributes.rs:5:5
+   |
+LL |     /// foo
+   |     ^^^^^^^
+   |
+   = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
+   = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = help: `///` is used for outer documentation comments; for a plain comment, use `//`
+
+error[E0658]: attributes on expressions are experimental
+  --> $DIR/feature-gate-stmt_expr_attributes.rs:10:5
+   |
+LL |     //! foo
+   |     ^^^^^^^
+   |
+   = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
+   = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = help: `//!` is used for inner documentation comments; for a plain comment, use `//` by removing the `!` or inserting a space in between them: `// !`
+
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/for/issue-20605.next.stderr b/tests/ui/for/issue-20605.next.stderr
index 6855e17df9a..98609211865 100644
--- a/tests/ui/for/issue-20605.next.stderr
+++ b/tests/ui/for/issue-20605.next.stderr
@@ -11,31 +11,13 @@ help: consider mutably borrowing here
 LL |     for item in &mut *things { *item = 0 }
    |                 ++++
 
-error: the type `<dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter` is not well-formed
-  --> $DIR/issue-20605.rs:6:17
-   |
-LL |     for item in *things { *item = 0 }
-   |                 ^^^^^^^
-
-error: the type `&mut <dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter` is not well-formed
-  --> $DIR/issue-20605.rs:6:17
-   |
-LL |     for item in *things { *item = 0 }
-   |                 ^^^^^^^
-
-error: the type `Option<<<dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter as Iterator>::Item>` is not well-formed
-  --> $DIR/issue-20605.rs:6:17
-   |
-LL |     for item in *things { *item = 0 }
-   |                 ^^^^^^^
-
 error[E0614]: type `<dyn Iterator<Item = &'a mut u8> as IntoIterator>::Item` cannot be dereferenced
   --> $DIR/issue-20605.rs:6:27
    |
 LL |     for item in *things { *item = 0 }
    |                           ^^^^^
 
-error: aborting due to 5 previous errors
+error: aborting due to 2 previous errors
 
 Some errors have detailed explanations: E0277, E0614.
 For more information about an error, try `rustc --explain E0277`.
diff --git a/tests/ui/for/issue-20605.rs b/tests/ui/for/issue-20605.rs
index b923a7088fe..647dc84028c 100644
--- a/tests/ui/for/issue-20605.rs
+++ b/tests/ui/for/issue-20605.rs
@@ -6,9 +6,6 @@ fn changer<'a>(mut things: Box<dyn Iterator<Item=&'a mut u8>>) {
     for item in *things { *item = 0 }
     //[current]~^ ERROR `dyn Iterator<Item = &'a mut u8>` is not an iterator
     //[next]~^^ ERROR `dyn Iterator<Item = &'a mut u8>` is not an iterator
-    //[next]~| ERROR the type `<dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter` is not well-formed
-    //[next]~| ERROR the type `&mut <dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter` is not well-formed
-    //[next]~| ERROR the type `Option<<<dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter as Iterator>::Item>` is not well-formed
     //[next]~| ERROR type `<dyn Iterator<Item = &'a mut u8> as IntoIterator>::Item` cannot be dereferenced
 
     // FIXME(-Znext-solver): these error messages are horrible and have to be
diff --git a/tests/ui/impl-trait/in-trait/alias-bounds-when-not-wf.rs b/tests/ui/impl-trait/in-trait/alias-bounds-when-not-wf.rs
index 365955166e6..5a6bf9bfaef 100644
--- a/tests/ui/impl-trait/in-trait/alias-bounds-when-not-wf.rs
+++ b/tests/ui/impl-trait/in-trait/alias-bounds-when-not-wf.rs
@@ -14,6 +14,6 @@ struct W<T>(T);
 // `usize: Foo` doesn't hold. Therefore we ICE, because we don't expect to still
 // encounter weak types in `assemble_alias_bound_candidates_recur`.
 fn hello(_: W<A<usize>>) {}
-//~^ ERROR the type `W<A<usize>>` is not well-formed
+//~^ ERROR the size for values of type `A<usize>` cannot be known at compilation time
 
 fn main() {}
diff --git a/tests/ui/impl-trait/in-trait/alias-bounds-when-not-wf.stderr b/tests/ui/impl-trait/in-trait/alias-bounds-when-not-wf.stderr
index 5df27ac3bc6..9663fab3d8c 100644
--- a/tests/ui/impl-trait/in-trait/alias-bounds-when-not-wf.stderr
+++ b/tests/ui/impl-trait/in-trait/alias-bounds-when-not-wf.stderr
@@ -7,11 +7,14 @@ LL | #![feature(lazy_type_alias)]
    = note: see issue #112792 <https://github.com/rust-lang/rust/issues/112792> for more information
    = note: `#[warn(incomplete_features)]` on by default
 
-error: the type `W<A<usize>>` is not well-formed
+error[E0277]: the size for values of type `A<usize>` cannot be known at compilation time
   --> $DIR/alias-bounds-when-not-wf.rs:16:13
    |
 LL | fn hello(_: W<A<usize>>) {}
-   |             ^^^^^^^^^^^
+   |             ^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `A<usize>`
 
 error: aborting due to 1 previous error; 1 warning emitted
 
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/lint/unused/unused-doc-comments-edge-cases.stderr b/tests/ui/lint/unused/unused-doc-comments-edge-cases.stderr
index add85b2f5e0..1ff5c8d8825 100644
--- a/tests/ui/lint/unused/unused-doc-comments-edge-cases.stderr
+++ b/tests/ui/lint/unused/unused-doc-comments-edge-cases.stderr
@@ -13,7 +13,7 @@ LL |     (/// useless doc comment
    = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
    = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-   = help: `///` is for documentation comments. For a plain comment, use `//`.
+   = help: `///` is used for outer documentation comments; for a plain comment, use `//`
 
 error: unused doc comment
   --> $DIR/unused-doc-comments-edge-cases.rs:6:9
diff --git a/tests/ui/traits/next-solver/canonical/const-region-infer-to-static-in-binder.stderr b/tests/ui/traits/next-solver/canonical/const-region-infer-to-static-in-binder.stderr
index 044c24fd2b2..170f2c7d34c 100644
--- a/tests/ui/traits/next-solver/canonical/const-region-infer-to-static-in-binder.stderr
+++ b/tests/ui/traits/next-solver/canonical/const-region-infer-to-static-in-binder.stderr
@@ -1,8 +1,8 @@
-error[E0282]: type annotations needed
+error[E0284]: type annotations needed: cannot satisfy `the constant `{ || {} }` can be evaluated`
   --> $DIR/const-region-infer-to-static-in-binder.rs:4:10
    |
 LL | struct X<const FN: fn() = { || {} }>;
-   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer the value of the constant `{ || {} }`
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot satisfy `the constant `{ || {} }` can be evaluated`
 
 error: using function pointers as const generic parameters is forbidden
   --> $DIR/const-region-infer-to-static-in-binder.rs:4:20
@@ -23,4 +23,4 @@ LL | struct X<const FN: fn() = { || {} }>;
 
 error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0282`.
+For more information about this error, try `rustc --explain E0284`.
diff --git a/tests/ui/traits/next-solver/issue-118950-root-region.rs b/tests/ui/traits/next-solver/issue-118950-root-region.rs
index 8667b3fe466..9f6dea5d5bf 100644
--- a/tests/ui/traits/next-solver/issue-118950-root-region.rs
+++ b/tests/ui/traits/next-solver/issue-118950-root-region.rs
@@ -12,7 +12,7 @@ trait ToUnit<'a> {
 trait Overlap<T> {}
 
 type Assoc<'a, T> = <*const T as ToUnit<'a>>::Unit;
-//~^ ERROR: not well-formed
+//~^ ERROR the trait bound `*const T: ToUnit<'a>` is not satisfied
 
 impl<T> Overlap<T> for T {}
 
diff --git a/tests/ui/traits/next-solver/issue-118950-root-region.stderr b/tests/ui/traits/next-solver/issue-118950-root-region.stderr
index 5cb24fa19aa..2e0566cad08 100644
--- a/tests/ui/traits/next-solver/issue-118950-root-region.stderr
+++ b/tests/ui/traits/next-solver/issue-118950-root-region.stderr
@@ -13,11 +13,17 @@ LL | #![feature(lazy_type_alias)]
    = note: see issue #112792 <https://github.com/rust-lang/rust/issues/112792> for more information
    = note: `#[warn(incomplete_features)]` on by default
 
-error: the type `<*const T as ToUnit<'a>>::Unit` is not well-formed
+error[E0277]: the trait bound `*const T: ToUnit<'a>` is not satisfied
   --> $DIR/issue-118950-root-region.rs:14:21
    |
 LL | type Assoc<'a, T> = <*const T as ToUnit<'a>>::Unit;
-   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `ToUnit<'a>` is not implemented for `*const T`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-118950-root-region.rs:8:1
+   |
+LL | trait ToUnit<'a> {
+   | ^^^^^^^^^^^^^^^^
 
 WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: ['^0.Named(DefId(0:15 ~ issue_118950_root_region[d54f]::{impl#1}::'a), "'a"), ?1t], def_id: DefId(0:8 ~ issue_118950_root_region[d54f]::Assoc) }
 WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: ['^0.Named(DefId(0:15 ~ issue_118950_root_region[d54f]::{impl#1}::'a), "'a"), ?1t], def_id: DefId(0:8 ~ issue_118950_root_region[d54f]::Assoc) }
@@ -34,5 +40,5 @@ LL | impl<T> Overlap<for<'a> fn(Assoc<'a, T>)> for T where Missing: Overlap<T> {
 
 error: aborting due to 3 previous errors; 1 warning emitted
 
-Some errors have detailed explanations: E0119, E0412.
+Some errors have detailed explanations: E0119, E0277, E0412.
 For more information about an error, try `rustc --explain E0119`.
diff --git a/tests/ui/traits/next-solver/member-constraints-in-root-universe.rs b/tests/ui/traits/next-solver/member-constraints-in-root-universe.rs
deleted file mode 100644
index a5696fc7796..00000000000
--- a/tests/ui/traits/next-solver/member-constraints-in-root-universe.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-//@ compile-flags: -Znext-solver
-
-trait Trait {
-    type Ty;
-}
-
-impl Trait for for<'a> fn(&'a u8, &'a u8) {
-    type Ty = ();
-}
-
-// argument is necessary to create universes before registering the hidden type.
-fn test<'a>(_: <fn(&u8, &u8) as Trait>::Ty) -> impl Sized {
-    //~^ ERROR the type `<for<'a, 'b> fn(&'a u8, &'b u8) as Trait>::Ty` is not well-formed
-    "hidden type is `&'?0 str` with '?0 member of ['static,]"
-}
-
-fn main() {}
diff --git a/tests/ui/traits/next-solver/member-constraints-in-root-universe.stderr b/tests/ui/traits/next-solver/member-constraints-in-root-universe.stderr
deleted file mode 100644
index 7a9982f07f6..00000000000
--- a/tests/ui/traits/next-solver/member-constraints-in-root-universe.stderr
+++ /dev/null
@@ -1,8 +0,0 @@
-error: the type `<for<'a, 'b> fn(&'a u8, &'b u8) as Trait>::Ty` is not well-formed
-  --> $DIR/member-constraints-in-root-universe.rs:12:16
-   |
-LL | fn test<'a>(_: <fn(&u8, &u8) as Trait>::Ty) -> impl Sized {
-   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 1 previous error
-
diff --git a/tests/ui/traits/next-solver/object-unsafety.rs b/tests/ui/traits/next-solver/object-unsafety.rs
index 3aa1af4956e..a347984daf6 100644
--- a/tests/ui/traits/next-solver/object-unsafety.rs
+++ b/tests/ui/traits/next-solver/object-unsafety.rs
@@ -10,9 +10,8 @@ fn copy<U: Setup + ?Sized>(from: &U::From) -> U::From {
 
 pub fn copy_any<T>(t: &T) -> T {
     copy::<dyn Setup<From=T>>(t)
-    //~^ ERROR the type `&<dyn Setup<From = T> as Setup>::From` is not well-formed
+    //~^ ERROR the trait bound `T: Copy` is not satisfied in `dyn Setup<From = T>`
     //~| ERROR mismatched types
-    //~| ERROR the type `<dyn Setup<From = T> as Setup>::From` is not well-formed
     //~| ERROR the trait bound `T: Copy` is not satisfied
 
     // FIXME(-Znext-solver): These error messages are horrible and some of them
diff --git a/tests/ui/traits/next-solver/object-unsafety.stderr b/tests/ui/traits/next-solver/object-unsafety.stderr
index 7c9a6077fe7..75d0ce24413 100644
--- a/tests/ui/traits/next-solver/object-unsafety.stderr
+++ b/tests/ui/traits/next-solver/object-unsafety.stderr
@@ -15,12 +15,6 @@ help: consider restricting type parameter `T`
 LL | pub fn copy_any<T: std::marker::Copy>(t: &T) -> T {
    |                  +++++++++++++++++++
 
-error: the type `&<dyn Setup<From = T> as Setup>::From` is not well-formed
-  --> $DIR/object-unsafety.rs:12:31
-   |
-LL |     copy::<dyn Setup<From=T>>(t)
-   |                               ^
-
 error[E0308]: mismatched types
   --> $DIR/object-unsafety.rs:12:31
    |
@@ -37,13 +31,19 @@ note: function defined here
 LL | fn copy<U: Setup + ?Sized>(from: &U::From) -> U::From {
    |    ^^^^                    --------------
 
-error: the type `<dyn Setup<From = T> as Setup>::From` is not well-formed
+error[E0277]: the trait bound `T: Copy` is not satisfied in `dyn Setup<From = T>`
   --> $DIR/object-unsafety.rs:12:5
    |
 LL |     copy::<dyn Setup<From=T>>(t)
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ within `dyn Setup<From = T>`, the trait `Copy` is not implemented for `T`, which is required by `dyn Setup<From = T>: Setup`
+   |
+   = note: required because it appears within the type `dyn Setup<From = T>`
+help: consider restricting type parameter `T`
+   |
+LL | pub fn copy_any<T: std::marker::Copy>(t: &T) -> T {
+   |                  +++++++++++++++++++
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
 Some errors have detailed explanations: E0277, E0308.
 For more information about an error, try `rustc --explain E0277`.
diff --git a/tests/ui/wf/wf-normalization-sized.next.stderr b/tests/ui/wf/wf-normalization-sized.next.stderr
index 599b1f3d45e..1e898fb7b78 100644
--- a/tests/ui/wf/wf-normalization-sized.next.stderr
+++ b/tests/ui/wf/wf-normalization-sized.next.stderr
@@ -1,30 +1,37 @@
-error: the type `<[[[[[[u8]]]]]] as WellUnformed>::RequestNormalize` is not well-formed
-  --> $DIR/wf-normalization-sized.rs:19:10
+error[E0277]: the size for values of type `[[[[[u8]]]]]` cannot be known at compilation time
+  --> $DIR/wf-normalization-sized.rs:19:11
    |
 LL | const _: <[[[[[[u8]]]]]] as WellUnformed>::RequestNormalize = ();
-   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |           ^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[[[[[u8]]]]]`
 
-error: the type `<[[[[[[u8]]]]]] as WellUnformed>::RequestNormalize` is not well-formed
-  --> $DIR/wf-normalization-sized.rs:19:10
+error[E0277]: the size for values of type `[[[[[u8]]]]]` cannot be known at compilation time
+  --> $DIR/wf-normalization-sized.rs:19:11
    |
 LL | const _: <[[[[[[u8]]]]]] as WellUnformed>::RequestNormalize = ();
-   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |           ^^^^^^^^^^^^^^ doesn't have a size known at compile-time
    |
+   = help: the trait `Sized` is not implemented for `[[[[[u8]]]]]`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: the type `<Vec<str> as WellUnformed>::RequestNormalize` is not well-formed
-  --> $DIR/wf-normalization-sized.rs:22:10
+error[E0277]: the size for values of type `str` cannot be known at compilation time
+  --> $DIR/wf-normalization-sized.rs:22:11
    |
 LL | const _: <Vec<str> as WellUnformed>::RequestNormalize = ();
-   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |           ^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `str`
 
-error: the type `<Vec<str> as WellUnformed>::RequestNormalize` is not well-formed
-  --> $DIR/wf-normalization-sized.rs:22:10
+error[E0277]: the size for values of type `str` cannot be known at compilation time
+  --> $DIR/wf-normalization-sized.rs:22:11
    |
 LL | const _: <Vec<str> as WellUnformed>::RequestNormalize = ();
-   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |           ^^^^^^^^ doesn't have a size known at compile-time
    |
+   = help: the trait `Sized` is not implemented for `str`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 4 previous errors
 
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/wf/wf-normalization-sized.rs b/tests/ui/wf/wf-normalization-sized.rs
index e6e24ff9e85..80b2c8803ff 100644
--- a/tests/ui/wf/wf-normalization-sized.rs
+++ b/tests/ui/wf/wf-normalization-sized.rs
@@ -17,10 +17,10 @@ impl<T: ?Sized> WellUnformed for T {
 }
 
 const _: <[[[[[[u8]]]]]] as WellUnformed>::RequestNormalize = ();
-//[next]~^ the type
-//[next]~| the type
+//[next]~^ the size for values of type `[[[[[u8]]]]]` cannot be known at compilation time
+//[next]~| the size for values of type `[[[[[u8]]]]]` cannot be known at compilation time
 const _: <Vec<str> as WellUnformed>::RequestNormalize = ();
-//[next]~^ the type
-//[next]~| the type
+//[next]~^ the size for values of type `str` cannot be known at compilation time
+//[next]~| the size for values of type `str` cannot be known at compilation time
 
 fn main() {}