Reword diagnostics about relaxed bounds in invalid contexts

19 files changed, 125 insertions, 240 deletions

diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index d3d521e83b0..533ee9bff54 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -60,7 +60,7 @@ use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_macros::extension;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
-use rustc_session::parse::{add_feature_diagnostics, feature_err};
+use rustc_session::parse::add_feature_diagnostics;
 use rustc_span::symbol::{Ident, Symbol, kw, sym};
 use rustc_span::{DUMMY_SP, DesugaringKind, Span};
 use smallvec::SmallVec;
@@ -2071,7 +2071,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         span: Span,
         rbp: RelaxedBoundPolicy<'_>,
     ) {
-        let err = |message| feature_err(&self.tcx.sess, sym::more_maybe_bounds, span, message);
+        // Even though feature `more_maybe_bounds` bypasses the given policy and (currently) enables
+        // relaxed bounds in every conceivable position[^1], we don't want to advertise it to the user
+        // (via a feature gate) since it's super internal. Besides this, it'd be quite distracting.
+        //
+        // [^1]: Strictly speaking, this is incorrect (at the very least for `Sized`) because it's
+        //       no longer fully consistent with default trait elaboration in HIR ty lowering.
 
         match rbp {
             RelaxedBoundPolicy::Allowed => return,
@@ -2093,11 +2098,17 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                 match reason {
                     RelaxedBoundForbiddenReason::TraitObjectTy => {
-                        err("`?Trait` is not permitted in trait object types").emit();
+                        self.dcx().span_err(
+                            span,
+                            "relaxed bounds are not permitted in trait object types",
+                        );
                         return;
                     }
                     RelaxedBoundForbiddenReason::SuperTrait => {
-                        let mut diag = err("`?Trait` is not permitted in supertraits");
+                        let mut diag = self.dcx().struct_span_err(
+                            span,
+                            "relaxed bounds are not permitted in supertrait bounds",
+                        );
                         if let Some(def_id) = trait_ref.trait_def_id()
                             && self.tcx.is_lang_item(def_id, hir::LangItem::Sized)
                         {
@@ -2111,7 +2122,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             }
         }
 
-        err("`?Trait` bounds are only permitted at the point where a type parameter is declared")
+        self.dcx()
+            .struct_span_err(span, "this relaxed bound is not permitted here")
+            .with_note(
+                "in this context, relaxed bounds are only allowed on \
+                 type parameters defined by the closest item",
+            )
             .emit();
     }
 
diff --git a/tests/ui/associated-item/missing-associated_item_or_field_def_ids.rs b/tests/ui/associated-item/missing-associated_item_or_field_def_ids.rs
index 18c71e5c744..029ce7d0e7e 100644
--- a/tests/ui/associated-item/missing-associated_item_or_field_def_ids.rs
+++ b/tests/ui/associated-item/missing-associated_item_or_field_def_ids.rs
@@ -2,6 +2,6 @@
 
 fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {
     //~^ ERROR expected trait, found associated function `Iterator::advance_by`
-    //~| ERROR `?Trait` is not permitted in trait object types
+    //~| ERROR relaxed bounds are not permitted in trait object types
     todo!()
 }
diff --git a/tests/ui/associated-item/missing-associated_item_or_field_def_ids.stderr b/tests/ui/associated-item/missing-associated_item_or_field_def_ids.stderr
index 6ec8e01c78d..ffe0b14a030 100644
--- a/tests/ui/associated-item/missing-associated_item_or_field_def_ids.stderr
+++ b/tests/ui/associated-item/missing-associated_item_or_field_def_ids.stderr
@@ -4,16 +4,12 @@ error[E0404]: expected trait, found associated function `Iterator::advance_by`
 LL | fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^ not a trait
 
-error[E0658]: `?Trait` is not permitted in trait object types
+error: relaxed bounds are not permitted in trait object types
   --> $DIR/missing-associated_item_or_field_def_ids.rs:3:29
    |
 LL | fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {
    |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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 2 previous errors
 
-Some errors have detailed explanations: E0404, E0658.
-For more information about an error, try `rustc --explain E0404`.
+For more information about this error, try `rustc --explain E0404`.
diff --git a/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.rs b/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.rs
index 9e0a86abb2e..bac4e608867 100644
--- a/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.rs
+++ b/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.rs
@@ -7,5 +7,5 @@ trait Tr {
 fn main() {
     let _: dyn Tr + ?Foo<Assoc = ()>;
     //~^ ERROR: cannot find trait `Foo` in this scope
-    //~| ERROR: `?Trait` is not permitted in trait object types
+    //~| ERROR: relaxed bounds are not permitted in trait object types
 }
diff --git a/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.stderr b/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.stderr
index bd83c1a9ea8..3660fcece62 100644
--- a/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.stderr
+++ b/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.stderr
@@ -4,16 +4,12 @@ error[E0405]: cannot find trait `Foo` in this scope
 LL |     let _: dyn Tr + ?Foo<Assoc = ()>;
    |                      ^^^ not found in this scope
 
-error[E0658]: `?Trait` is not permitted in trait object types
+error: relaxed bounds are not permitted in trait object types
   --> $DIR/avoid-getting-associated-items-of-undefined-trait.rs:8:21
    |
 LL |     let _: dyn Tr + ?Foo<Assoc = ()>;
    |                     ^^^^^^^^^^^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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 2 previous errors
 
-Some errors have detailed explanations: E0405, E0658.
-For more information about an error, try `rustc --explain E0405`.
+For more information about this error, try `rustc --explain E0405`.
diff --git a/tests/ui/feature-gates/feature-gate-more-maybe-bounds.rs b/tests/ui/feature-gates/feature-gate-more-maybe-bounds.rs
index 6a832744e3e..3066967f87e 100644
--- a/tests/ui/feature-gates/feature-gate-more-maybe-bounds.rs
+++ b/tests/ui/feature-gates/feature-gate-more-maybe-bounds.rs
@@ -2,13 +2,11 @@
 
 trait Trait1 {}
 auto trait Trait2 {}
-trait Trait3: ?Trait1 {}
-//~^  ERROR `?Trait` is not permitted in supertraits
-trait Trait4 where Self: ?Trait1 {}
-//~^ ERROR ?Trait` bounds are only permitted at the point where a type parameter is declared
+trait Trait3: ?Trait1 {} //~ ERROR relaxed bounds are not permitted in supertrait bounds
+trait Trait4 where Self: ?Trait1 {} //~ ERROR this relaxed bound is not permitted here
 
 fn foo(_: Box<dyn Trait1 + ?Trait2>) {}
-//~^  ERROR `?Trait` is not permitted in trait object types
+//~^  ERROR relaxed bounds are not permitted in trait object types
 fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
 //~^ ERROR type parameter has more than one relaxed default bound, only one is supported
 //~| ERROR relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
diff --git a/tests/ui/feature-gates/feature-gate-more-maybe-bounds.stderr b/tests/ui/feature-gates/feature-gate-more-maybe-bounds.stderr
index f52532a035b..35b5b80d69e 100644
--- a/tests/ui/feature-gates/feature-gate-more-maybe-bounds.stderr
+++ b/tests/ui/feature-gates/feature-gate-more-maybe-bounds.stderr
@@ -1,32 +1,25 @@
-error[E0658]: `?Trait` is not permitted in supertraits
+error: relaxed bounds are not permitted in supertrait bounds
   --> $DIR/feature-gate-more-maybe-bounds.rs:5:15
    |
 LL | trait Trait3: ?Trait1 {}
    |               ^^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared
-  --> $DIR/feature-gate-more-maybe-bounds.rs:7:26
+error: this relaxed bound is not permitted here
+  --> $DIR/feature-gate-more-maybe-bounds.rs:6:26
    |
 LL | trait Trait4 where Self: ?Trait1 {}
    |                          ^^^^^^^
    |
-   = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
 
-error[E0658]: `?Trait` is not permitted in trait object types
-  --> $DIR/feature-gate-more-maybe-bounds.rs:10:28
+error: relaxed bounds are not permitted in trait object types
+  --> $DIR/feature-gate-more-maybe-bounds.rs:8:28
    |
 LL | fn foo(_: Box<dyn Trait1 + ?Trait2>) {}
    |                            ^^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0203]: type parameter has more than one relaxed default bound, only one is supported
-  --> $DIR/feature-gate-more-maybe-bounds.rs:12:11
+  --> $DIR/feature-gate-more-maybe-bounds.rs:10:11
    |
 LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
    |           ^^^^^^^   ^^^^^^^
@@ -35,36 +28,35 @@ LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
-  --> $DIR/feature-gate-more-maybe-bounds.rs:12:11
+  --> $DIR/feature-gate-more-maybe-bounds.rs:10:11
    |
 LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
    |           ^^^^^^^
 
 error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
-  --> $DIR/feature-gate-more-maybe-bounds.rs:12:21
+  --> $DIR/feature-gate-more-maybe-bounds.rs:10:21
    |
 LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
    |                     ^^^^^^^
 
 error[E0203]: type parameter has more than one relaxed default bound, only one is supported
-  --> $DIR/feature-gate-more-maybe-bounds.rs:19:11
+  --> $DIR/feature-gate-more-maybe-bounds.rs:17:11
    |
 LL | fn baz<T: ?Trait + ?Trait>(_ : T) {}
    |           ^^^^^^   ^^^^^^
 
 error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
-  --> $DIR/feature-gate-more-maybe-bounds.rs:19:11
+  --> $DIR/feature-gate-more-maybe-bounds.rs:17:11
    |
 LL | fn baz<T: ?Trait + ?Trait>(_ : T) {}
    |           ^^^^^^
 
 error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
-  --> $DIR/feature-gate-more-maybe-bounds.rs:19:20
+  --> $DIR/feature-gate-more-maybe-bounds.rs:17:20
    |
 LL | fn baz<T: ?Trait + ?Trait>(_ : T) {}
    |                    ^^^^^^
 
 error: aborting due to 9 previous errors
 
-Some errors have detailed explanations: E0203, E0658.
-For more information about an error, try `rustc --explain E0203`.
+For more information about this error, try `rustc --explain E0203`.
diff --git a/tests/ui/parser/trait-object-trait-parens.rs b/tests/ui/parser/trait-object-trait-parens.rs
index 438034bc38a..51f0e2de611 100644
--- a/tests/ui/parser/trait-object-trait-parens.rs
+++ b/tests/ui/parser/trait-object-trait-parens.rs
@@ -6,17 +6,17 @@ fn f<T: (Copy) + (?Sized) + (for<'a> Trait<'a>)>() {}
 
 fn main() {
     let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>;
-    //~^ ERROR `?Trait` is not permitted in trait object types
+    //~^ ERROR relaxed bounds are not permitted in trait object types
     //~| ERROR only auto traits can be used as additional traits
     //~| WARN trait objects without an explicit `dyn` are deprecated
     //~| WARN this is accepted in the current edition
     let _: Box<?Sized + (for<'a> Trait<'a>) + (Obj)>;
-    //~^ ERROR `?Trait` is not permitted in trait object types
+    //~^ ERROR relaxed bounds are not permitted in trait object types
     //~| ERROR only auto traits can be used as additional traits
     //~| WARN trait objects without an explicit `dyn` are deprecated
     //~| WARN this is accepted in the current edition
     let _: Box<for<'a> Trait<'a> + (Obj) + (?Sized)>;
-    //~^ ERROR `?Trait` is not permitted in trait object types
+    //~^ ERROR relaxed bounds are not permitted in trait object types
     //~| ERROR only auto traits can be used as additional traits
     //~| WARN trait objects without an explicit `dyn` are deprecated
     //~| WARN this is accepted in the current edition
diff --git a/tests/ui/parser/trait-object-trait-parens.stderr b/tests/ui/parser/trait-object-trait-parens.stderr
index d75352b6811..26d388f8779 100644
--- a/tests/ui/parser/trait-object-trait-parens.stderr
+++ b/tests/ui/parser/trait-object-trait-parens.stderr
@@ -1,29 +1,20 @@
-error[E0658]: `?Trait` is not permitted in trait object types
+error: relaxed bounds are not permitted in trait object types
   --> $DIR/trait-object-trait-parens.rs:8:24
    |
 LL |     let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>;
    |                        ^^^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
+error: relaxed bounds are not permitted in trait object types
   --> $DIR/trait-object-trait-parens.rs:13:16
    |
 LL |     let _: Box<?Sized + (for<'a> Trait<'a>) + (Obj)>;
    |                ^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
+error: relaxed bounds are not permitted in trait object types
   --> $DIR/trait-object-trait-parens.rs:18:44
    |
 LL |     let _: Box<for<'a> Trait<'a> + (Obj) + (?Sized)>;
    |                                            ^^^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 warning: trait objects without an explicit `dyn` are deprecated
   --> $DIR/trait-object-trait-parens.rs:8:16
@@ -100,5 +91,4 @@ LL |     let _: Box<for<'a> Trait<'a> + (Obj) + (?Sized)>;
 
 error: aborting due to 6 previous errors; 3 warnings emitted
 
-Some errors have detailed explanations: E0225, E0658.
-For more information about an error, try `rustc --explain E0225`.
+For more information about this error, try `rustc --explain E0225`.
diff --git a/tests/ui/sized-hierarchy/default-supertrait.rs b/tests/ui/sized-hierarchy/default-supertrait.rs
index b25acf9e6ea..ab3b28e84db 100644
--- a/tests/ui/sized-hierarchy/default-supertrait.rs
+++ b/tests/ui/sized-hierarchy/default-supertrait.rs
@@ -6,18 +6,18 @@ use std::marker::{MetaSized, PointeeSized};
 trait Sized_: Sized { }
 
 trait NegSized: ?Sized { }
-//~^ ERROR `?Trait` is not permitted in supertraits
+//~^ ERROR relaxed bounds are not permitted in supertrait bounds
 
 trait MetaSized_: MetaSized { }
 
 trait NegMetaSized: ?MetaSized { }
-//~^ ERROR `?Trait` is not permitted in supertraits
+//~^ ERROR relaxed bounds are not permitted in supertrait bounds
 
 
 trait PointeeSized_: PointeeSized { }
 
 trait NegPointeeSized: ?PointeeSized { }
-//~^ ERROR `?Trait` is not permitted in supertraits
+//~^ ERROR relaxed bounds are not permitted in supertrait bounds
 
 trait Bare {}
 
diff --git a/tests/ui/sized-hierarchy/default-supertrait.stderr b/tests/ui/sized-hierarchy/default-supertrait.stderr
index 0cb4f346a63..f5589d6e279 100644
--- a/tests/ui/sized-hierarchy/default-supertrait.stderr
+++ b/tests/ui/sized-hierarchy/default-supertrait.stderr
@@ -1,30 +1,22 @@
-error[E0658]: `?Trait` is not permitted in supertraits
+error: relaxed bounds are not permitted in supertrait bounds
   --> $DIR/default-supertrait.rs:8:17
    |
 LL | trait NegSized: ?Sized { }
    |                 ^^^^^^
    |
-   = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
    = note: traits are `?Sized` by default
 
-error[E0658]: `?Trait` is not permitted in supertraits
+error: relaxed bounds are not permitted in supertrait bounds
   --> $DIR/default-supertrait.rs:13:21
    |
 LL | trait NegMetaSized: ?MetaSized { }
    |                     ^^^^^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in supertraits
+error: relaxed bounds are not permitted in supertrait bounds
   --> $DIR/default-supertrait.rs:19:24
    |
 LL | trait NegPointeeSized: ?PointeeSized { }
    |                        ^^^^^^^^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0277]: the size for values of type `T` cannot be known
   --> $DIR/default-supertrait.rs:52:38
@@ -119,5 +111,4 @@ LL | fn with_bare_trait<T: PointeeSized + Bare + std::marker::MetaSized>() {
 
 error: aborting due to 9 previous errors
 
-Some errors have detailed explanations: E0277, E0658.
-For more information about an error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/traits/maybe-trait-bounds-forbidden-locations.rs b/tests/ui/traits/maybe-trait-bounds-forbidden-locations.rs
deleted file mode 100644
index 04963c98765..00000000000
--- a/tests/ui/traits/maybe-trait-bounds-forbidden-locations.rs
+++ /dev/null
@@ -1,18 +0,0 @@
-//! Test that ?Trait bounds are forbidden in supertraits and trait object types.
-//!
-//! While `?Sized` and other maybe bounds are allowed in type parameter bounds and where clauses,
-//! they are explicitly forbidden in certain syntactic positions:
-//! - As supertraits in trait definitions
-//! - In trait object type expressions
-//!
-//! See https://github.com/rust-lang/rust/issues/20503
-
-trait Tr: ?Sized {}
-//~^ ERROR `?Trait` is not permitted in supertraits
-
-type A1 = dyn Tr + (?Sized);
-//~^ ERROR `?Trait` is not permitted in trait object types
-type A2 = dyn for<'a> Tr + (?Sized);
-//~^ ERROR `?Trait` is not permitted in trait object types
-
-fn main() {}
diff --git a/tests/ui/traits/maybe-trait-bounds-forbidden-locations.stderr b/tests/ui/traits/maybe-trait-bounds-forbidden-locations.stderr
deleted file mode 100644
index 5c4100d0e26..00000000000
--- a/tests/ui/traits/maybe-trait-bounds-forbidden-locations.stderr
+++ /dev/null
@@ -1,31 +0,0 @@
-error[E0658]: `?Trait` is not permitted in supertraits
-  --> $DIR/maybe-trait-bounds-forbidden-locations.rs:10:11
-   |
-LL | trait Tr: ?Sized {}
-   |           ^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-   = note: traits are `?Sized` by default
-
-error[E0658]: `?Trait` is not permitted in trait object types
-  --> $DIR/maybe-trait-bounds-forbidden-locations.rs:13:20
-   |
-LL | type A1 = dyn Tr + (?Sized);
-   |                    ^^^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
-  --> $DIR/maybe-trait-bounds-forbidden-locations.rs:15:28
-   |
-LL | type A2 = dyn for<'a> Tr + (?Sized);
-   |                            ^^^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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 3 previous errors
-
-For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/traits/wf-object/maybe-bound.rs b/tests/ui/traits/wf-object/maybe-bound.rs
deleted file mode 100644
index 17771e976ef..00000000000
--- a/tests/ui/traits/wf-object/maybe-bound.rs
+++ /dev/null
@@ -1,18 +0,0 @@
-// Test that `dyn ... + ?Sized + ...` is okay (though `?Sized` has no effect in trait objects).
-
-trait Foo {}
-
-type _0 = dyn ?Sized + Foo;
-//~^ ERROR `?Trait` is not permitted in trait object types
-
-type _1 = dyn Foo + ?Sized;
-//~^ ERROR `?Trait` is not permitted in trait object types
-
-type _2 = dyn Foo + ?Sized + ?Sized;
-//~^ ERROR `?Trait` is not permitted in trait object types
-//~| ERROR `?Trait` is not permitted in trait object types
-
-type _3 = dyn ?Sized + Foo;
-//~^ ERROR `?Trait` is not permitted in trait object types
-
-fn main() {}
diff --git a/tests/ui/traits/wf-object/maybe-bound.stderr b/tests/ui/traits/wf-object/maybe-bound.stderr
deleted file mode 100644
index be7afabd0d0..00000000000
--- a/tests/ui/traits/wf-object/maybe-bound.stderr
+++ /dev/null
@@ -1,48 +0,0 @@
-error[E0658]: `?Trait` is not permitted in trait object types
-  --> $DIR/maybe-bound.rs:5:15
-   |
-LL | type _0 = dyn ?Sized + Foo;
-   |               ^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
-  --> $DIR/maybe-bound.rs:8:21
-   |
-LL | type _1 = dyn Foo + ?Sized;
-   |                     ^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
-  --> $DIR/maybe-bound.rs:11:21
-   |
-LL | type _2 = dyn Foo + ?Sized + ?Sized;
-   |                     ^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
-  --> $DIR/maybe-bound.rs:11:30
-   |
-LL | type _2 = dyn Foo + ?Sized + ?Sized;
-   |                              ^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0658]: `?Trait` is not permitted in trait object types
-  --> $DIR/maybe-bound.rs:15:15
-   |
-LL | type _3 = dyn ?Sized + Foo;
-   |               ^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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 5 previous errors
-
-For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/traits/wf-object/only-maybe-bound.rs b/tests/ui/traits/wf-object/only-maybe-bound.rs
index 3e6db3e997c..96360e0331c 100644
--- a/tests/ui/traits/wf-object/only-maybe-bound.rs
+++ b/tests/ui/traits/wf-object/only-maybe-bound.rs
@@ -2,6 +2,6 @@
 
 type _0 = dyn ?Sized;
 //~^ ERROR at least one trait is required for an object type [E0224]
-//~| ERROR ?Trait` is not permitted in trait object types
+//~| ERROR relaxed bounds are not permitted in trait object types
 
 fn main() {}
diff --git a/tests/ui/traits/wf-object/only-maybe-bound.stderr b/tests/ui/traits/wf-object/only-maybe-bound.stderr
index 26269476eaa..6ae4568c699 100644
--- a/tests/ui/traits/wf-object/only-maybe-bound.stderr
+++ b/tests/ui/traits/wf-object/only-maybe-bound.stderr
@@ -1,11 +1,8 @@
-error[E0658]: `?Trait` is not permitted in trait object types
+error: relaxed bounds are not permitted in trait object types
   --> $DIR/only-maybe-bound.rs:3:15
    |
 LL | type _0 = dyn ?Sized;
    |               ^^^^^^
-   |
-   = help: add `#![feature(more_maybe_bounds)]` 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[E0224]: at least one trait is required for an object type
   --> $DIR/only-maybe-bound.rs:3:11
@@ -15,5 +12,4 @@ LL | type _0 = dyn ?Sized;
 
 error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0224, E0658.
-For more information about an error, try `rustc --explain E0224`.
+For more information about this error, try `rustc --explain E0224`.
diff --git a/tests/ui/unsized/relaxed-bounds-invalid-places.rs b/tests/ui/unsized/relaxed-bounds-invalid-places.rs
index ce3f35608be..e9f39d5f211 100644
--- a/tests/ui/unsized/relaxed-bounds-invalid-places.rs
+++ b/tests/ui/unsized/relaxed-bounds-invalid-places.rs
@@ -1,19 +1,18 @@
-// Test that relaxed bounds can only be placed on type parameters defined by the closest item
-// (ignoring relaxed bounds inside `impl Trait` and in associated type defs here).
+// Test various places where relaxed bounds are not permitted.
+//
+// Relaxed bounds are only permitted inside impl-Trait, assoc ty item bounds and
+// on type params defined by the closest item.
 
-struct S1<T>(T) where (T): ?Sized;
-//~^ ERROR `?Trait` bounds are only permitted at the point where a type parameter is declared
+struct S1<T>(T) where (T): ?Sized; //~ ERROR this relaxed bound is not permitted here
 
-struct S2<T>(T) where u8: ?Sized;
-//~^ ERROR `?Trait` bounds are only permitted at the point where a type parameter is declared
+struct S2<T>(T) where u8: ?Sized; //~ ERROR this relaxed bound is not permitted here
 
-struct S3<T>(T) where &'static T: ?Sized;
-//~^ ERROR `?Trait` bounds are only permitted at the point where a type parameter is declared
+struct S3<T>(T) where &'static T: ?Sized; //~ ERROR this relaxed bound is not permitted here
 
 trait Trait<'a> {}
 
 struct S4<T>(T) where for<'a> T: ?Trait<'a>;
-//~^ ERROR `?Trait` bounds are only permitted at the point where a type parameter is declared
+//~^ ERROR this relaxed bound is not permitted here
 //~| ERROR relaxing a default bound only does something for `?Sized`
 
 struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
@@ -21,11 +20,17 @@ struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
 //~| ERROR relaxing a default bound only does something for `?Sized`
 
 impl<T> S1<T> {
-    fn f() where T: ?Sized {}
-    //~^ ERROR `?Trait` bounds are only permitted at the point where a type parameter is declared
+    fn f() where T: ?Sized {} //~ ERROR this relaxed bound is not permitted here
 }
 
-fn main() {
-    let u = vec![1, 2, 3];
-    let _s: S5<[u8]> = S5(&u[..]); // OK
-}
+trait Tr: ?Sized {} //~ ERROR relaxed bounds are not permitted in supertrait bounds
+
+// Test that relaxed `Sized` bounds are rejected in trait object types:
+
+type O1 = dyn Tr + ?Sized; //~ ERROR relaxed bounds are not permitted in trait object types
+type O2 = dyn ?Sized + ?Sized + Tr;
+//~^ ERROR relaxed bounds are not permitted in trait object types
+//~| ERROR relaxed bounds are not permitted in trait object types
+
+fn main() {}
+
diff --git a/tests/ui/unsized/relaxed-bounds-invalid-places.stderr b/tests/ui/unsized/relaxed-bounds-invalid-places.stderr
index 3287eb8d1e9..a08dc15058a 100644
--- a/tests/ui/unsized/relaxed-bounds-invalid-places.stderr
+++ b/tests/ui/unsized/relaxed-bounds-invalid-places.stderr
@@ -1,56 +1,77 @@
-error[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared
-  --> $DIR/relaxed-bounds-invalid-places.rs:4:28
+error: this relaxed bound is not permitted here
+  --> $DIR/relaxed-bounds-invalid-places.rs:6:28
    |
 LL | struct S1<T>(T) where (T): ?Sized;
    |                            ^^^^^^
    |
-   = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
 
-error[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared
-  --> $DIR/relaxed-bounds-invalid-places.rs:7:27
+error: this relaxed bound is not permitted here
+  --> $DIR/relaxed-bounds-invalid-places.rs:8:27
    |
 LL | struct S2<T>(T) where u8: ?Sized;
    |                           ^^^^^^
    |
-   = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
 
-error[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared
+error: this relaxed bound is not permitted here
   --> $DIR/relaxed-bounds-invalid-places.rs:10:35
    |
 LL | struct S3<T>(T) where &'static T: ?Sized;
    |                                   ^^^^^^
    |
-   = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
 
-error[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared
-  --> $DIR/relaxed-bounds-invalid-places.rs:15:34
+error: this relaxed bound is not permitted here
+  --> $DIR/relaxed-bounds-invalid-places.rs:14:34
    |
 LL | struct S4<T>(T) where for<'a> T: ?Trait<'a>;
    |                                  ^^^^^^^^^^
    |
-   = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
 
-error[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared
-  --> $DIR/relaxed-bounds-invalid-places.rs:24:21
+error: this relaxed bound is not permitted here
+  --> $DIR/relaxed-bounds-invalid-places.rs:23:21
    |
 LL |     fn f() where T: ?Sized {}
    |                     ^^^^^^
    |
-   = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
+
+error: relaxed bounds are not permitted in supertrait bounds
+  --> $DIR/relaxed-bounds-invalid-places.rs:26:11
+   |
+LL | trait Tr: ?Sized {}
+   |           ^^^^^^
+   |
+   = note: traits are `?Sized` by default
+
+error: relaxed bounds are not permitted in trait object types
+  --> $DIR/relaxed-bounds-invalid-places.rs:30:20
+   |
+LL | type O1 = dyn Tr + ?Sized;
+   |                    ^^^^^^
+
+error: relaxed bounds are not permitted in trait object types
+  --> $DIR/relaxed-bounds-invalid-places.rs:31:15
+   |
+LL | type O2 = dyn ?Sized + ?Sized + Tr;
+   |               ^^^^^^
+
+error: relaxed bounds are not permitted in trait object types
+  --> $DIR/relaxed-bounds-invalid-places.rs:31:24
+   |
+LL | type O2 = dyn ?Sized + ?Sized + Tr;
+   |                        ^^^^^^
 
 error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
-  --> $DIR/relaxed-bounds-invalid-places.rs:15:34
+  --> $DIR/relaxed-bounds-invalid-places.rs:14:34
    |
 LL | struct S4<T>(T) where for<'a> T: ?Trait<'a>;
    |                                  ^^^^^^^^^^
 
 error[E0203]: type parameter has more than one relaxed default bound, only one is supported
-  --> $DIR/relaxed-bounds-invalid-places.rs:19:33
+  --> $DIR/relaxed-bounds-invalid-places.rs:18:33
    |
 LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
    |                                 ^^^^^^^^^^^^^^^   ^^^^^^
@@ -59,12 +80,11 @@ LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
-  --> $DIR/relaxed-bounds-invalid-places.rs:19:33
+  --> $DIR/relaxed-bounds-invalid-places.rs:18:33
    |
 LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
    |                                 ^^^^^^^^^^^^^^^
 
-error: aborting due to 8 previous errors
+error: aborting due to 12 previous errors
 
-Some errors have detailed explanations: E0203, E0658.
-For more information about an error, try `rustc --explain E0203`.
+For more information about this error, try `rustc --explain E0203`.