Refactor dyn-compatibility error and suggestions

This CL makes a number of small changes to dyn compatibility errors:
- "object safety" has been renamed to "dyn-compatibility" throughout
- "Convert to enum" suggestions are no longer generated when there
  exists a type-generic impl of the trait or an impl for `dyn OtherTrait`
- Several error messages are reorganized for user readability

Additionally, the dyn compatibility error creation code has been
split out into functions.

cc #132713
cc #133267

compiler/rustc_error_codes/src/error_codes/E0038.md

@@ -264,15 +264,15 @@ trait Foo {
 ### Trait contains associated constants
 
 Just like static functions, associated constants aren't stored on the method
-table. If the trait or any subtrait contain an associated constant, they cannot
-be made into an object.
+table. If the trait or any subtrait contain an associated constant, they are not
+dyn compatible.
 
 ```compile_fail,E0038
 trait Foo {
     const X: i32;
 }
 
-impl Foo {}
+impl dyn Foo {}
 ```
 
 A simple workaround is to use a helper method instead:

compiler/rustc_feature/src/removed.rs

@@ -163,7 +163,7 @@ macro_rules! declare_features {
     /// then removed. But there was no utility storing it separately, so now
     /// it's in this list.
     (removed, no_stack_check, "1.0.0", None, None),
-    /// Allows making `dyn Trait` well-formed even if `Trait` is not dyn-compatible (object safe).
+    /// Allows making `dyn Trait` well-formed even if `Trait` is not dyn compatible (object safe).
     /// Renamed to `dyn_compatible_for_dispatch`.
     (removed, object_safe_for_dispatch, "1.83.0", Some(43561),
      Some("renamed to `dyn_compatible_for_dispatch`")),

compiler/rustc_feature/src/unstable.rs

@@ -272,7 +272,7 @@ pub fn internal(&self, feature: Symbol) -> bool {
     (unstable, doc_notable_trait, "1.52.0", Some(45040)),
     /// Allows using the `may_dangle` attribute (RFC 1327).
     (unstable, dropck_eyepatch, "1.10.0", Some(34761)),
-    /// Allows making `dyn Trait` well-formed even if `Trait` is not dyn-compatible[^1].
+    /// Allows making `dyn Trait` well-formed even if `Trait` is not dyn compatible[^1].
     /// In that case, `dyn Trait: Trait` does not hold. Moreover, coercions and
     /// casts in safe Rust to `dyn Trait` for such a `Trait` is also forbidden.
     ///

compiler/rustc_hir_analysis/src/coherence/mod.rs

@@ -185,7 +185,7 @@ fn check_object_overlap<'tcx>(
     // check for overlap with the automatic `impl Trait for dyn Trait`
     if let ty::Dynamic(data, ..) = trait_ref.self_ty().kind() {
         // This is something like `impl Trait1 for Trait2`. Illegal if
-        // Trait1 is a supertrait of Trait2 or Trait2 is not dyn-compatible.
+        // Trait1 is a supertrait of Trait2 or Trait2 is not dyn compatible.
 
         let component_def_ids = data.iter().flat_map(|predicate| {
             match predicate.skip_binder() {

compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs

@@ -433,34 +433,19 @@ pub fn report_dyn_incompatibility<'tcx>(
         hir::Node::Item(item) => Some(item.ident.span),
         _ => None,
     });
+
     let mut err = struct_span_code_err!(
         tcx.dcx(),
         span,
         E0038,
-        "the {} `{}` cannot be made into an object",
+        "the {} `{}` is not dyn compatible",
         tcx.def_descr(trait_def_id),
         trait_str
     );
-    err.span_label(span, format!("`{trait_str}` cannot be made into an object"));
+    err.span_label(span, format!("`{trait_str}` is not dyn compatible"));
+
+    attempt_dyn_to_impl_suggestion(tcx, hir_id, &mut err);
 
-    if let Some(hir_id) = hir_id
-        && let hir::Node::Ty(ty) = tcx.hir_node(hir_id)
-        && let hir::TyKind::TraitObject([trait_ref, ..], ..) = ty.kind
-    {
-        let mut hir_id = hir_id;
-        while let hir::Node::Ty(ty) = tcx.parent_hir_node(hir_id) {
-            hir_id = ty.hir_id;
-        }
-        if tcx.parent_hir_node(hir_id).fn_sig().is_some() {
-            // Do not suggest `impl Trait` when dealing with things like super-traits.
-            err.span_suggestion_verbose(
-                ty.span.until(trait_ref.span),
-                "consider using an opaque type instead",
-                "impl ",
-                Applicability::MaybeIncorrect,
-            );
-        }
-    }
     let mut reported_violations = FxIndexSet::default();
     let mut multi_span = vec![];
     let mut messages = vec![];
@@ -475,7 +460,7 @@ pub fn report_dyn_incompatibility<'tcx>(
         if reported_violations.insert(violation.clone()) {
             let spans = violation.spans();
             let msg = if trait_span.is_none() || spans.is_empty() {
-                format!("the trait cannot be made into an object because {}", violation.error_msg())
+                format!("the trait is not dyn compatible because {}", violation.error_msg())
             } else {
                 format!("...because {}", violation.error_msg())
             };
@@ -492,7 +477,7 @@ pub fn report_dyn_incompatibility<'tcx>(
     let has_multi_span = !multi_span.is_empty();
     let mut note_span = MultiSpan::from_spans(multi_span.clone());
     if let (Some(trait_span), true) = (trait_span, has_multi_span) {
-        note_span.push_span_label(trait_span, "this trait cannot be made into an object...");
+        note_span.push_span_label(trait_span, "this trait is not dyn compatible...");
     }
     for (span, msg) in iter::zip(multi_span, messages) {
         note_span.push_span_label(span, msg);
@@ -500,16 +485,12 @@ pub fn report_dyn_incompatibility<'tcx>(
     // FIXME(dyn_compat_renaming): Update the URL.
     err.span_note(
         note_span,
-        "for a trait to be \"dyn-compatible\" it needs to allow building a vtable to allow the call \
-         to be resolvable dynamically; for more information visit \
-         <https://doc.rust-lang.org/reference/items/traits.html#object-safety>",
+        "for a trait to be dyn compatible it needs to allow building a vtable\n\
+        for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>",
     );
 
     // Only provide the help if its a local trait, otherwise it's not actionable.
     if trait_span.is_some() {
-        let mut reported_violations: Vec<_> = reported_violations.into_iter().collect();
-        reported_violations.sort();
-
         let mut potential_solutions: Vec<_> =
             reported_violations.into_iter().map(|violation| violation.solution()).collect();
         potential_solutions.sort();
@@ -520,68 +501,116 @@ pub fn report_dyn_incompatibility<'tcx>(
         }
     }
 
-    let impls_of = tcx.trait_impls_of(trait_def_id);
-    let impls = if impls_of.blanket_impls().is_empty() {
-        impls_of
-            .non_blanket_impls()
-            .values()
-            .flatten()
-            .filter(|def_id| {
-                !matches!(tcx.type_of(*def_id).instantiate_identity().kind(), ty::Dynamic(..))
-            })
-            .collect::<Vec<_>>()
-    } else {
-        vec![]
-    };
-    let externally_visible = if !impls.is_empty()
-        && let Some(def_id) = trait_def_id.as_local()
-        // We may be executing this during typeck, which would result in cycle
-        // if we used effective_visibilities query, which looks into opaque types
-        // (and therefore calls typeck).
-        && tcx.resolutions(()).effective_visibilities.is_exported(def_id)
-    {
-        true
-    } else {
-        false
-    };
-    match &impls[..] {
-        [] => {}
-        _ if impls.len() > 9 => {}
-        [only] if externally_visible => {
-            err.help(with_no_trimmed_paths!(format!(
-                "only type `{}` is seen to implement the trait in this crate, consider using it \
-                 directly instead",
-                tcx.type_of(*only).instantiate_identity(),
-            )));
-        }
-        [only] => {
-            err.help(with_no_trimmed_paths!(format!(
-                "only type `{}` implements the trait, consider using it directly instead",
-                tcx.type_of(*only).instantiate_identity(),
-            )));
-        }
-        impls => {
-            let types = impls
-                .iter()
-                .map(|t| {
-                    with_no_trimmed_paths!(format!("  {}", tcx.type_of(*t).instantiate_identity(),))
-                })
-                .collect::<Vec<_>>();
-            err.help(format!(
-                "the following types implement the trait, consider defining an enum where each \
-                 variant holds one of these types, implementing `{}` for this new enum and using \
-                 it instead:\n{}",
-                trait_str,
-                types.join("\n"),
-            ));
-        }
-    }
-    if externally_visible {
-        err.note(format!(
-            "`{trait_str}` can be implemented in other crates; if you want to support your users \
-             passing their own types here, you can't refer to a specific type",
-        ));
-    }
+    attempt_dyn_to_enum_suggestion(tcx, trait_def_id, &*trait_str, &mut err);
 
     err
 }
+
+/// Attempt to suggest converting the `dyn Trait` argument to an enumeration
+/// over the types that implement `Trait`.
+fn attempt_dyn_to_enum_suggestion(
+    tcx: TyCtxt<'_>,
+    trait_def_id: DefId,
+    trait_str: &str,
+    err: &mut Diag<'_>,
+) {
+    let impls_of = tcx.trait_impls_of(trait_def_id);
+
+    if !impls_of.blanket_impls().is_empty() {
+        return;
+    }
+
+    let concrete_impls: Option<Vec<Ty<'_>>> = impls_of
+        .non_blanket_impls()
+        .values()
+        .flatten()
+        .map(|impl_id| {
+            // Don't suggest conversion to enum if the impl types have type parameters.
+            // It's unlikely the user wants to define a generic enum.
+            let Some(impl_type) = tcx.type_of(*impl_id).no_bound_vars() else { return None };
+
+            // Obviously unsized impl types won't be usable in an enum.
+            // Note: this doesn't use `Ty::is_trivially_sized` because that function
+            // defaults to assuming that things are *not* sized, whereas we want to
+            // fall back to assuming that things may be sized.
+            match impl_type.kind() {
+                ty::Str | ty::Slice(_) | ty::Dynamic(_, _, ty::DynKind::Dyn) => {
+                    return None;
+                }
+                _ => {}
+            }
+            Some(impl_type)
+        })
+        .collect();
+    let Some(concrete_impls) = concrete_impls else { return };
+
+    const MAX_IMPLS_TO_SUGGEST_CONVERTING_TO_ENUM: usize = 9;
+    if concrete_impls.is_empty() || concrete_impls.len() > MAX_IMPLS_TO_SUGGEST_CONVERTING_TO_ENUM {
+        return;
+    }
+
+    let externally_visible = if let Some(def_id) = trait_def_id.as_local() {
+        // We may be executing this during typeck, which would result in cycle
+        // if we used effective_visibilities query, which looks into opaque types
+        // (and therefore calls typeck).
+        tcx.resolutions(()).effective_visibilities.is_exported(def_id)
+    } else {
+        false
+    };
+
+    if let [only_impl] = &concrete_impls[..] {
+        let within = if externally_visible { " within this crate" } else { "" };
+        err.help(with_no_trimmed_paths!(format!(
+            "only type `{only_impl}` implements `{trait_str}`{within}; \
+            consider using it directly instead."
+        )));
+    } else {
+        let types = concrete_impls
+            .iter()
+            .map(|t| with_no_trimmed_paths!(format!("  {}", t)))
+            .collect::<Vec<String>>()
+            .join("\n");
+
+        err.help(format!(
+            "the following types implement `{trait_str}`:\n\
+             {types}\n\
+             consider defining an enum where each variant holds one of these types,\n\
+             implementing `{trait_str}` for this new enum and using it instead",
+        ));
+    }
+
+    if externally_visible {
+        err.note(format!(
+            "`{trait_str}` may be implemented in other crates; if you want to support your users \
+             passing their own types here, you can't refer to a specific type",
+        ));
+    }
+}
+
+/// Attempt to suggest that a `dyn Trait` argument or return type be converted
+/// to use `impl Trait`.
+fn attempt_dyn_to_impl_suggestion(tcx: TyCtxt<'_>, hir_id: Option<hir::HirId>, err: &mut Diag<'_>) {
+    let Some(hir_id) = hir_id else { return };
+    let hir::Node::Ty(ty) = tcx.hir_node(hir_id) else { return };
+    let hir::TyKind::TraitObject([trait_ref, ..], ..) = ty.kind else { return };
+
+    // Only suggest converting `dyn` to `impl` if we're in a function signature.
+    // This ensures that we don't suggest converting e.g.
+    //   `type Alias = Box<dyn DynIncompatibleTrait>;` to
+    //   `type Alias = Box<impl DynIncompatibleTrait>;`
+    let Some((_id, first_non_type_parent_node)) =
+        tcx.hir().parent_iter(hir_id).find(|(_id, node)| !matches!(node, hir::Node::Ty(_)))
+    else {
+        return;
+    };
+    if first_non_type_parent_node.fn_sig().is_none() {
+        return;
+    }
+
+    err.span_suggestion_verbose(
+        ty.span.until(trait_ref.span),
+        "consider using an opaque type instead",
+        "impl ",
+        Applicability::MaybeIncorrect,
+    );
+}

compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs

@@ -53,7 +53,6 @@ fn dyn_compatibility_violations(
 ) -> &'_ [DynCompatibilityViolation] {
     debug_assert!(tcx.generics_of(trait_def_id).has_self);
     debug!("dyn_compatibility_violations: {:?}", trait_def_id);
-
     tcx.arena.alloc_from_iter(
         elaborate::supertrait_def_ids(tcx, trait_def_id)
             .flat_map(|def_id| dyn_compatibility_violations_for_trait(tcx, def_id)),

tests/rustdoc-ui/invalid_const_in_lifetime_position.rs

@@ -8,4 +8,4 @@ fn f<'a>(arg : Box<dyn X<Y<1> = &'a ()>>) {}
 //~| ERROR associated type takes 0 generic arguments but 1 generic argument
 //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
 //~| ERROR associated type takes 0 generic arguments but 1 generic argument
-//~| ERROR trait `X` cannot be made into an object
+//~| ERROR trait `X` is not dyn compatible

tests/rustdoc-ui/invalid_const_in_lifetime_position.stderr

@@ -92,17 +92,18 @@ LL |     type Y<'a>;
    |          ^
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error[E0038]: the trait `X` cannot be made into an object
+error[E0038]: the trait `X` is not dyn compatible
   --> $DIR/invalid_const_in_lifetime_position.rs:4:20
    |
 LL | fn f<'a>(arg : Box<dyn X<Y<1> = &'a ()>>) {}
-   |                    ^^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |                    ^^^^^^^^^^^^^^^^^^^^ `X` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/invalid_const_in_lifetime_position.rs:2:10
    |
 LL | trait X {
-   |       - this trait cannot be made into an object...
+   |       - this trait is not dyn compatible...
 LL |     type Y<'a>;
    |          ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait

tests/rustdoc-ui/issues/ice-generic-type-alias-105742.rs

@@ -5,8 +5,8 @@
 pub fn next<'a, T>(s: &'a mut dyn SVec<Item = T, Output = T>) {
     //~^ expected 1 lifetime argument
     //~| expected 1 generic argument
-    //~| the trait `SVec` cannot be made into an object
-    //~| `SVec` cannot be made into an object
+    //~| the trait `SVec` is not dyn compatible
+    //~| `SVec` is not dyn compatible
     //~| missing generics for associated type `SVec::Item`
     //~| missing generics for associated type `SVec::Item`
     let _ = s;

tests/rustdoc-ui/issues/ice-generic-type-alias-105742.stderr

@@ -294,19 +294,20 @@ help: add missing generic argument
 LL |     Output = <Self as SVec>::Item> as SVec>::Item<T>,
    |                                                  +++
 
-error[E0038]: the trait `SVec` cannot be made into an object
+error[E0038]: the trait `SVec` is not dyn compatible
   --> $DIR/ice-generic-type-alias-105742.rs:5:35
    |
 LL | pub fn next<'a, T>(s: &'a mut dyn SVec<Item = T, Output = T>) {
-   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^ `SVec` cannot be made into an object
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^ `SVec` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/ice-generic-type-alias-105742.rs:15:17
    |
 LL |    pub trait SVec: Index<
    |  ____________----__^
    | |            |
-   | |            this trait cannot be made into an object...
+   | |            this trait is not dyn compatible...
 LL | |      <Self as SVec>::Item,
 ...  |
 LL | |/     Output = <Index<<Self as SVec>::Item,

tests/ui/associated-consts/associated-const-in-trait.rs

@@ -5,9 +5,9 @@ trait Trait {
 }
 
 impl dyn Trait {
-    //~^ ERROR the trait `Trait` cannot be made into an object [E0038]
+    //~^ ERROR the trait `Trait` is not dyn compatible [E0038]
     const fn n() -> usize { Self::N }
-    //~^ ERROR the trait `Trait` cannot be made into an object [E0038]
+    //~^ ERROR the trait `Trait` is not dyn compatible [E0038]
 }
 
 fn main() {}

tests/ui/associated-consts/associated-const-in-trait.stderr

@@ -1,29 +1,31 @@
-error[E0038]: the trait `Trait` cannot be made into an object
+error[E0038]: the trait `Trait` is not dyn compatible
   --> $DIR/associated-const-in-trait.rs:7:6
    |
 LL | impl dyn Trait {
-   |      ^^^^^^^^^ `Trait` cannot be made into an object
+   |      ^^^^^^^^^ `Trait` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/associated-const-in-trait.rs:4:11
    |
 LL | trait Trait {
-   |       ----- this trait cannot be made into an object...
+   |       ----- this trait is not dyn compatible...
 LL |     const N: usize;
    |           ^ ...because it contains this associated `const`
    = help: consider moving `N` to another trait
 
-error[E0038]: the trait `Trait` cannot be made into an object
+error[E0038]: the trait `Trait` is not dyn compatible
   --> $DIR/associated-const-in-trait.rs:9:29
    |
 LL |     const fn n() -> usize { Self::N }
-   |                             ^^^^ `Trait` cannot be made into an object
+   |                             ^^^^ `Trait` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/associated-const-in-trait.rs:4:11
    |
 LL | trait Trait {
-   |       ----- this trait cannot be made into an object...
+   |       ----- this trait is not dyn compatible...
 LL |     const N: usize;
    |           ^ ...because it contains this associated `const`
    = help: consider moving `N` to another trait

tests/ui/associated-item/issue-48027.rs

@@ -3,6 +3,6 @@ trait Bar {
     fn return_n(&self) -> [u8; Bar::X]; //~ ERROR: E0790
 }
 
-impl dyn Bar {} //~ ERROR: the trait `Bar` cannot be made into an object
+impl dyn Bar {} //~ ERROR: the trait `Bar` is not dyn compatible
 
 fn main() {}

tests/ui/associated-item/issue-48027.stderr

@@ -1,14 +1,15 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/issue-48027.rs:6:6
    |
 LL | impl dyn Bar {}
-   |      ^^^^^^^ `Bar` cannot be made into an object
+   |      ^^^^^^^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-48027.rs:2:11
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     const X: usize;
    |           ^ ...because it contains this associated `const`
    = help: consider moving `X` to another trait

tests/ui/async-await/async-fn/dyn-pos.rs

@@ -1,6 +1,6 @@
 //@ edition:2018
 
 fn foo(x: &dyn AsyncFn()) {}
-//~^ ERROR the trait `AsyncFnMut` cannot be made into an object
+//~^ ERROR the trait `AsyncFnMut` is not dyn compatible
 
 fn main() {}

tests/ui/async-await/async-fn/dyn-pos.stderr

@@ -1,17 +1,14 @@
-error[E0038]: the trait `AsyncFnMut` cannot be made into an object
+error[E0038]: the trait `AsyncFnMut` is not dyn compatible
   --> $DIR/dyn-pos.rs:3:16
    |
 LL | fn foo(x: &dyn AsyncFn()) {}
-   |                ^^^^^^^^^ `AsyncFnMut` cannot be made into an object
+   |                ^^^^^^^^^ `AsyncFnMut` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
    |
-   = note: the trait cannot be made into an object because it contains the generic associated type `CallRefFuture`
-   = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `AsyncFnMut` for this new enum and using it instead:
-             &F
-             &mut F
-             std::boxed::Box<F, A>
+   = note: the trait is not dyn compatible because it contains the generic associated type `CallRefFuture`
 
 error: aborting due to 1 previous error
 

tests/ui/async-await/in-trait/dyn-compatibility.rs

@@ -7,5 +7,5 @@ trait Foo {
 
 fn main() {
     let x: &dyn Foo = todo!();
-    //~^ ERROR the trait `Foo` cannot be made into an object
+    //~^ ERROR the trait `Foo` is not dyn compatible
 }

tests/ui/async-await/in-trait/dyn-compatibility.stderr

@@ -1,14 +1,15 @@
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/dyn-compatibility.rs:9:12
    |
 LL |     let x: &dyn Foo = todo!();
-   |            ^^^^^^^^ `Foo` cannot be made into an object
+   |            ^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/dyn-compatibility.rs:5:14
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     async fn foo(&self);
    |              ^^^ ...because method `foo` is `async`
    = help: consider moving `foo` to another trait

tests/ui/async-await/inference_var_self_argument.rs

@@ -3,7 +3,7 @@
 
 trait Foo {
     async fn foo(self: &dyn Foo) {
-        //~^ ERROR: `Foo` cannot be made into an object
+        //~^ ERROR: `Foo` is not dyn compatible
         //~| ERROR invalid `self` parameter type: `&dyn Foo`
         todo!()
     }

tests/ui/async-await/inference_var_self_argument.stderr

@@ -7,17 +7,18 @@ LL |     async fn foo(self: &dyn Foo) {
    = note: type of `self` must be `Self` or a type that dereferences to it
    = help: consider changing to `self`, `&self`, `&mut self`, `self: Box<Self>`, `self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one of the previous types except `Self`)
 
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/inference_var_self_argument.rs:5:5
    |
 LL |     async fn foo(self: &dyn Foo) {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/inference_var_self_argument.rs:5:14
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     async fn foo(self: &dyn Foo) {
    |              ^^^ ...because method `foo` is `async`
    = help: consider moving `foo` to another trait

tests/ui/coherence/coherence-impl-trait-for-trait-dyn-compatible.stderr

@@ -1,16 +1,17 @@
-error[E0038]: the trait `DynIncompatible` cannot be made into an object
+error[E0038]: the trait `DynIncompatible` is not dyn compatible
   --> $DIR/coherence-impl-trait-for-trait-dyn-compatible.rs:7:26
    |
 LL | impl DynIncompatible for dyn DynIncompatible { }
-   |                          ^^^^^^^^^^^^^^^^^^^ `DynIncompatible` cannot be made into an object
+   |                          ^^^^^^^^^^^^^^^^^^^ `DynIncompatible` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/coherence-impl-trait-for-trait-dyn-compatible.rs:6:45
    |
 LL | trait DynIncompatible { fn eq(&self, other: Self); }
    |       ---------------                       ^^^^ ...because method `eq` references the `Self` type in this parameter
    |       |
-   |       this trait cannot be made into an object...
+   |       this trait is not dyn compatible...
    = help: consider moving `eq` to another trait
 
 error[E0046]: not all trait items implemented, missing: `eq`

tests/ui/const-generics/adt_const_params/const_param_ty_dyn_compatibility.stderr

@@ -1,28 +1,30 @@
-error[E0038]: the trait `ConstParamTy_` cannot be made into an object
+error[E0038]: the trait `ConstParamTy_` is not dyn compatible
   --> $DIR/const_param_ty_dyn_compatibility.rs:6:16
    |
 LL | fn foo(a: &dyn ConstParamTy_) {}
-   |                ^^^^^^^^^^^^^ `ConstParamTy_` cannot be made into an object
+   |                ^^^^^^^^^^^^^ `ConstParamTy_` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $SRC_DIR/core/src/cmp.rs:LL:COL
    |
-   = note: the trait cannot be made into an object because it uses `Self` as a type parameter
+   = note: the trait is not dyn compatible because it uses `Self` as a type parameter
 help: consider using an opaque type instead
    |
 LL | fn foo(a: &impl ConstParamTy_) {}
    |            ~~~~
 
-error[E0038]: the trait `UnsizedConstParamTy` cannot be made into an object
+error[E0038]: the trait `UnsizedConstParamTy` is not dyn compatible
   --> $DIR/const_param_ty_dyn_compatibility.rs:9:16
    |
 LL | fn bar(a: &dyn UnsizedConstParamTy) {}
-   |                ^^^^^^^^^^^^^^^^^^^ `UnsizedConstParamTy` cannot be made into an object
+   |                ^^^^^^^^^^^^^^^^^^^ `UnsizedConstParamTy` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $SRC_DIR/core/src/cmp.rs:LL:COL
    |
-   = note: the trait cannot be made into an object because it uses `Self` as a type parameter
+   = note: the trait is not dyn compatible because it uses `Self` as a type parameter
 help: consider using an opaque type instead
    |
 LL | fn bar(a: &impl UnsizedConstParamTy) {}

tests/ui/const-generics/generic_const_exprs/dyn-compatibility-err-ret.rs

@@ -14,8 +14,8 @@ impl Foo for () {
     }
 }
 
-fn use_dyn(v: &dyn Foo) { //~ERROR the trait `Foo` cannot be made into an object
-    v.test(); //~ERROR the trait `Foo` cannot be made into an object
+fn use_dyn(v: &dyn Foo) { //~ERROR the trait `Foo` is not dyn compatible
+    v.test(); //~ERROR the trait `Foo` is not dyn compatible
 }
 
 fn main() {}

tests/ui/const-generics/generic_const_exprs/dyn-compatibility-err-ret.stderr

@@ -1,38 +1,40 @@
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/dyn-compatibility-err-ret.rs:17:16
    |
 LL | fn use_dyn(v: &dyn Foo) {
-   |                ^^^^^^^ `Foo` cannot be made into an object
+   |                ^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/dyn-compatibility-err-ret.rs:8:8
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn test(&self) -> [u8; bar::<Self>()];
    |        ^^^^           ^^^^^^^^^^^^^^^^^^^ ...because method `test` references the `Self` type in its return type
    |        |
    |        ...because method `test` references the `Self` type in its `where` clause
    = help: consider moving `test` to another trait
-   = help: only type `()` implements the trait, consider using it directly instead
+   = help: only type `()` implements `Foo`; consider using it directly instead.
 
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/dyn-compatibility-err-ret.rs:18:5
    |
 LL |     v.test();
-   |     ^^^^^^^^ `Foo` cannot be made into an object
+   |     ^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/dyn-compatibility-err-ret.rs:8:8
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn test(&self) -> [u8; bar::<Self>()];
    |        ^^^^           ^^^^^^^^^^^^^^^^^^^ ...because method `test` references the `Self` type in its return type
    |        |
    |        ...because method `test` references the `Self` type in its `where` clause
    = help: consider moving `test` to another trait
-   = help: only type `()` implements the trait, consider using it directly instead
+   = help: only type `()` implements `Foo`; consider using it directly instead.
 
 error: aborting due to 2 previous errors
 

tests/ui/const-generics/generic_const_exprs/dyn-compatibility-err-where-bounds.rs

@@ -13,9 +13,9 @@ impl Foo for () {
 }
 
 fn use_dyn(v: &dyn Foo) {
-    //~^ ERROR the trait `Foo` cannot be made into an object
+    //~^ ERROR the trait `Foo` is not dyn compatible
     v.test();
-    //~^ ERROR the trait `Foo` cannot be made into an object
+    //~^ ERROR the trait `Foo` is not dyn compatible
 }
 
 fn main() {}

tests/ui/const-generics/generic_const_exprs/dyn-compatibility-err-where-bounds.stderr

@@ -1,34 +1,36 @@
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/dyn-compatibility-err-where-bounds.rs:15:16
    |
 LL | fn use_dyn(v: &dyn Foo) {
-   |                ^^^^^^^ `Foo` cannot be made into an object
+   |                ^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/dyn-compatibility-err-where-bounds.rs:8:8
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn test(&self) where [u8; bar::<Self>()]: Sized;
    |        ^^^^ ...because method `test` references the `Self` type in its `where` clause
    = help: consider moving `test` to another trait
-   = help: only type `()` implements the trait, consider using it directly instead
+   = help: only type `()` implements `Foo`; consider using it directly instead.
 
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/dyn-compatibility-err-where-bounds.rs:17:5
    |
 LL |     v.test();
-   |     ^^^^^^^^ `Foo` cannot be made into an object
+   |     ^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/dyn-compatibility-err-where-bounds.rs:8:8
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn test(&self) where [u8; bar::<Self>()]: Sized;
    |        ^^^^ ...because method `test` references the `Self` type in its `where` clause
    = help: consider moving `test` to another trait
-   = help: only type `()` implements the trait, consider using it directly instead
+   = help: only type `()` implements `Foo`; consider using it directly instead.
 
 error: aborting due to 2 previous errors
 

tests/ui/const-generics/generic_const_exprs/issue-102768.rs

@@ -13,7 +13,7 @@ fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
     //~| ERROR associated type takes 0 generic arguments but 1 generic argument
     //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
     //~| ERROR associated type takes 0 generic arguments but 1 generic argument
-    //~| ERROR `X` cannot be made into an object
+    //~| ERROR `X` is not dyn compatible
 };
 
 fn main() {}

tests/ui/const-generics/generic_const_exprs/issue-102768.stderr

@@ -92,17 +92,18 @@ LL |     type Y<'a>;
    |          ^
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error[E0038]: the trait `X` cannot be made into an object
+error[E0038]: the trait `X` is not dyn compatible
   --> $DIR/issue-102768.rs:9:24
    |
 LL |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
-   |                        ^^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |                        ^^^^^^^^^^^^^^^^^^^^ `X` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-102768.rs:5:10
    |
 LL | trait X {
-   |       - this trait cannot be made into an object...
+   |       - this trait is not dyn compatible...
 LL |     type Y<'a>;
    |          ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait

tests/ui/did_you_mean/trait-object-reference-without-parens-suggestion.rs

@@ -2,6 +2,6 @@
 
 fn main() {
     let _: &Copy + 'static; //~ ERROR expected a path
-    //~^ ERROR cannot be made into an object
+    //~^ ERROR is not dyn compatible
     let _: &'static Copy + 'static; //~ ERROR expected a path
 }

tests/ui/did_you_mean/trait-object-reference-without-parens-suggestion.stderr

@@ -20,14 +20,15 @@ help: try adding parentheses
 LL |     let _: &'static (Copy + 'static);
    |                     +              +
 
-error[E0038]: the trait `Copy` cannot be made into an object
+error[E0038]: the trait `Copy` is not dyn compatible
   --> $DIR/trait-object-reference-without-parens-suggestion.rs:4:12
    |
 LL |     let _: &Copy + 'static;
-   |            ^^^^^ `Copy` cannot be made into an object
+   |            ^^^^^ `Copy` is not dyn compatible
    |
-   = note: the trait cannot be made into an object because it requires `Self: Sized`
-   = note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+   = note: the trait is not dyn compatible because it requires `Self: Sized`
+   = note: for a trait to be dyn compatible it needs to allow building a vtable
+           for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
 
 error: aborting due to 3 previous errors
 

tests/ui/dyn-compatibility/almost-supertrait-associated-type.rs

@@ -5,8 +5,8 @@
 
 fn transmute<T, U>(t: T) -> U {
     (&PhantomData::<T> as &dyn Foo<T, U>).transmute(t)
-    //~^ ERROR the trait `Foo` cannot be made into an object
-    //~| ERROR the trait `Foo` cannot be made into an object
+    //~^ ERROR the trait `Foo` is not dyn compatible
+    //~| ERROR the trait `Foo` is not dyn compatible
 }
 
 struct ActuallySuper;
@@ -19,7 +19,7 @@ trait Dyn {
     type Out;
 }
 impl<T, U> Dyn for dyn Foo<T, U> + '_ {
-//~^ ERROR the trait `Foo` cannot be made into an object
+//~^ ERROR the trait `Foo` is not dyn compatible
     type Out = U;
 }
 impl<S: Dyn<Out = U> + ?Sized, U> Super<NotActuallySuper> for S {

tests/ui/dyn-compatibility/almost-supertrait-associated-type.stderr

@@ -1,53 +1,53 @@
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/almost-supertrait-associated-type.rs:21:20
    |
 LL | impl<T, U> Dyn for dyn Foo<T, U> + '_ {
-   |                    ^^^^^^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |                    ^^^^^^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/almost-supertrait-associated-type.rs:33:34
    |
 LL | trait Foo<T, U>: Super<ActuallySuper, Assoc = T>
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 ...
 LL |     fn transmute(&self, t: T) -> <Self as Super<NotActuallySuper>>::Assoc;
    |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...because method `transmute` references the `Self` type in its return type
    = help: consider moving `transmute` to another trait
-   = help: only type `std::marker::PhantomData<T>` implements the trait, consider using it directly instead
 
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/almost-supertrait-associated-type.rs:7:27
    |
 LL |     (&PhantomData::<T> as &dyn Foo<T, U>).transmute(t)
-   |                           ^^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |                           ^^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/almost-supertrait-associated-type.rs:33:34
    |
 LL | trait Foo<T, U>: Super<ActuallySuper, Assoc = T>
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 ...
 LL |     fn transmute(&self, t: T) -> <Self as Super<NotActuallySuper>>::Assoc;
    |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...because method `transmute` references the `Self` type in its return type
    = help: consider moving `transmute` to another trait
-   = help: only type `std::marker::PhantomData<T>` implements the trait, consider using it directly instead
 
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/almost-supertrait-associated-type.rs:7:6
    |
 LL |     (&PhantomData::<T> as &dyn Foo<T, U>).transmute(t)
-   |      ^^^^^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |      ^^^^^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/almost-supertrait-associated-type.rs:33:34
    |
 LL | trait Foo<T, U>: Super<ActuallySuper, Assoc = T>
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 ...
 LL |     fn transmute(&self, t: T) -> <Self as Super<NotActuallySuper>>::Assoc;
    |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...because method `transmute` references the `Self` type in its return type
    = help: consider moving `transmute` to another trait
-   = help: only type `std::marker::PhantomData<T>` implements the trait, consider using it directly instead
    = note: required for the cast from `&PhantomData<T>` to `&dyn Foo<T, U>`
 
 error: aborting due to 3 previous errors

tests/ui/dyn-compatibility/associated-consts.curr.stderr

@@ -1,29 +1,31 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/associated-consts.rs:12:31
    |
 LL | fn make_bar<T:Bar>(t: &T) -> &dyn Bar {
-   |                               ^^^^^^^ `Bar` cannot be made into an object
+   |                               ^^^^^^^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/associated-consts.rs:9:11
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     const X: usize;
    |           ^ ...because it contains this associated `const`
    = help: consider moving `X` to another trait
 
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/associated-consts.rs:14:5
    |
 LL |     t
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/associated-consts.rs:9:11
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     const X: usize;
    |           ^ ...because it contains this associated `const`
    = help: consider moving `X` to another trait

tests/ui/dyn-compatibility/associated-consts.dyn_compatible_for_dispatch.stderr

@@ -1,14 +1,15 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/associated-consts.rs:14:5
    |
 LL |     t
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/associated-consts.rs:9:11
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     const X: usize;
    |           ^ ...because it contains this associated `const`
    = help: consider moving `X` to another trait

tests/ui/dyn-compatibility/avoid-ice-on-warning-2.old.stderr

@@ -26,14 +26,15 @@ help: if this is a dyn-compatible trait, use `dyn`
 LL | fn id<F>(f: dyn Copy) -> usize {
    |             +++
 
-error[E0038]: the trait `Copy` cannot be made into an object
+error[E0038]: the trait `Copy` is not dyn compatible
   --> $DIR/avoid-ice-on-warning-2.rs:4:13
    |
 LL | fn id<F>(f: Copy) -> usize {
-   |             ^^^^ `Copy` cannot be made into an object
+   |             ^^^^ `Copy` is not dyn compatible
    |
-   = note: the trait cannot be made into an object because it requires `Self: Sized`
-   = note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+   = note: the trait is not dyn compatible because it requires `Self: Sized`
+   = note: for a trait to be dyn compatible it needs to allow building a vtable
+           for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
 
 error[E0618]: expected function, found `(dyn Copy + 'static)`
   --> $DIR/avoid-ice-on-warning-2.rs:12:5

tests/ui/dyn-compatibility/avoid-ice-on-warning-2.rs

@@ -3,7 +3,7 @@
 //@[new] edition:2021
 fn id<F>(f: Copy) -> usize {
 //[new]~^ ERROR expected a type, found a trait
-//[old]~^^ ERROR the trait `Copy` cannot be made into an object
+//[old]~^^ ERROR the trait `Copy` is not dyn compatible
 //[old]~| ERROR the size for values of type `(dyn Copy + 'static)`
 //[old]~| WARN trait objects without an explicit `dyn` are deprecated
 //[old]~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!

tests/ui/dyn-compatibility/avoid-ice-on-warning-3.old.stderr

@@ -65,19 +65,20 @@ help: if this is a dyn-compatible trait, use `dyn`
 LL | trait B { fn f(a: dyn A) -> A; }
    |                   +++
 
-error[E0038]: the trait `A` cannot be made into an object
+error[E0038]: the trait `A` is not dyn compatible
   --> $DIR/avoid-ice-on-warning-3.rs:4:19
    |
 LL | trait B { fn f(a: A) -> A; }
-   |                   ^ `A` cannot be made into an object
+   |                   ^ `A` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/avoid-ice-on-warning-3.rs:14:14
    |
 LL | trait A { fn g(b: B) -> B; }
    |       -      ^ ...because associated function `g` has no `self` parameter
    |       |
-   |       this trait cannot be made into an object...
+   |       this trait is not dyn compatible...
 help: consider turning `g` into a method by giving it a `&self` argument
    |
 LL | trait A { fn g(&self, b: B) -> B; }
@@ -101,19 +102,20 @@ help: if this is a dyn-compatible trait, use `dyn`
 LL | trait A { fn g(b: dyn B) -> B; }
    |                   +++
 
-error[E0038]: the trait `B` cannot be made into an object
+error[E0038]: the trait `B` is not dyn compatible
   --> $DIR/avoid-ice-on-warning-3.rs:14:19
    |
 LL | trait A { fn g(b: B) -> B; }
-   |                   ^ `B` cannot be made into an object
+   |                   ^ `B` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/avoid-ice-on-warning-3.rs:4:14
    |
 LL | trait B { fn f(a: A) -> A; }
    |       -      ^ ...because associated function `f` has no `self` parameter
    |       |
-   |       this trait cannot be made into an object...
+   |       this trait is not dyn compatible...
 help: consider turning `f` into a method by giving it a `&self` argument
    |
 LL | trait B { fn f(&self, a: A) -> A; }

tests/ui/dyn-compatibility/avoid-ice-on-warning-3.rs

@@ -4,7 +4,7 @@
 trait B { fn f(a: A) -> A; }
 //[new]~^ ERROR expected a type, found a trait
 //[new]~| ERROR expected a type, found a trait
-//[old]~^^^ ERROR the trait `A` cannot be made into an object
+//[old]~^^^ ERROR the trait `A` is not dyn compatible
 //[old]~| WARN trait objects without an explicit `dyn` are deprecated
 //[old]~| WARN trait objects without an explicit `dyn` are deprecated
 //[old]~| WARN trait objects without an explicit `dyn` are deprecated
@@ -14,7 +14,7 @@
 trait A { fn g(b: B) -> B; }
 //[new]~^ ERROR expected a type, found a trait
 //[new]~| ERROR expected a type, found a trait
-//[old]~^^^ ERROR the trait `B` cannot be made into an object
+//[old]~^^^ ERROR the trait `B` is not dyn compatible
 //[old]~| WARN trait objects without an explicit `dyn` are deprecated
 //[old]~| WARN trait objects without an explicit `dyn` are deprecated
 //[old]~| WARN trait objects without an explicit `dyn` are deprecated

tests/ui/dyn-compatibility/bare-trait-dont-suggest-dyn.new.fixed

@@ -5,7 +5,7 @@
 #![deny(bare_trait_objects)]
 fn ord_prefer_dot(s: String) -> impl Ord {
     //[new]~^ ERROR expected a type, found a trait
-    //[old]~^^ ERROR the trait `Ord` cannot be made into an object
+    //[old]~^^ ERROR the trait `Ord` is not dyn compatible
     //[old]~| ERROR trait objects without an explicit `dyn` are deprecated
     //[old]~| WARNING this is accepted in the current edition (Rust 2015)
     (s.starts_with("."), s)

tests/ui/dyn-compatibility/bare-trait-dont-suggest-dyn.old.stderr

@@ -16,19 +16,20 @@ help: if this is a dyn-compatible trait, use `dyn`
 LL | fn ord_prefer_dot(s: String) -> dyn Ord {
    |                                 +++
 
-error[E0038]: the trait `Ord` cannot be made into an object
+error[E0038]: the trait `Ord` is not dyn compatible
   --> $DIR/bare-trait-dont-suggest-dyn.rs:6:33
    |
 LL | fn ord_prefer_dot(s: String) -> Ord {
-   |                                 ^^^ `Ord` cannot be made into an object
+   |                                 ^^^ `Ord` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $SRC_DIR/core/src/cmp.rs:LL:COL
    |
-   = note: the trait cannot be made into an object because it uses `Self` as a type parameter
+   = note: the trait is not dyn compatible because it uses `Self` as a type parameter
   ::: $SRC_DIR/core/src/cmp.rs:LL:COL
    |
-   = note: the trait cannot be made into an object because it uses `Self` as a type parameter
+   = note: the trait is not dyn compatible because it uses `Self` as a type parameter
 help: consider using an opaque type instead
    |
 LL | fn ord_prefer_dot(s: String) -> impl Ord {

tests/ui/dyn-compatibility/bare-trait-dont-suggest-dyn.rs

@@ -5,7 +5,7 @@
 #![deny(bare_trait_objects)]
 fn ord_prefer_dot(s: String) -> Ord {
     //[new]~^ ERROR expected a type, found a trait
-    //[old]~^^ ERROR the trait `Ord` cannot be made into an object
+    //[old]~^^ ERROR the trait `Ord` is not dyn compatible
     //[old]~| ERROR trait objects without an explicit `dyn` are deprecated
     //[old]~| WARNING this is accepted in the current edition (Rust 2015)
     (s.starts_with("."), s)

tests/ui/dyn-compatibility/bounds.rs

@@ -5,7 +5,7 @@ trait X {
 }
 
 fn f() -> Box<dyn X<U = u32>> {
-    //~^ ERROR the trait `X` cannot be made into an object
+    //~^ ERROR the trait `X` is not dyn compatible
     loop {}
 }
 

tests/ui/dyn-compatibility/bounds.stderr

@@ -1,14 +1,15 @@
-error[E0038]: the trait `X` cannot be made into an object
+error[E0038]: the trait `X` is not dyn compatible
   --> $DIR/bounds.rs:7:15
    |
 LL | fn f() -> Box<dyn X<U = u32>> {
-   |               ^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |               ^^^^^^^^^^^^^^ `X` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/bounds.rs:4:13
    |
 LL | trait X {
-   |       - this trait cannot be made into an object...
+   |       - this trait is not dyn compatible...
 LL |     type U: PartialEq<Self>;
    |             ^^^^^^^^^^^^^^^ ...because it uses `Self` as a type parameter
 

tests/ui/dyn-compatibility/gat-incompatible-supertrait.rs

@@ -0,0 +1,18 @@
+// Test that the dyn-compatibility diagnostics for GATs refer first to the
+// user-named trait, not the GAT-containing supertrait.
+//
+// NOTE: this test is currently broken, and first reports:
+// "the trait `Super` is not dyn compatible"
+//
+//@ edition:2018
+
+trait Super {
+    type Assoc<'a>;
+}
+
+trait Child: Super {}
+
+fn take_dyn(_: &dyn Child) {}
+//~^ ERROR the trait `Super` is not dyn compatible
+
+fn main() {}

tests/ui/dyn-compatibility/gat-incompatible-supertrait.stderr

@@ -0,0 +1,19 @@
+error[E0038]: the trait `Super` is not dyn compatible
+  --> $DIR/gat-incompatible-supertrait.rs:15:21
+   |
+LL | fn take_dyn(_: &dyn Child) {}
+   |                     ^^^^^ `Super` is not dyn compatible
+   |
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/gat-incompatible-supertrait.rs:10:10
+   |
+LL | trait Super {
+   |       ----- this trait is not dyn compatible...
+LL |     type Assoc<'a>;
+   |          ^^^^^ ...because it contains the generic associated type `Assoc`
+   = help: consider moving `Assoc` to another trait
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0038`.

tests/ui/dyn-compatibility/generics.curr.stderr

@@ -1,75 +1,80 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/generics.rs:18:31
    |
 LL | fn make_bar<T:Bar>(t: &T) -> &dyn Bar {
-   |                               ^^^^^^^ `Bar` cannot be made into an object
+   |                               ^^^^^^^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/generics.rs:10:8
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar<T>(&self, t: T);
    |        ^^^ ...because method `bar` has generic type parameters
    = help: consider moving `bar` to another trait
 
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/generics.rs:25:40
    |
 LL | fn make_bar_explicit<T:Bar>(t: &T) -> &dyn Bar {
-   |                                        ^^^^^^^ `Bar` cannot be made into an object
+   |                                        ^^^^^^^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/generics.rs:10:8
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar<T>(&self, t: T);
    |        ^^^ ...because method `bar` has generic type parameters
    = help: consider moving `bar` to another trait
 
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/generics.rs:20:5
    |
 LL |     t
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/generics.rs:10:8
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar<T>(&self, t: T);
    |        ^^^ ...because method `bar` has generic type parameters
    = help: consider moving `bar` to another trait
    = note: required for the cast from `&T` to `&dyn Bar`
 
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/generics.rs:27:10
    |
 LL |     t as &dyn Bar
-   |          ^^^^^^^^ `Bar` cannot be made into an object
+   |          ^^^^^^^^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/generics.rs:10:8
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar<T>(&self, t: T);
    |        ^^^ ...because method `bar` has generic type parameters
    = help: consider moving `bar` to another trait
 
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/generics.rs:27:5
    |
 LL |     t as &dyn Bar
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/generics.rs:10:8
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar<T>(&self, t: T);
    |        ^^^ ...because method `bar` has generic type parameters
    = help: consider moving `bar` to another trait

tests/ui/dyn-compatibility/generics.dyn_compatible_for_dispatch.stderr

@@ -1,30 +1,32 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/generics.rs:20:5
    |
 LL |     t
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/generics.rs:10:8
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar<T>(&self, t: T);
    |        ^^^ ...because method `bar` has generic type parameters
    = help: consider moving `bar` to another trait
    = note: required for the cast from `&T` to `&dyn Bar`
 
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/generics.rs:27:5
    |
 LL |     t as &dyn Bar
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/generics.rs:10:8
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar<T>(&self, t: T);
    |        ^^^ ...because method `bar` has generic type parameters
    = help: consider moving `bar` to another trait

tests/ui/dyn-compatibility/mention-correct-dyn-incompatible-trait.stderr

@@ -1,36 +1,38 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/mention-correct-dyn-incompatible-trait.rs:19:15
    |
 LL |     let test: &mut dyn Bar = &mut thing;
-   |               ^^^^^^^^^^^^ `Bar` cannot be made into an object
+   |               ^^^^^^^^^^^^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/mention-correct-dyn-incompatible-trait.rs:4:8
    |
 LL |     fn foo<T>(&self, val: T);
    |        ^^^ ...because method `foo` has generic type parameters
 ...
 LL | trait Bar: Foo { }
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
    = help: consider moving `foo` to another trait
-   = help: only type `Thing` implements the trait, consider using it directly instead
+   = help: only type `Thing` implements `Bar`; consider using it directly instead.
 
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/mention-correct-dyn-incompatible-trait.rs:19:30
    |
 LL |     let test: &mut dyn Bar = &mut thing;
-   |                              ^^^^^^^^^^ `Bar` cannot be made into an object
+   |                              ^^^^^^^^^^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/mention-correct-dyn-incompatible-trait.rs:4:8
    |
 LL |     fn foo<T>(&self, val: T);
    |        ^^^ ...because method `foo` has generic type parameters
 ...
 LL | trait Bar: Foo { }
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
    = help: consider moving `foo` to another trait
-   = help: only type `Thing` implements the trait, consider using it directly instead
+   = help: only type `Thing` implements `Bar`; consider using it directly instead.
    = note: required for the cast from `&mut Thing` to `&mut dyn Bar`
 
 error: aborting due to 2 previous errors

tests/ui/dyn-compatibility/mentions-Self-in-super-predicates.rs

@@ -36,9 +36,9 @@ fn print_element_count(&self) {
 
 fn main() {
     let a: Box<dyn Expr> = Box::new(SExpr::new());
-    //~^ ERROR: `Expr` cannot be made into an object
+    //~^ ERROR: `Expr` is not dyn compatible
     let b: Box<dyn Expr> = Box::new(SExpr::new());
-    //~^ ERROR: `Expr` cannot be made into an object
+    //~^ ERROR: `Expr` is not dyn compatible
 
     // assert_eq!(a , b);
 }

tests/ui/dyn-compatibility/mentions-Self-in-super-predicates.stderr

@@ -1,47 +1,47 @@
-error[E0038]: the trait `Expr` cannot be made into an object
+error[E0038]: the trait `Expr` is not dyn compatible
   --> $DIR/mentions-Self-in-super-predicates.rs:12:27
    |
 LL |     elements: Vec<Box<dyn Expr + 'x>>,
-   |                           ^^^^ `Expr` cannot be made into an object
+   |                           ^^^^ `Expr` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/mentions-Self-in-super-predicates.rs:5:21
    |
 LL | trait Expr: Debug + PartialEq {
    |       ----          ^^^^^^^^^ ...because it uses `Self` as a type parameter
    |       |
-   |       this trait cannot be made into an object...
-   = help: only type `SExpr<'x>` implements the trait, consider using it directly instead
+   |       this trait is not dyn compatible...
 
-error[E0038]: the trait `Expr` cannot be made into an object
+error[E0038]: the trait `Expr` is not dyn compatible
   --> $DIR/mentions-Self-in-super-predicates.rs:38:20
    |
 LL |     let a: Box<dyn Expr> = Box::new(SExpr::new());
-   |                    ^^^^ `Expr` cannot be made into an object
+   |                    ^^^^ `Expr` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/mentions-Self-in-super-predicates.rs:5:21
    |
 LL | trait Expr: Debug + PartialEq {
    |       ----          ^^^^^^^^^ ...because it uses `Self` as a type parameter
    |       |
-   |       this trait cannot be made into an object...
-   = help: only type `SExpr<'x>` implements the trait, consider using it directly instead
+   |       this trait is not dyn compatible...
 
-error[E0038]: the trait `Expr` cannot be made into an object
+error[E0038]: the trait `Expr` is not dyn compatible
   --> $DIR/mentions-Self-in-super-predicates.rs:40:20
    |
 LL |     let b: Box<dyn Expr> = Box::new(SExpr::new());
-   |                    ^^^^ `Expr` cannot be made into an object
+   |                    ^^^^ `Expr` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/mentions-Self-in-super-predicates.rs:5:21
    |
 LL | trait Expr: Debug + PartialEq {
    |       ----          ^^^^^^^^^ ...because it uses `Self` as a type parameter
    |       |
-   |       this trait cannot be made into an object...
-   = help: only type `SExpr<'x>` implements the trait, consider using it directly instead
+   |       this trait is not dyn compatible...
 
 error: aborting due to 3 previous errors
 

tests/ui/dyn-compatibility/mentions-Self.curr.stderr

@@ -1,60 +1,64 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/mentions-Self.rs:22:31
    |
 LL | fn make_bar<T:Bar>(t: &T) -> &dyn Bar {
-   |                               ^^^^^^^ `Bar` cannot be made into an object
+   |                               ^^^^^^^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/mentions-Self.rs:11:22
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar(&self, x: &Self);
    |                      ^^^^^ ...because method `bar` references the `Self` type in this parameter
    = help: consider moving `bar` to another trait
 
-error[E0038]: the trait `Baz` cannot be made into an object
+error[E0038]: the trait `Baz` is not dyn compatible
   --> $DIR/mentions-Self.rs:28:31
    |
 LL | fn make_baz<T:Baz>(t: &T) -> &dyn Baz {
-   |                               ^^^^^^^ `Baz` cannot be made into an object
+   |                               ^^^^^^^ `Baz` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/mentions-Self.rs:15:22
    |
 LL | trait Baz {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn baz(&self) -> Self;
    |                      ^^^^ ...because method `baz` references the `Self` type in its return type
    = help: consider moving `baz` to another trait
 
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/mentions-Self.rs:24:5
    |
 LL |     t
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/mentions-Self.rs:11:22
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar(&self, x: &Self);
    |                      ^^^^^ ...because method `bar` references the `Self` type in this parameter
    = help: consider moving `bar` to another trait
    = note: required for the cast from `&T` to `&dyn Bar`
 
-error[E0038]: the trait `Baz` cannot be made into an object
+error[E0038]: the trait `Baz` is not dyn compatible
   --> $DIR/mentions-Self.rs:30:5
    |
 LL |     t
-   |     ^ `Baz` cannot be made into an object
+   |     ^ `Baz` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/mentions-Self.rs:15:22
    |
 LL | trait Baz {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn baz(&self) -> Self;
    |                      ^^^^ ...because method `baz` references the `Self` type in its return type
    = help: consider moving `baz` to another trait

tests/ui/dyn-compatibility/mentions-Self.dyn_compatible_for_dispatch.stderr

@@ -1,30 +1,32 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/mentions-Self.rs:24:5
    |
 LL |     t
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/mentions-Self.rs:11:22
    |
 LL | trait Bar {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar(&self, x: &Self);
    |                      ^^^^^ ...because method `bar` references the `Self` type in this parameter
    = help: consider moving `bar` to another trait
    = note: required for the cast from `&T` to `&dyn Bar`
 
-error[E0038]: the trait `Baz` cannot be made into an object
+error[E0038]: the trait `Baz` is not dyn compatible
   --> $DIR/mentions-Self.rs:30:5
    |
 LL |     t
-   |     ^ `Baz` cannot be made into an object
+   |     ^ `Baz` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/mentions-Self.rs:15:22
    |
 LL | trait Baz {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn baz(&self) -> Self;
    |                      ^^^^ ...because method `baz` references the `Self` type in its return type
    = help: consider moving `baz` to another trait

tests/ui/dyn-compatibility/missing-assoc-type.rs

@@ -2,6 +2,6 @@ trait Foo {
     type Bar<T>;
 }
 
-fn bar(x: &dyn Foo) {} //~ ERROR the trait `Foo` cannot be made into an object
+fn bar(x: &dyn Foo) {} //~ ERROR the trait `Foo` is not dyn compatible
 
 fn main() {}

tests/ui/dyn-compatibility/missing-assoc-type.stderr

@@ -1,14 +1,15 @@
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/missing-assoc-type.rs:5:16
    |
 LL | fn bar(x: &dyn Foo) {}
-   |                ^^^ `Foo` cannot be made into an object
+   |                ^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/missing-assoc-type.rs:2:10
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     type Bar<T>;
    |          ^^^ ...because it contains the generic associated type `Bar`
    = help: consider moving `Bar` to another trait

tests/ui/dyn-compatibility/no-static.curr.stderr

@@ -1,17 +1,18 @@
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/no-static.rs:12:22
    |
 LL | fn diverges() -> Box<dyn Foo> {
-   |                      ^^^^^^^ `Foo` cannot be made into an object
+   |                      ^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/no-static.rs:9:8
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn foo() {}
    |        ^^^ ...because associated function `foo` has no `self` parameter
-   = help: only type `Bar` implements the trait, consider using it directly instead
+   = help: only type `Bar` implements `Foo`; consider using it directly instead.
 help: consider turning `foo` into a method by giving it a `&self` argument
    |
 LL |     fn foo(&self) {}
@@ -21,20 +22,21 @@ help: alternatively, consider constraining `foo` so it does not apply to trait o
 LL |     fn foo() where Self: Sized {}
    |              +++++++++++++++++
 
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/no-static.rs:22:12
    |
 LL |     let b: Box<dyn Foo> = Box::new(Bar);
-   |            ^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |            ^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/no-static.rs:9:8
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn foo() {}
    |        ^^^ ...because associated function `foo` has no `self` parameter
-   = help: only type `Bar` implements the trait, consider using it directly instead
+   = help: only type `Bar` implements `Foo`; consider using it directly instead.
 help: consider turning `foo` into a method by giving it a `&self` argument
    |
 LL |     fn foo(&self) {}
@@ -44,20 +46,21 @@ help: alternatively, consider constraining `foo` so it does not apply to trait o
 LL |     fn foo() where Self: Sized {}
    |              +++++++++++++++++
 
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/no-static.rs:22:27
    |
 LL |     let b: Box<dyn Foo> = Box::new(Bar);
-   |                           ^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |                           ^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/no-static.rs:9:8
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn foo() {}
    |        ^^^ ...because associated function `foo` has no `self` parameter
-   = help: only type `Bar` implements the trait, consider using it directly instead
+   = help: only type `Bar` implements `Foo`; consider using it directly instead.
    = note: required for the cast from `Box<Bar>` to `Box<dyn Foo>`
 help: consider turning `foo` into a method by giving it a `&self` argument
    |

tests/ui/dyn-compatibility/no-static.dyn_compatible_for_dispatch.stderr

@@ -1,17 +1,18 @@
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/no-static.rs:22:27
    |
 LL |     let b: Box<dyn Foo> = Box::new(Bar);
-   |                           ^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |                           ^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/no-static.rs:9:8
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn foo() {}
    |        ^^^ ...because associated function `foo` has no `self` parameter
-   = help: only type `Bar` implements the trait, consider using it directly instead
+   = help: only type `Bar` implements `Foo`; consider using it directly instead.
    = note: required for the cast from `Box<Bar>` to `Box<dyn Foo>`
 help: consider turning `foo` into a method by giving it a `&self` argument
    |

tests/ui/dyn-compatibility/sized-2.curr.stderr

@@ -1,28 +1,30 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/sized-2.rs:14:31
    |
 LL | fn make_bar<T:Bar>(t: &T) -> &dyn Bar {
-   |                               ^^^^^^^ `Bar` cannot be made into an object
+   |                               ^^^^^^^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/sized-2.rs:9:18
    |
 LL | trait Bar
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     where Self : Sized
    |                  ^^^^^ ...because it requires `Self: Sized`
 
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/sized-2.rs:16:5
    |
 LL |     t
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/sized-2.rs:9:18
    |
 LL | trait Bar
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     where Self : Sized
    |                  ^^^^^ ...because it requires `Self: Sized`
    = note: required for the cast from `&T` to `&dyn Bar`

tests/ui/dyn-compatibility/sized-2.dyn_compatible_for_dispatch.stderr

@@ -1,14 +1,15 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/sized-2.rs:16:5
    |
 LL |     t
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/sized-2.rs:9:18
    |
 LL | trait Bar
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     where Self : Sized
    |                  ^^^^^ ...because it requires `Self: Sized`
    = note: required for the cast from `&T` to `&dyn Bar`

tests/ui/dyn-compatibility/sized.curr.stderr

@@ -1,30 +1,32 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/sized.rs:12:32
    |
 LL | fn make_bar<T: Bar>(t: &T) -> &dyn Bar {
-   |                                ^^^^^^^ `Bar` cannot be made into an object
+   |                                ^^^^^^^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/sized.rs:8:12
    |
 LL | trait Bar: Sized {
    |       ---  ^^^^^ ...because it requires `Self: Sized`
    |       |
-   |       this trait cannot be made into an object...
+   |       this trait is not dyn compatible...
 
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/sized.rs:14:5
    |
 LL |     t
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/sized.rs:8:12
    |
 LL | trait Bar: Sized {
    |       ---  ^^^^^ ...because it requires `Self: Sized`
    |       |
-   |       this trait cannot be made into an object...
+   |       this trait is not dyn compatible...
    = note: required for the cast from `&T` to `&dyn Bar`
 
 error: aborting due to 2 previous errors

tests/ui/dyn-compatibility/sized.dyn_compatible_for_dispatch.stderr

@@ -1,16 +1,17 @@
-error[E0038]: the trait `Bar` cannot be made into an object
+error[E0038]: the trait `Bar` is not dyn compatible
   --> $DIR/sized.rs:14:5
    |
 LL |     t
-   |     ^ `Bar` cannot be made into an object
+   |     ^ `Bar` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/sized.rs:8:12
    |
 LL | trait Bar: Sized {
    |       ---  ^^^^^ ...because it requires `Self: Sized`
    |       |
-   |       this trait cannot be made into an object...
+   |       this trait is not dyn compatible...
    = note: required for the cast from `&T` to `&dyn Bar`
 
 error: aborting due to 1 previous error

tests/ui/dyn-compatibility/supertrait-mentions-GAT.rs

@@ -9,7 +9,7 @@ trait GatTrait {
 trait SuperTrait<T>: for<'a> GatTrait<Gat<'a> = T> {
     fn c(&self) -> dyn SuperTrait<T>;
     //~^ ERROR associated item referring to unboxed trait object for its own trait
-    //~| ERROR the trait `SuperTrait` cannot be made into an object
+    //~| ERROR the trait `SuperTrait` is not dyn compatible
 }
 
 fn main() {}

tests/ui/dyn-compatibility/supertrait-mentions-GAT.stderr

@@ -20,20 +20,21 @@ help: you might have meant to use `Self` to refer to the implementing type
 LL |     fn c(&self) -> Self;
    |                    ~~~~
 
-error[E0038]: the trait `SuperTrait` cannot be made into an object
+error[E0038]: the trait `SuperTrait` is not dyn compatible
   --> $DIR/supertrait-mentions-GAT.rs:10:20
    |
 LL |     fn c(&self) -> dyn SuperTrait<T>;
-   |                    ^^^^^^^^^^^^^^^^^ `SuperTrait` cannot be made into an object
+   |                    ^^^^^^^^^^^^^^^^^ `SuperTrait` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/supertrait-mentions-GAT.rs:4:10
    |
 LL |     type Gat<'a>
    |          ^^^ ...because it contains the generic associated type `Gat`
 ...
 LL | trait SuperTrait<T>: for<'a> GatTrait<Gat<'a> = T> {
-   |       ---------- this trait cannot be made into an object...
+   |       ---------- this trait is not dyn compatible...
    = help: consider moving `Gat` to another trait
 
 error: aborting due to 3 previous errors

tests/ui/dyn-compatibility/supertrait-mentions-Self.stderr

@@ -18,19 +18,20 @@ help: consider relaxing the implicit `Sized` restriction
 LL | trait Bar<T: ?Sized> {
    |            ++++++++
 
-error[E0038]: the trait `Baz` cannot be made into an object
+error[E0038]: the trait `Baz` is not dyn compatible
   --> $DIR/supertrait-mentions-Self.rs:16:35
    |
 LL | fn make_baz<T:Baz>(t: &T) -> &dyn Baz {
-   |                                   ^^^ `Baz` cannot be made into an object
+   |                                   ^^^ `Baz` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/supertrait-mentions-Self.rs:8:13
    |
 LL | trait Baz : Bar<Self> {
    |       ---   ^^^^^^^^^ ...because it uses `Self` as a type parameter
    |       |
-   |       this trait cannot be made into an object...
+   |       this trait is not dyn compatible...
 help: consider using an opaque type instead
    |
 LL | fn make_baz<T:Baz>(t: &T) -> &impl Baz {

tests/ui/dyn-compatibility/taint-const-eval.curr.stderr

@@ -1,14 +1,15 @@
-error[E0038]: the trait `Qux` cannot be made into an object
+error[E0038]: the trait `Qux` is not dyn compatible
   --> $DIR/taint-const-eval.rs:11:15
    |
 LL | static FOO: &(dyn Qux + Sync) = "desc";
-   |               ^^^^^^^^^^^^^^ `Qux` cannot be made into an object
+   |               ^^^^^^^^^^^^^^ `Qux` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/taint-const-eval.rs:8:8
    |
 LL | trait Qux {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar();
    |        ^^^ ...because associated function `bar` has no `self` parameter
 help: consider turning `bar` into a method by giving it a `&self` argument
@@ -20,17 +21,18 @@ help: alternatively, consider constraining `bar` so it does not apply to trait o
 LL |     fn bar() where Self: Sized;
    |              +++++++++++++++++
 
-error[E0038]: the trait `Qux` cannot be made into an object
+error[E0038]: the trait `Qux` is not dyn compatible
   --> $DIR/taint-const-eval.rs:11:33
    |
 LL | static FOO: &(dyn Qux + Sync) = "desc";
-   |                                 ^^^^^^ `Qux` cannot be made into an object
+   |                                 ^^^^^^ `Qux` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/taint-const-eval.rs:8:8
    |
 LL | trait Qux {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar();
    |        ^^^ ...because associated function `bar` has no `self` parameter
    = note: required for the cast from `&'static str` to `&'static (dyn Qux + Sync + 'static)`
@@ -43,17 +45,18 @@ help: alternatively, consider constraining `bar` so it does not apply to trait o
 LL |     fn bar() where Self: Sized;
    |              +++++++++++++++++
 
-error[E0038]: the trait `Qux` cannot be made into an object
+error[E0038]: the trait `Qux` is not dyn compatible
   --> $DIR/taint-const-eval.rs:11:15
    |
 LL | static FOO: &(dyn Qux + Sync) = "desc";
-   |               ^^^^^^^^^^^^^^ `Qux` cannot be made into an object
+   |               ^^^^^^^^^^^^^^ `Qux` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/taint-const-eval.rs:8:8
    |
 LL | trait Qux {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar();
    |        ^^^ ...because associated function `bar` has no `self` parameter
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

tests/ui/dyn-compatibility/taint-const-eval.dyn_compatible_for_dispatch.stderr

@@ -1,14 +1,15 @@
-error[E0038]: the trait `Qux` cannot be made into an object
+error[E0038]: the trait `Qux` is not dyn compatible
   --> $DIR/taint-const-eval.rs:11:33
    |
 LL | static FOO: &(dyn Qux + Sync) = "desc";
-   |                                 ^^^^^^ `Qux` cannot be made into an object
+   |                                 ^^^^^^ `Qux` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/taint-const-eval.rs:8:8
    |
 LL | trait Qux {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     fn bar();
    |        ^^^ ...because associated function `bar` has no `self` parameter
    = note: required for the cast from `&'static str` to `&'static (dyn Qux + Sync + 'static)`

tests/ui/dyn-compatibility/taint-const-eval.rs

@@ -9,8 +9,8 @@ trait Qux {
 }
 
 static FOO: &(dyn Qux + Sync) = "desc";
-//~^ the trait `Qux` cannot be made into an object
-//[curr]~| the trait `Qux` cannot be made into an object
-//[curr]~| the trait `Qux` cannot be made into an object
+//~^ the trait `Qux` is not dyn compatible
+//[curr]~| the trait `Qux` is not dyn compatible
+//[curr]~| the trait `Qux` is not dyn compatible
 
 fn main() {}

tests/ui/dyn-compatibility/undispatchable-receiver-and-wc-references-Self.rs

@@ -17,13 +17,13 @@ fn get<'a>(self: &'a Box<Self>) -> Pin<Box<dyn Future<Output = Vec<u8>> + 'a>>
 }
 
 fn fetcher() -> Box<dyn Fetcher> {
-    //~^ ERROR the trait `Fetcher` cannot be made into an object
+    //~^ ERROR the trait `Fetcher` is not dyn compatible
     todo!()
 }
 
 pub fn foo() {
     let fetcher = fetcher();
-    //~^ ERROR the trait `Fetcher` cannot be made into an object
+    //~^ ERROR the trait `Fetcher` is not dyn compatible
     let _ = fetcher.get();
-    //~^ ERROR the trait `Fetcher` cannot be made into an object
+    //~^ ERROR the trait `Fetcher` is not dyn compatible
 }

tests/ui/dyn-compatibility/undispatchable-receiver-and-wc-references-Self.stderr

@@ -1,51 +1,54 @@
-error[E0038]: the trait `Fetcher` cannot be made into an object
+error[E0038]: the trait `Fetcher` is not dyn compatible
   --> $DIR/undispatchable-receiver-and-wc-references-Self.rs:19:21
    |
 LL |     fn get<'a>(self: &'a Box<Self>) -> Pin<Box<dyn Future<Output = Vec<u8>> + 'a>>
    |                      ------------- help: consider changing method `get`'s `self` parameter to be `&self`: `&Self`
 ...
 LL | fn fetcher() -> Box<dyn Fetcher> {
-   |                     ^^^^^^^^^^^ `Fetcher` cannot be made into an object
+   |                     ^^^^^^^^^^^ `Fetcher` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/undispatchable-receiver-and-wc-references-Self.rs:11:22
    |
 LL | pub trait Fetcher: Send + Sync {
-   |           ------- this trait cannot be made into an object...
+   |           ------- this trait is not dyn compatible...
 LL |     fn get<'a>(self: &'a Box<Self>) -> Pin<Box<dyn Future<Output = Vec<u8>> + 'a>>
    |                      ^^^^^^^^^^^^^ ...because method `get`'s `self` parameter cannot be dispatched on
 
-error[E0038]: the trait `Fetcher` cannot be made into an object
+error[E0038]: the trait `Fetcher` is not dyn compatible
   --> $DIR/undispatchable-receiver-and-wc-references-Self.rs:25:19
    |
 LL |     fn get<'a>(self: &'a Box<Self>) -> Pin<Box<dyn Future<Output = Vec<u8>> + 'a>>
    |                      ------------- help: consider changing method `get`'s `self` parameter to be `&self`: `&Self`
 ...
 LL |     let fetcher = fetcher();
-   |                   ^^^^^^^^^ `Fetcher` cannot be made into an object
+   |                   ^^^^^^^^^ `Fetcher` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/undispatchable-receiver-and-wc-references-Self.rs:11:22
    |
 LL | pub trait Fetcher: Send + Sync {
-   |           ------- this trait cannot be made into an object...
+   |           ------- this trait is not dyn compatible...
 LL |     fn get<'a>(self: &'a Box<Self>) -> Pin<Box<dyn Future<Output = Vec<u8>> + 'a>>
    |                      ^^^^^^^^^^^^^ ...because method `get`'s `self` parameter cannot be dispatched on
 
-error[E0038]: the trait `Fetcher` cannot be made into an object
+error[E0038]: the trait `Fetcher` is not dyn compatible
   --> $DIR/undispatchable-receiver-and-wc-references-Self.rs:27:13
    |
 LL |     fn get<'a>(self: &'a Box<Self>) -> Pin<Box<dyn Future<Output = Vec<u8>> + 'a>>
    |                      ------------- help: consider changing method `get`'s `self` parameter to be `&self`: `&Self`
 ...
 LL |     let _ = fetcher.get();
-   |             ^^^^^^^^^^^^^ `Fetcher` cannot be made into an object
+   |             ^^^^^^^^^^^^^ `Fetcher` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/undispatchable-receiver-and-wc-references-Self.rs:11:22
    |
 LL | pub trait Fetcher: Send + Sync {
-   |           ------- this trait cannot be made into an object...
+   |           ------- this trait is not dyn compatible...
 LL |     fn get<'a>(self: &'a Box<Self>) -> Pin<Box<dyn Future<Output = Vec<u8>> + 'a>>
    |                      ^^^^^^^^^^^^^ ...because method `get`'s `self` parameter cannot be dispatched on
 

tests/ui/error-codes/E0038.stderr

@@ -1,29 +1,31 @@
-error[E0038]: the trait `Trait` cannot be made into an object
+error[E0038]: the trait `Trait` is not dyn compatible
   --> $DIR/E0038.rs:5:20
    |
 LL | fn call_foo(x: Box<dyn Trait>) {
-   |                    ^^^^^^^^^ `Trait` cannot be made into an object
+   |                    ^^^^^^^^^ `Trait` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/E0038.rs:2:22
    |
 LL | trait Trait {
-   |       ----- this trait cannot be made into an object...
+   |       ----- this trait is not dyn compatible...
 LL |     fn foo(&self) -> Self;
    |                      ^^^^ ...because method `foo` references the `Self` type in its return type
    = help: consider moving `foo` to another trait
 
-error[E0038]: the trait `Trait` cannot be made into an object
+error[E0038]: the trait `Trait` is not dyn compatible
   --> $DIR/E0038.rs:7:13
    |
 LL |     let y = x.foo();
-   |             ^^^^^^^ `Trait` cannot be made into an object
+   |             ^^^^^^^ `Trait` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/E0038.rs:2:22
    |
 LL | trait Trait {
-   |       ----- this trait cannot be made into an object...
+   |       ----- this trait is not dyn compatible...
 LL |     fn foo(&self) -> Self;
    |                      ^^^^ ...because method `foo` references the `Self` type in its return type
    = help: consider moving `foo` to another trait

tests/ui/feature-gates/feature-gate-async-fn-in-dyn-trait.rs

@@ -5,10 +5,10 @@ trait Foo {
 }
 
 async fn takes_dyn_trait(x: &dyn Foo) {
-    //~^ ERROR the trait `Foo` cannot be made into an object
+    //~^ ERROR the trait `Foo` is not dyn compatible
     x.bar().await;
-    //~^ ERROR the trait `Foo` cannot be made into an object
-    //~| ERROR the trait `Foo` cannot be made into an object
+    //~^ ERROR the trait `Foo` is not dyn compatible
+    //~| ERROR the trait `Foo` is not dyn compatible
 }
 
 fn main() {}

tests/ui/feature-gates/feature-gate-async-fn-in-dyn-trait.stderr

@@ -1,44 +1,47 @@
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/feature-gate-async-fn-in-dyn-trait.rs:7:30
    |
 LL | async fn takes_dyn_trait(x: &dyn Foo) {
-   |                              ^^^^^^^ `Foo` cannot be made into an object
+   |                              ^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/feature-gate-async-fn-in-dyn-trait.rs:4:14
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     async fn bar(&self);
    |              ^^^ ...because method `bar` is `async`
    = help: consider moving `bar` to another trait
 
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/feature-gate-async-fn-in-dyn-trait.rs:9:7
    |
 LL |     x.bar().await;
-   |       ^^^ `Foo` cannot be made into an object
+   |       ^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/feature-gate-async-fn-in-dyn-trait.rs:4:14
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     async fn bar(&self);
    |              ^^^ ...because method `bar` is `async`
    = help: consider moving `bar` to another trait
 
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/feature-gate-async-fn-in-dyn-trait.rs:9:5
    |
 LL |     x.bar().await;
-   |     ^^^^^^^ `Foo` cannot be made into an object
+   |     ^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/feature-gate-async-fn-in-dyn-trait.rs:4:14
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     async fn bar(&self);
    |              ^^^ ...because method `bar` is `async`
    = help: consider moving `bar` to another trait

tests/ui/feature-gates/feature-gate-dispatch-from-dyn-missing-impl.rs

@@ -30,6 +30,6 @@ fn ptr(self: Ptr<Self>) {}
 
 fn main() {
     Ptr(Box::new(4)) as Ptr<dyn Trait>;
-    //~^ ERROR the trait `Trait` cannot be made into an object
-    //~^^ ERROR the trait `Trait` cannot be made into an object
+    //~^ ERROR the trait `Trait` is not dyn compatible
+    //~^^ ERROR the trait `Trait` is not dyn compatible
 }

tests/ui/feature-gates/feature-gate-dispatch-from-dyn-missing-impl.stderr

@@ -1,38 +1,40 @@
-error[E0038]: the trait `Trait` cannot be made into an object
+error[E0038]: the trait `Trait` is not dyn compatible
   --> $DIR/feature-gate-dispatch-from-dyn-missing-impl.rs:32:25
    |
 LL |     fn ptr(self: Ptr<Self>);
    |                  --------- help: consider changing method `ptr`'s `self` parameter to be `&self`: `&Self`
 ...
 LL |     Ptr(Box::new(4)) as Ptr<dyn Trait>;
-   |                         ^^^^^^^^^^^^^^ `Trait` cannot be made into an object
+   |                         ^^^^^^^^^^^^^^ `Trait` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/feature-gate-dispatch-from-dyn-missing-impl.rs:25:18
    |
 LL | trait Trait {
-   |       ----- this trait cannot be made into an object...
+   |       ----- this trait is not dyn compatible...
 LL |     fn ptr(self: Ptr<Self>);
    |                  ^^^^^^^^^ ...because method `ptr`'s `self` parameter cannot be dispatched on
-   = help: only type `i32` implements the trait, consider using it directly instead
+   = help: only type `i32` implements `Trait`; consider using it directly instead.
 
-error[E0038]: the trait `Trait` cannot be made into an object
+error[E0038]: the trait `Trait` is not dyn compatible
   --> $DIR/feature-gate-dispatch-from-dyn-missing-impl.rs:32:5
    |
 LL |     fn ptr(self: Ptr<Self>);
    |                  --------- help: consider changing method `ptr`'s `self` parameter to be `&self`: `&Self`
 ...
 LL |     Ptr(Box::new(4)) as Ptr<dyn Trait>;
-   |     ^^^^^^^^^^^^^^^^ `Trait` cannot be made into an object
+   |     ^^^^^^^^^^^^^^^^ `Trait` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/feature-gate-dispatch-from-dyn-missing-impl.rs:25:18
    |
 LL | trait Trait {
-   |       ----- this trait cannot be made into an object...
+   |       ----- this trait is not dyn compatible...
 LL |     fn ptr(self: Ptr<Self>);
    |                  ^^^^^^^^^ ...because method `ptr`'s `self` parameter cannot be dispatched on
-   = help: only type `i32` implements the trait, consider using it directly instead
+   = help: only type `i32` implements `Trait`; consider using it directly instead.
    = note: required for the cast from `Ptr<{integer}>` to `Ptr<dyn Trait>`
 
 error: aborting due to 2 previous errors

tests/ui/feature-gates/feature-gate-dyn_compatible_for_dispatch.stderr

@@ -1,28 +1,30 @@
-error[E0038]: the trait `DynIncompatible1` cannot be made into an object
+error[E0038]: the trait `DynIncompatible1` is not dyn compatible
   --> $DIR/feature-gate-dyn_compatible_for_dispatch.rs:18:40
    |
 LL | fn takes_dyn_incompatible_ref<T>(obj: &dyn DynIncompatible1) {
-   |                                        ^^^^^^^^^^^^^^^^^^^^ `DynIncompatible1` cannot be made into an object
+   |                                        ^^^^^^^^^^^^^^^^^^^^ `DynIncompatible1` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/feature-gate-dyn_compatible_for_dispatch.rs:4:25
    |
 LL | trait DynIncompatible1: Sized {}
    |       ----------------  ^^^^^ ...because it requires `Self: Sized`
    |       |
-   |       this trait cannot be made into an object...
+   |       this trait is not dyn compatible...
 
-error[E0038]: the trait `DynIncompatible2` cannot be made into an object
+error[E0038]: the trait `DynIncompatible2` is not dyn compatible
   --> $DIR/feature-gate-dyn_compatible_for_dispatch.rs:22:46
    |
 LL | fn return_dyn_incompatible_ref() -> &'static dyn DynIncompatible2 {
-   |                                              ^^^^^^^^^^^^^^^^^^^^ `DynIncompatible2` cannot be made into an object
+   |                                              ^^^^^^^^^^^^^^^^^^^^ `DynIncompatible2` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/feature-gate-dyn_compatible_for_dispatch.rs:7:8
    |
 LL | trait DynIncompatible2 {
-   |       ---------------- this trait cannot be made into an object...
+   |       ---------------- this trait is not dyn compatible...
 LL |     fn static_fn() {}
    |        ^^^^^^^^^ ...because associated function `static_fn` has no `self` parameter
 help: consider turning `static_fn` into a method by giving it a `&self` argument
@@ -34,49 +36,52 @@ help: alternatively, consider constraining `static_fn` so it does not apply to t
 LL |     fn static_fn() where Self: Sized {}
    |                    +++++++++++++++++
 
-error[E0038]: the trait `DynIncompatible3` cannot be made into an object
+error[E0038]: the trait `DynIncompatible3` is not dyn compatible
   --> $DIR/feature-gate-dyn_compatible_for_dispatch.rs:27:40
    |
 LL | fn takes_dyn_incompatible_box(obj: Box<dyn DynIncompatible3>) {
-   |                                        ^^^^^^^^^^^^^^^^^^^^ `DynIncompatible3` cannot be made into an object
+   |                                        ^^^^^^^^^^^^^^^^^^^^ `DynIncompatible3` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/feature-gate-dyn_compatible_for_dispatch.rs:11:8
    |
 LL | trait DynIncompatible3 {
-   |       ---------------- this trait cannot be made into an object...
+   |       ---------------- this trait is not dyn compatible...
 LL |     fn foo<T>(&self);
    |        ^^^ ...because method `foo` has generic type parameters
    = help: consider moving `foo` to another trait
 
-error[E0038]: the trait `DynIncompatible4` cannot be made into an object
+error[E0038]: the trait `DynIncompatible4` is not dyn compatible
   --> $DIR/feature-gate-dyn_compatible_for_dispatch.rs:31:48
    |
 LL | fn return_dyn_incompatible_rc() -> std::rc::Rc<dyn DynIncompatible4> {
-   |                                                ^^^^^^^^^^^^^^^^^^^^ `DynIncompatible4` cannot be made into an object
+   |                                                ^^^^^^^^^^^^^^^^^^^^ `DynIncompatible4` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/feature-gate-dyn_compatible_for_dispatch.rs:15:22
    |
 LL | trait DynIncompatible4 {
-   |       ---------------- this trait cannot be made into an object...
+   |       ---------------- this trait is not dyn compatible...
 LL |     fn foo(&self, s: &Self);
    |                      ^^^^^ ...because method `foo` references the `Self` type in this parameter
    = help: consider moving `foo` to another trait
 
-error[E0038]: the trait `DynIncompatible1` cannot be made into an object
+error[E0038]: the trait `DynIncompatible1` is not dyn compatible
   --> $DIR/feature-gate-dyn_compatible_for_dispatch.rs:38:16
    |
 LL | impl Trait for dyn DynIncompatible1 {}
-   |                ^^^^^^^^^^^^^^^^^^^^ `DynIncompatible1` cannot be made into an object
+   |                ^^^^^^^^^^^^^^^^^^^^ `DynIncompatible1` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/feature-gate-dyn_compatible_for_dispatch.rs:4:25
    |
 LL | trait DynIncompatible1: Sized {}
    |       ----------------  ^^^^^ ...because it requires `Self: Sized`
    |       |
-   |       this trait cannot be made into an object...
+   |       this trait is not dyn compatible...
 
 error: aborting due to 5 previous errors
 

tests/ui/generic-associated-types/gat-in-trait-path-undeclared-lifetime.rs

@@ -8,5 +8,5 @@ fn _f(arg : Box<dyn for<'a> X<Y<'x> = &'a [u32]>>) {}
     //~| ERROR: binding for associated type `Y` references lifetime
     //~| ERROR: binding for associated type `Y` references lifetime
     //~| ERROR: binding for associated type `Y` references lifetime
-    //~| ERROR: the trait `X` cannot be made into an object
+    //~| ERROR: the trait `X` is not dyn compatible
 }

tests/ui/generic-associated-types/gat-in-trait-path-undeclared-lifetime.stderr

@@ -36,17 +36,18 @@ LL |   fn _f(arg : Box<dyn for<'a> X<Y<'x> = &'a [u32]>>) {}
    |
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error[E0038]: the trait `X` cannot be made into an object
+error[E0038]: the trait `X` is not dyn compatible
   --> $DIR/gat-in-trait-path-undeclared-lifetime.rs:6:19
    |
 LL |   fn _f(arg : Box<dyn for<'a> X<Y<'x> = &'a [u32]>>) {}
-   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `X` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/gat-in-trait-path-undeclared-lifetime.rs:2:8
    |
 LL | trait X {
-   |       - this trait cannot be made into an object...
+   |       - this trait is not dyn compatible...
 LL |   type Y<'x>;
    |        ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait

tests/ui/generic-associated-types/gat-in-trait-path.base.stderr

@@ -1,56 +1,50 @@
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/gat-in-trait-path.rs:26:17
    |
 LL | fn f(_arg : Box<dyn for<'a> Foo<A<'a> = &'a ()>>) {}
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/gat-in-trait-path.rs:10:10
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     type A<'a> where Self: 'a;
    |          ^ ...because it contains the generic associated type `A`
    = help: consider moving `A` to another trait
-   = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Foo` for this new enum and using it instead:
-             Fooy
-             Fooer<T>
 
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/gat-in-trait-path.rs:32:5
    |
 LL |   f(Box::new(foo));
-   |     ^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |     ^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/gat-in-trait-path.rs:10:10
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     type A<'a> where Self: 'a;
    |          ^ ...because it contains the generic associated type `A`
    = help: consider moving `A` to another trait
-   = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Foo` for this new enum and using it instead:
-             Fooy
-             Fooer<T>
 
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/gat-in-trait-path.rs:32:5
    |
 LL |   f(Box::new(foo));
-   |     ^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |     ^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/gat-in-trait-path.rs:10:10
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     type A<'a> where Self: 'a;
    |          ^ ...because it contains the generic associated type `A`
    = help: consider moving `A` to another trait
-   = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Foo` for this new enum and using it instead:
-             Fooy
-             Fooer<T>
    = note: required for the cast from `Box<Fooer<{integer}>>` to `Box<(dyn Foo<A<'a> = &'a ()> + 'static)>`
 
 error: aborting due to 3 previous errors

tests/ui/generic-associated-types/gat-in-trait-path.rs

@@ -20,12 +20,11 @@ impl<T> Foo for Fooer<T> {
 }
 
 fn f(_arg : Box<dyn for<'a> Foo<A<'a> = &'a ()>>) {}
-//~^ the trait `Foo` cannot be made into an object
-
+//~^ the trait `Foo` is not dyn compatible
 
 fn main() {
   let foo = Fooer(5);
   f(Box::new(foo));
-  //~^ the trait `Foo` cannot be made into an object
-  //~| the trait `Foo` cannot be made into an object
+  //~^ the trait `Foo` is not dyn compatible
+  //~| the trait `Foo` is not dyn compatible
 }

tests/ui/generic-associated-types/gat-in-trait-path.stderr

@@ -1,56 +1,50 @@
-error[E0038]: the trait `Foo` cannot be made into an object
+error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/gat-in-trait-path.rs:22:17
    |
 LL | fn f(_arg : Box<dyn for<'a> Foo<A<'a> = &'a ()>>) {}
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/gat-in-trait-path.rs:6:10
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     type A<'a> where Self: 'a;
    |          ^ ...because it contains the generic associated type `A`
    = help: consider moving `A` to another trait
-   = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Foo` for this new enum and using it instead:
-             Fooy
-             Fooer<T>
 
-error[E0038]: the trait `Foo` cannot be made into an object
-  --> $DIR/gat-in-trait-path.rs:28:5
+error[E0038]: the trait `Foo` is not dyn compatible
+  --> $DIR/gat-in-trait-path.rs:27:5
    |
 LL |   f(Box::new(foo));
-   |     ^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |     ^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/gat-in-trait-path.rs:6:10
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     type A<'a> where Self: 'a;
    |          ^ ...because it contains the generic associated type `A`
    = help: consider moving `A` to another trait
-   = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Foo` for this new enum and using it instead:
-             Fooy
-             Fooer<T>
 
-error[E0038]: the trait `Foo` cannot be made into an object
-  --> $DIR/gat-in-trait-path.rs:28:5
+error[E0038]: the trait `Foo` is not dyn compatible
+  --> $DIR/gat-in-trait-path.rs:27:5
    |
 LL |   f(Box::new(foo));
-   |     ^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |     ^^^^^^^^^^^^^ `Foo` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/gat-in-trait-path.rs:6:10
    |
 LL | trait Foo {
-   |       --- this trait cannot be made into an object...
+   |       --- this trait is not dyn compatible...
 LL |     type A<'a> where Self: 'a;
    |          ^ ...because it contains the generic associated type `A`
    = help: consider moving `A` to another trait
-   = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Foo` for this new enum and using it instead:
-             Fooy
-             Fooer<T>
    = note: required for the cast from `Box<Fooer<{integer}>>` to `Box<(dyn Foo<A<'a> = &'a ()> + 'static)>`
 
 error: aborting due to 3 previous errors

tests/ui/generic-associated-types/gat-trait-path-parenthesised-args.rs

@@ -12,7 +12,7 @@ fn foo<'a>(arg: Box<dyn X<Y('a) = &'a ()>>) {}
   //~| ERROR associated type takes 0 generic arguments but 1 generic argument
   //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
   //~| ERROR at least one trait is required
-  //~| ERROR: the trait `X` cannot be made into an object
+  //~| ERROR: the trait `X` is not dyn compatible
 
 
 fn bar<'a>(arg: Box<dyn X<Y() = ()>>) {}
@@ -20,6 +20,6 @@ fn bar<'a>(arg: Box<dyn X<Y() = ()>>) {}
   //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
   //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
   //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
-  //~| ERROR: the trait `X` cannot be made into an object
+  //~| ERROR: the trait `X` is not dyn compatible
 
 fn main() {}

tests/ui/generic-associated-types/gat-trait-path-parenthesised-args.stderr

@@ -123,17 +123,18 @@ error[E0224]: at least one trait is required for an object type
 LL | fn foo<'a>(arg: Box<dyn X<Y('a) = &'a ()>>) {}
    |                             ^^
 
-error[E0038]: the trait `X` cannot be made into an object
+error[E0038]: the trait `X` is not dyn compatible
   --> $DIR/gat-trait-path-parenthesised-args.rs:5:21
    |
 LL | fn foo<'a>(arg: Box<dyn X<Y('a) = &'a ()>>) {}
-   |                     ^^^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |                     ^^^^^^^^^^^^^^^^^^^^^ `X` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/gat-trait-path-parenthesised-args.rs:2:8
    |
 LL | trait X {
-   |       - this trait cannot be made into an object...
+   |       - this trait is not dyn compatible...
 LL |   type Y<'a>;
    |        ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait
@@ -188,17 +189,18 @@ help: add missing lifetime argument
 LL | fn bar<'a>(arg: Box<dyn X<Y('_) = ()>>) {}
    |                             ++
 
-error[E0038]: the trait `X` cannot be made into an object
+error[E0038]: the trait `X` is not dyn compatible
   --> $DIR/gat-trait-path-parenthesised-args.rs:18:21
    |
 LL | fn bar<'a>(arg: Box<dyn X<Y() = ()>>) {}
-   |                     ^^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |                     ^^^^^^^^^^^^^^^ `X` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/gat-trait-path-parenthesised-args.rs:2:8
    |
 LL | trait X {
-   |       - this trait cannot be made into an object...
+   |       - this trait is not dyn compatible...
 LL |   type Y<'a>;
    |        ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait

tests/ui/generic-associated-types/issue-67510-pass.base.stderr

@@ -1,14 +1,15 @@
-error[E0038]: the trait `X` cannot be made into an object
+error[E0038]: the trait `X` is not dyn compatible
   --> $DIR/issue-67510-pass.rs:12:23
    |
 LL | fn _func1<'a>(_x: Box<dyn X<Y<'a>=&'a ()>>) {}
-   |                       ^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |                       ^^^^^^^^^^^^^^^^^^^ `X` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-67510-pass.rs:9:10
    |
 LL | trait X {
-   |       - this trait cannot be made into an object...
+   |       - this trait is not dyn compatible...
 LL |     type Y<'a>;
    |          ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait

tests/ui/generic-associated-types/issue-67510-pass.rs

@@ -5,6 +5,6 @@ trait X {
 }
 
 fn _func1<'a>(_x: Box<dyn X<Y<'a>=&'a ()>>) {}
-//~^ ERROR the trait `X` cannot be made into an object
+//~^ ERROR the trait `X` is not dyn compatible
 
 fn main() {}

tests/ui/generic-associated-types/issue-67510-pass.stderr

@@ -1,14 +1,15 @@
-error[E0038]: the trait `X` cannot be made into an object
+error[E0038]: the trait `X` is not dyn compatible
   --> $DIR/issue-67510-pass.rs:7:23
    |
 LL | fn _func1<'a>(_x: Box<dyn X<Y<'a>=&'a ()>>) {}
-   |                       ^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |                       ^^^^^^^^^^^^^^^^^^^ `X` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-67510-pass.rs:4:10
    |
 LL | trait X {
-   |       - this trait cannot be made into an object...
+   |       - this trait is not dyn compatible...
 LL |     type Y<'a>;
    |          ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait

tests/ui/generic-associated-types/issue-67510.rs

@@ -5,6 +5,6 @@ trait X {
 fn f(x: Box<dyn X<Y<'a> = &'a ()>>) {}
 //~^ ERROR: use of undeclared lifetime name `'a`
 //~| ERROR: use of undeclared lifetime name `'a`
-//~| ERROR: the trait `X` cannot be made into an object [E0038]
+//~| ERROR: the trait `X` is not dyn compatible [E0038]
 
 fn main() {}

tests/ui/generic-associated-types/issue-67510.stderr

@@ -29,17 +29,18 @@ help: consider introducing lifetime `'a` here
 LL | fn f<'a>(x: Box<dyn X<Y<'a> = &'a ()>>) {}
    |     ++++
 
-error[E0038]: the trait `X` cannot be made into an object
+error[E0038]: the trait `X` is not dyn compatible
   --> $DIR/issue-67510.rs:5:13
    |
 LL | fn f(x: Box<dyn X<Y<'a> = &'a ()>>) {}
-   |             ^^^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |             ^^^^^^^^^^^^^^^^^^^^^ `X` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-67510.rs:2:10
    |
 LL | trait X {
-   |       - this trait cannot be made into an object...
+   |       - this trait is not dyn compatible...
 LL |     type Y<'a>;
    |          ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait

tests/ui/generic-associated-types/issue-71176.rs

@@ -11,13 +11,13 @@ struct Holder<B> {
   //~^ ERROR: missing generics for associated type
   //~| ERROR: missing generics for associated type
   //~| ERROR: missing generics for associated type
-  //~| ERROR: the trait `Provider` cannot be made into an object
+  //~| ERROR: the trait `Provider` is not dyn compatible
 }
 
 fn main() {
     Holder {
         inner: Box::new(()),
-        //~^ ERROR: the trait `Provider` cannot be made into an object
-        //~| ERROR: the trait `Provider` cannot be made into an object
+        //~^ ERROR: the trait `Provider` is not dyn compatible
+        //~| ERROR: the trait `Provider` is not dyn compatible
     };
 }

tests/ui/generic-associated-types/issue-71176.stderr

@@ -48,53 +48,56 @@ help: add missing lifetime argument
 LL |   inner: Box<dyn Provider<A<'a> = B>>,
    |                            ++++
 
-error[E0038]: the trait `Provider` cannot be made into an object
+error[E0038]: the trait `Provider` is not dyn compatible
   --> $DIR/issue-71176.rs:10:14
    |
 LL |   inner: Box<dyn Provider<A = B>>,
-   |              ^^^^^^^^^^^^^^^^^^^ `Provider` cannot be made into an object
+   |              ^^^^^^^^^^^^^^^^^^^ `Provider` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-71176.rs:2:10
    |
 LL | trait Provider {
-   |       -------- this trait cannot be made into an object...
+   |       -------- this trait is not dyn compatible...
 LL |     type A<'a>;
    |          ^ ...because it contains the generic associated type `A`
    = help: consider moving `A` to another trait
-   = help: only type `()` implements the trait, consider using it directly instead
+   = help: only type `()` implements `Provider`; consider using it directly instead.
 
-error[E0038]: the trait `Provider` cannot be made into an object
+error[E0038]: the trait `Provider` is not dyn compatible
   --> $DIR/issue-71176.rs:19:16
    |
 LL |         inner: Box::new(()),
-   |                ^^^^^^^^^^^^ `Provider` cannot be made into an object
+   |                ^^^^^^^^^^^^ `Provider` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-71176.rs:2:10
    |
 LL | trait Provider {
-   |       -------- this trait cannot be made into an object...
+   |       -------- this trait is not dyn compatible...
 LL |     type A<'a>;
    |          ^ ...because it contains the generic associated type `A`
    = help: consider moving `A` to another trait
-   = help: only type `()` implements the trait, consider using it directly instead
+   = help: only type `()` implements `Provider`; consider using it directly instead.
 
-error[E0038]: the trait `Provider` cannot be made into an object
+error[E0038]: the trait `Provider` is not dyn compatible
   --> $DIR/issue-71176.rs:19:16
    |
 LL |         inner: Box::new(()),
-   |                ^^^^^^^^^^^^ `Provider` cannot be made into an object
+   |                ^^^^^^^^^^^^ `Provider` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-71176.rs:2:10
    |
 LL | trait Provider {
-   |       -------- this trait cannot be made into an object...
+   |       -------- this trait is not dyn compatible...
 LL |     type A<'a>;
    |          ^ ...because it contains the generic associated type `A`
    = help: consider moving `A` to another trait
-   = help: only type `()` implements the trait, consider using it directly instead
+   = help: only type `()` implements `Provider`; consider using it directly instead.
    = note: required for the cast from `Box<()>` to `Box<(dyn Provider<A<'_> = _> + 'static), {type error}>`
 
 error: aborting due to 6 previous errors

tests/ui/generic-associated-types/issue-76535.base.stderr

@@ -14,39 +14,41 @@ help: add missing lifetime argument
 LL |     let sub: Box<dyn SuperTrait<SubType<'a> = SubStruct>> = Box::new(SuperStruct::new(0));
    |                                        ++++
 
-error[E0038]: the trait `SuperTrait` cannot be made into an object
+error[E0038]: the trait `SuperTrait` is not dyn compatible
   --> $DIR/issue-76535.rs:39:14
    |
 LL |     let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` cannot be made into an object
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-76535.rs:9:10
    |
 LL | pub trait SuperTrait {
-   |           ---------- this trait cannot be made into an object...
+   |           ---------- this trait is not dyn compatible...
 LL |     type SubType<'a>: SubTrait where Self: 'a;
    |          ^^^^^^^ ...because it contains the generic associated type `SubType`
    = help: consider moving `SubType` to another trait
-   = help: only type `SuperStruct` is seen to implement the trait in this crate, consider using it directly instead
-   = note: `SuperTrait` can be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type
+   = help: only type `SuperStruct` implements `SuperTrait` within this crate. Consider using it directly instead.
+   = note: `SuperTrait` may be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type
 
-error[E0038]: the trait `SuperTrait` cannot be made into an object
+error[E0038]: the trait `SuperTrait` is not dyn compatible
   --> $DIR/issue-76535.rs:39:57
    |
 LL |     let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
-   |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` cannot be made into an object
+   |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-76535.rs:9:10
    |
 LL | pub trait SuperTrait {
-   |           ---------- this trait cannot be made into an object...
+   |           ---------- this trait is not dyn compatible...
 LL |     type SubType<'a>: SubTrait where Self: 'a;
    |          ^^^^^^^ ...because it contains the generic associated type `SubType`
    = help: consider moving `SubType` to another trait
-   = help: only type `SuperStruct` is seen to implement the trait in this crate, consider using it directly instead
-   = note: `SuperTrait` can be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type
+   = help: only type `SuperStruct` implements `SuperTrait` within this crate. Consider using it directly instead.
+   = note: `SuperTrait` may be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type
    = note: required for the cast from `Box<SuperStruct>` to `Box<dyn SuperTrait<SubType<'_> = SubStruct<'_>>>`
 
 error: aborting due to 3 previous errors

tests/ui/generic-associated-types/issue-76535.stderr

@@ -14,39 +14,41 @@ help: add missing lifetime argument
 LL |     let sub: Box<dyn SuperTrait<SubType<'a> = SubStruct>> = Box::new(SuperStruct::new(0));
    |                                        ++++
 
-error[E0038]: the trait `SuperTrait` cannot be made into an object
+error[E0038]: the trait `SuperTrait` is not dyn compatible
   --> $DIR/issue-76535.rs:34:14
    |
 LL |     let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` cannot be made into an object
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-76535.rs:4:10
    |
 LL | pub trait SuperTrait {
-   |           ---------- this trait cannot be made into an object...
+   |           ---------- this trait is not dyn compatible...
 LL |     type SubType<'a>: SubTrait where Self: 'a;
    |          ^^^^^^^ ...because it contains the generic associated type `SubType`
    = help: consider moving `SubType` to another trait
-   = help: only type `SuperStruct` is seen to implement the trait in this crate, consider using it directly instead
-   = note: `SuperTrait` can be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type
+   = help: only type `SuperStruct` implements `SuperTrait` within this crate; consider using it directly instead.
+   = note: `SuperTrait` may be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type
 
-error[E0038]: the trait `SuperTrait` cannot be made into an object
+error[E0038]: the trait `SuperTrait` is not dyn compatible
   --> $DIR/issue-76535.rs:34:57
    |
 LL |     let sub: Box<dyn SuperTrait<SubType = SubStruct>> = Box::new(SuperStruct::new(0));
-   |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` cannot be made into an object
+   |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SuperTrait` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-76535.rs:4:10
    |
 LL | pub trait SuperTrait {
-   |           ---------- this trait cannot be made into an object...
+   |           ---------- this trait is not dyn compatible...
 LL |     type SubType<'a>: SubTrait where Self: 'a;
    |          ^^^^^^^ ...because it contains the generic associated type `SubType`
    = help: consider moving `SubType` to another trait
-   = help: only type `SuperStruct` is seen to implement the trait in this crate, consider using it directly instead
-   = note: `SuperTrait` can be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type
+   = help: only type `SuperStruct` implements `SuperTrait` within this crate; consider using it directly instead.
+   = note: `SuperTrait` may be implemented in other crates; if you want to support your users passing their own types here, you can't refer to a specific type
    = note: required for the cast from `Box<SuperStruct>` to `Box<dyn SuperTrait<SubType<'_> = SubStruct<'_>>>`
 
 error: aborting due to 3 previous errors

tests/ui/generic-associated-types/issue-78671.base.stderr

@@ -14,17 +14,18 @@ help: add missing generic argument
 LL |     Box::new(Family) as &dyn CollectionFamily<Member<T>=usize>
    |                                                     +++
 
-error[E0038]: the trait `CollectionFamily` cannot be made into an object
+error[E0038]: the trait `CollectionFamily` is not dyn compatible
   --> $DIR/issue-78671.rs:10:25
    |
 LL |     Box::new(Family) as &dyn CollectionFamily<Member=usize>
-   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `CollectionFamily` cannot be made into an object
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `CollectionFamily` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-78671.rs:7:10
    |
 LL | trait CollectionFamily {
-   |       ---------------- this trait cannot be made into an object...
+   |       ---------------- this trait is not dyn compatible...
 LL |     type Member<T>;
    |          ^^^^^^ ...because it contains the generic associated type `Member`
    = help: consider moving `Member` to another trait

tests/ui/generic-associated-types/issue-78671.rs

@@ -4,7 +4,7 @@ trait CollectionFamily {
 fn floatify() {
     Box::new(Family) as &dyn CollectionFamily<Member=usize>
     //~^ ERROR: missing generics for associated type
-    //~| ERROR: the trait `CollectionFamily` cannot be made into an object
+    //~| ERROR: the trait `CollectionFamily` is not dyn compatible
 }
 
 struct Family;

tests/ui/generic-associated-types/issue-78671.stderr

@@ -14,17 +14,18 @@ help: add missing generic argument
 LL |     Box::new(Family) as &dyn CollectionFamily<Member<T>=usize>
    |                                                     +++
 
-error[E0038]: the trait `CollectionFamily` cannot be made into an object
+error[E0038]: the trait `CollectionFamily` is not dyn compatible
   --> $DIR/issue-78671.rs:5:25
    |
 LL |     Box::new(Family) as &dyn CollectionFamily<Member=usize>
-   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `CollectionFamily` cannot be made into an object
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `CollectionFamily` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-78671.rs:2:10
    |
 LL | trait CollectionFamily {
-   |       ---------------- this trait cannot be made into an object...
+   |       ---------------- this trait is not dyn compatible...
 LL |     type Member<T>;
    |          ^^^^^^ ...because it contains the generic associated type `Member`
    = help: consider moving `Member` to another trait

tests/ui/generic-associated-types/issue-79422.base.stderr

@@ -14,41 +14,37 @@ help: add missing lifetime argument
 LL |         as Box<dyn MapLike<u8, u8, VRefCont<'a> = dyn RefCont<'_, u8>>>;
    |                                            ++++
 
-error[E0038]: the trait `MapLike` cannot be made into an object
+error[E0038]: the trait `MapLike` is not dyn compatible
   --> $DIR/issue-79422.rs:47:12
    |
 LL |         as Box<dyn MapLike<u8, u8, VRefCont = dyn RefCont<'_, u8>>>;
-   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` cannot be made into an object
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-79422.rs:23:10
    |
 LL | trait MapLike<K, V> {
-   |       ------- this trait cannot be made into an object...
+   |       ------- this trait is not dyn compatible...
 LL |     type VRefCont<'a>: RefCont<'a, V> where Self: 'a;
    |          ^^^^^^^^ ...because it contains the generic associated type `VRefCont`
    = help: consider moving `VRefCont` to another trait
-   = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `MapLike` for this new enum and using it instead:
-             std::collections::BTreeMap<K, V>
-             Source
 
-error[E0038]: the trait `MapLike` cannot be made into an object
+error[E0038]: the trait `MapLike` is not dyn compatible
   --> $DIR/issue-79422.rs:44:13
    |
 LL |     let m = Box::new(std::collections::BTreeMap::<u8, u8>::new())
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` cannot be made into an object
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-79422.rs:23:10
    |
 LL | trait MapLike<K, V> {
-   |       ------- this trait cannot be made into an object...
+   |       ------- this trait is not dyn compatible...
 LL |     type VRefCont<'a>: RefCont<'a, V> where Self: 'a;
    |          ^^^^^^^^ ...because it contains the generic associated type `VRefCont`
    = help: consider moving `VRefCont` to another trait
-   = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `MapLike` for this new enum and using it instead:
-             std::collections::BTreeMap<K, V>
-             Source
    = note: required for the cast from `Box<BTreeMap<u8, u8>>` to `Box<dyn MapLike<u8, u8, VRefCont<'_> = (dyn RefCont<'_, u8> + 'static)>>`
 
 error: aborting due to 3 previous errors

tests/ui/generic-associated-types/issue-79422.stderr

@@ -14,41 +14,37 @@ help: add missing lifetime argument
 LL |         as Box<dyn MapLike<u8, u8, VRefCont<'a> = dyn RefCont<'_, u8>>>;
    |                                            ++++
 
-error[E0038]: the trait `MapLike` cannot be made into an object
+error[E0038]: the trait `MapLike` is not dyn compatible
   --> $DIR/issue-79422.rs:41:12
    |
 LL |         as Box<dyn MapLike<u8, u8, VRefCont = dyn RefCont<'_, u8>>>;
-   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` cannot be made into an object
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-79422.rs:18:10
    |
 LL | trait MapLike<K, V> {
-   |       ------- this trait cannot be made into an object...
+   |       ------- this trait is not dyn compatible...
 LL |     type VRefCont<'a>: RefCont<'a, V> where Self: 'a;
    |          ^^^^^^^^ ...because it contains the generic associated type `VRefCont`
    = help: consider moving `VRefCont` to another trait
-   = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `MapLike` for this new enum and using it instead:
-             std::collections::BTreeMap<K, V>
-             Source
 
-error[E0038]: the trait `MapLike` cannot be made into an object
+error[E0038]: the trait `MapLike` is not dyn compatible
   --> $DIR/issue-79422.rs:39:13
    |
 LL |     let m = Box::new(std::collections::BTreeMap::<u8, u8>::new())
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` cannot be made into an object
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MapLike` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/issue-79422.rs:18:10
    |
 LL | trait MapLike<K, V> {
-   |       ------- this trait cannot be made into an object...
+   |       ------- this trait is not dyn compatible...
 LL |     type VRefCont<'a>: RefCont<'a, V> where Self: 'a;
    |          ^^^^^^^^ ...because it contains the generic associated type `VRefCont`
    = help: consider moving `VRefCont` to another trait
-   = help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `MapLike` for this new enum and using it instead:
-             std::collections::BTreeMap<K, V>
-             Source
    = note: required for the cast from `Box<BTreeMap<u8, u8>>` to `Box<dyn MapLike<u8, u8, VRefCont<'_> = (dyn RefCont<'_, u8> + 'static)>>`
 
 error: aborting due to 3 previous errors

tests/ui/generic-associated-types/missing_lifetime_args.rs

@@ -12,7 +12,7 @@ fn foo<'c, 'd>(_arg: Box<dyn X<Y = (&'c u32, &'d u32)>>) {}
 //~^ ERROR missing generics for associated type
 //~| ERROR missing generics for associated type
 //~| ERROR missing generics for associated type
-//~| ERROR the trait `X` cannot be made into an object
+//~| ERROR the trait `X` is not dyn compatible
 
 fn bar<'a, 'b, 'c>(_arg: Foo<'a, 'b>) {}
 //~^ ERROR struct takes 3 lifetime arguments but 2 lifetime

tests/ui/generic-associated-types/missing_lifetime_args.stderr

@@ -48,17 +48,18 @@ help: add missing lifetime arguments
 LL | fn foo<'c, 'd>(_arg: Box<dyn X<Y<'_, '_> = (&'c u32, &'d u32)>>) {}
    |                                 ++++++++
 
-error[E0038]: the trait `X` cannot be made into an object
+error[E0038]: the trait `X` is not dyn compatible
   --> $DIR/missing_lifetime_args.rs:11:26
    |
 LL | fn foo<'c, 'd>(_arg: Box<dyn X<Y = (&'c u32, &'d u32)>>) {}
-   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `X` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/missing_lifetime_args.rs:2:10
    |
 LL | trait X {
-   |       - this trait cannot be made into an object...
+   |       - this trait is not dyn compatible...
 LL |     type Y<'a, 'b>;
    |          ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait

tests/ui/generic-associated-types/parse/trait-path-type-error-once-implemented.rs

@@ -10,7 +10,7 @@ fn f2<'a>(arg : Box<dyn X<Y<1> = &'a ()>>) {}
       //~| ERROR associated type takes 0 generic arguments but 1 generic argument
       //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
       //~| ERROR associated type takes 0 generic arguments but 1 generic argument
-      //~| ERROR the trait `X` cannot be made into an object
+      //~| ERROR the trait `X` is not dyn compatible
 };
 
 fn main() {}

tests/ui/generic-associated-types/parse/trait-path-type-error-once-implemented.stderr

@@ -92,17 +92,18 @@ LL |     type Y<'a>;
    |          ^
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error[E0038]: the trait `X` cannot be made into an object
+error[E0038]: the trait `X` is not dyn compatible
   --> $DIR/trait-path-type-error-once-implemented.rs:6:23
    |
 LL |   fn f2<'a>(arg : Box<dyn X<Y<1> = &'a ()>>) {}
-   |                       ^^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |                       ^^^^^^^^^^^^^^^^^^^^ `X` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/trait-path-type-error-once-implemented.rs:2:10
    |
 LL | trait X {
-   |       - this trait cannot be made into an object...
+   |       - this trait is not dyn compatible...
 LL |     type Y<'a>;
    |          ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait

tests/ui/generic-associated-types/trait-objects.base.stderr

@@ -1,44 +1,47 @@
-error[E0038]: the trait `StreamingIterator` cannot be made into an object
+error[E0038]: the trait `StreamingIterator` is not dyn compatible
   --> $DIR/trait-objects.rs:13:21
    |
 LL | fn min_size(x: &mut dyn for<'a> StreamingIterator<Item<'a> = &'a i32>) -> usize {
-   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `StreamingIterator` cannot be made into an object
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `StreamingIterator` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/trait-objects.rs:7:10
    |
 LL | trait StreamingIterator {
-   |       ----------------- this trait cannot be made into an object...
+   |       ----------------- this trait is not dyn compatible...
 LL |     type Item<'a> where Self: 'a;
    |          ^^^^ ...because it contains the generic associated type `Item`
    = help: consider moving `Item` to another trait
 
-error[E0038]: the trait `StreamingIterator` cannot be made into an object
+error[E0038]: the trait `StreamingIterator` is not dyn compatible
   --> $DIR/trait-objects.rs:15:7
    |
 LL |     x.size_hint().0
-   |       ^^^^^^^^^ `StreamingIterator` cannot be made into an object
+   |       ^^^^^^^^^ `StreamingIterator` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/trait-objects.rs:7:10
    |
 LL | trait StreamingIterator {
-   |       ----------------- this trait cannot be made into an object...
+   |       ----------------- this trait is not dyn compatible...
 LL |     type Item<'a> where Self: 'a;
    |          ^^^^ ...because it contains the generic associated type `Item`
    = help: consider moving `Item` to another trait
 
-error[E0038]: the trait `StreamingIterator` cannot be made into an object
+error[E0038]: the trait `StreamingIterator` is not dyn compatible
   --> $DIR/trait-objects.rs:15:5
    |
 LL |     x.size_hint().0
-   |     ^^^^^^^^^^^^^ `StreamingIterator` cannot be made into an object
+   |     ^^^^^^^^^^^^^ `StreamingIterator` is not dyn compatible
    |
-note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/trait-objects.rs:7:10
    |
 LL | trait StreamingIterator {
-   |       ----------------- this trait cannot be made into an object...
+   |       ----------------- this trait is not dyn compatible...
 LL |     type Item<'a> where Self: 'a;
    |          ^^^^ ...because it contains the generic associated type `Item`
    = help: consider moving `Item` to another trait