rust-lang · estebank · Jan 12, 2026 · Jan 12, 2026 · Jan 13, 2026 · Jan 13, 2026
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
@@ -681,7 +681,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     // Ambiguous predicates should never error
                     | ty::PredicateKind::Ambiguous
                     // We never return Err when proving UnstableFeature goal.
-                    | ty::PredicateKind::Clause(ty::ClauseKind::UnstableFeature{ .. })
+                    | ty::PredicateKind::Clause(ty::ClauseKind::UnstableFeature { .. })
                     | ty::PredicateKind::NormalizesTo { .. }
                     | ty::PredicateKind::AliasRelate { .. }
                     | ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType { .. }) => {

diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -5515,7 +5515,14 @@ pub(super) fn get_explanation_based_on_obligation<'tcx>(
         };
         if let ty::PredicatePolarity::Positive = trait_predicate.polarity() {
             format!(
-                "{pre_message}the trait `{}` is not implemented for{desc} `{}`",
+                "{pre_message}the {}trait `{}` is not implemented for{desc} `{}`",
+                if tcx.lookup_stability(trait_predicate.def_id()).map(|s| s.level.is_stable())
+                    == Some(false)
+                {
+                    "nightly-only, unstable "
+                } else {
+                    ""
+                },
                 trait_predicate.print_modifiers_and_trait_path(),
                 tcx.short_string(trait_predicate.self_ty().skip_binder(), long_ty_path),
             )

diff --git a/library/core/src/iter/range.rs b/library/core/src/iter/range.rs
@@ -21,6 +21,13 @@ unsafe_impl_trusted_step![AsciiChar char i8 i16 i32 i64 i128 isize u8 u16 u32 u6
 /// The *successor* operation moves towards values that compare greater.
 /// The *predecessor* operation moves towards values that compare lesser.
 #[rustc_diagnostic_item = "range_step"]
+#[rustc_on_unimplemented(
+    message = "`std::ops::Range<{Self}>` is not an iterator",
+    label = "`Range<{Self}>` is not an iterator",
+    note = "`Range` only implements `Iterator` for select types in the standard library, \
+            particularly integers; to see the full list of types, see the documentation for the \
+            unstable `Step` trait"
+)]
 #[unstable(feature = "step_trait", issue = "42168")]
 pub trait Step: Clone + PartialOrd + Sized {
     /// Returns the bounds on the number of *successor* steps required to get from `start` to `end`

diff --git a/tests/run-make/missing-unstable-trait-bound/missing-bound.stderr b/tests/run-make/missing-unstable-trait-bound/missing-bound.stderr
@@ -1,9 +1,10 @@
-error[E0277]: the trait bound `T: Step` is not satisfied
+error[E0277]: `std::ops::Range<T>` is not an iterator
  --> missing-bound.rs:2:14
   |
 2 |     for _ in t {}
-  |              ^ the trait `Step` is not implemented for `T`
+  |              ^ `Range<T>` is not an iterator
   |
+  = note: `Range` only implements `Iterator` for select types in the standard library, particularly integers; to see the full list of types, see the documentation for the unstable `Step` trait
   = note: required for `std::ops::Range<T>` to implement `Iterator`
   = note: required for `std::ops::Range<T>` to implement `IntoIterator`
 

diff --git a/tests/ui-fulldeps/rustc-dev-remap.only-remap.stderr b/tests/ui-fulldeps/rustc-dev-remap.only-remap.stderr
@@ -4,7 +4,7 @@ error[E0277]: the trait bound `NotAValidResultType: VisitorResult` is not satisf
 LL |     type Result = NotAValidResultType;
    |                   ^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `VisitorResult` is not implemented for `NotAValidResultType`
+help: the nightly-only, unstable trait `VisitorResult` is not implemented for `NotAValidResultType`
   --> $DIR/rustc-dev-remap.rs:LL:COL
    |
 LL | struct NotAValidResultType;

diff --git a/tests/ui-fulldeps/rustc-dev-remap.remap-unremap.stderr b/tests/ui-fulldeps/rustc-dev-remap.remap-unremap.stderr
@@ -4,7 +4,7 @@ error[E0277]: the trait bound `NotAValidResultType: VisitorResult` is not satisf
 LL |     type Result = NotAValidResultType;
    |                   ^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `VisitorResult` is not implemented for `NotAValidResultType`
+help: the nightly-only, unstable trait `VisitorResult` is not implemented for `NotAValidResultType`
   --> $DIR/rustc-dev-remap.rs:LL:COL
    |
 LL | struct NotAValidResultType;

diff --git a/tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.stderr b/tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.stderr
@@ -7,7 +7,7 @@ LL | #[derive(Diagnostic)]
 LL |     arg: NotIntoDiagArg,
    |          ^^^^^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `IntoDiagArg` is not implemented for `NotIntoDiagArg`
+help: the nightly-only, unstable trait `IntoDiagArg` is not implemented for `NotIntoDiagArg`
   --> $DIR/diagnostic-derive-doc-comment-field.rs:28:1
    |
 LL | struct NotIntoDiagArg;
@@ -29,7 +29,7 @@ LL | #[derive(Subdiagnostic)]
 LL |     arg: NotIntoDiagArg,
    |          ^^^^^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `IntoDiagArg` is not implemented for `NotIntoDiagArg`
+help: the nightly-only, unstable trait `IntoDiagArg` is not implemented for `NotIntoDiagArg`
   --> $DIR/diagnostic-derive-doc-comment-field.rs:28:1
    |
 LL | struct NotIntoDiagArg;

diff --git a/tests/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr b/tests/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr
@@ -657,7 +657,7 @@ LL | #[derive(Diagnostic)]
 LL |     other: Hello,
    |            ^^^^^ unsatisfied trait bound
    |
-help: the trait `IntoDiagArg` is not implemented for `Hello`
+help: the nightly-only, unstable trait `IntoDiagArg` is not implemented for `Hello`
   --> $DIR/diagnostic-derive.rs:40:1
    |
 LL | struct Hello {}

diff --git a/tests/ui/abi/issues/issue-22565-rust-call.stderr b/tests/ui/abi/issues/issue-22565-rust-call.stderr
@@ -2,7 +2,7 @@ error[E0277]: functions with the "rust-call" ABI must take a single non-self tup
   --> $DIR/issue-22565-rust-call.rs:3:1
    |
 LL | extern "rust-call" fn b(_i: i32) {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Tuple` is not implemented for `i32`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `std::marker::Tuple` is not implemented for `i32`
 
 error: functions with the "rust-call" ABI must take a single non-self tuple argument
   --> $DIR/issue-22565-rust-call.rs:17:5
@@ -32,7 +32,7 @@ error[E0277]: functions with the "rust-call" ABI must take a single non-self tup
   --> $DIR/issue-22565-rust-call.rs:27:7
    |
 LL |     b(10);
-   |       ^^ the trait `std::marker::Tuple` is not implemented for `i32`
+   |       ^^ the nightly-only, unstable trait `std::marker::Tuple` is not implemented for `i32`
 
 error: functions with the "rust-call" ABI must take a single non-self tuple argument
   --> $DIR/issue-22565-rust-call.rs:29:5

diff --git a/tests/ui/async-await/coroutine-not-future.stderr b/tests/ui/async-await/coroutine-not-future.stderr
@@ -2,7 +2,7 @@ error[E0277]: the trait bound `impl Future<Output = ()>: Coroutine<_>` is not sa
   --> $DIR/coroutine-not-future.rs:36:21
    |
 LL |     takes_coroutine(async_fn());
-   |     --------------- ^^^^^^^^^^ the trait `Coroutine<_>` is not implemented for `impl Future<Output = ()>`
+   |     --------------- ^^^^^^^^^^ the nightly-only, unstable trait `Coroutine<_>` is not implemented for `impl Future<Output = ()>`
    |     |
    |     required by a bound introduced by this call
    |
@@ -16,7 +16,7 @@ error[E0277]: the trait bound `impl Future<Output = ()>: Coroutine<_>` is not sa
   --> $DIR/coroutine-not-future.rs:38:21
    |
 LL |     takes_coroutine(returns_async_block());
-   |     --------------- ^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine<_>` is not implemented for `impl Future<Output = ()>`
+   |     --------------- ^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `Coroutine<_>` is not implemented for `impl Future<Output = ()>`
    |     |
    |     required by a bound introduced by this call
    |
@@ -30,7 +30,7 @@ error[E0277]: the trait bound `{async block@$DIR/coroutine-not-future.rs:40:21:
   --> $DIR/coroutine-not-future.rs:40:21
    |
 LL |     takes_coroutine(async {});
-   |     --------------- ^^^^^^^^ the trait `Coroutine<_>` is not implemented for `{async block@$DIR/coroutine-not-future.rs:40:21: 40:26}`
+   |     --------------- ^^^^^^^^ the nightly-only, unstable trait `Coroutine<_>` is not implemented for `{async block@$DIR/coroutine-not-future.rs:40:21: 40:26}`
    |     |
    |     required by a bound introduced by this call
    |

diff --git a/tests/ui/async-await/issue-61076.rs b/tests/ui/async-await/issue-61076.rs
@@ -4,7 +4,7 @@ use core::future::Future;
 use core::pin::Pin;
 use core::task::{Context, Poll};
 
-struct T; //~ HELP the trait `Try` is not implemented for `T`
+struct T; //~ HELP the nightly-only, unstable trait `Try` is not implemented for `T`
 
 struct Tuple(i32);
 
@@ -41,7 +41,7 @@ async fn foo() -> Result<(), ()> {
 async fn bar() -> Result<(), ()> {
     foo()?; //~ ERROR the `?` operator can only be applied to values that implement `Try`
     //~^ NOTE the `?` operator cannot be applied to type `impl Future<Output = Result<(), ()>>`
-    //~| HELP the trait `Try` is not implemented for `impl Future<Output = Result<(), ()>>`
+    //~| HELP the nightly-only, unstable trait `Try` is not implemented for `impl Future<Output = Result<(), ()>>`
     //~| HELP consider `await`ing on the `Future`
     //~| NOTE in this expansion of desugaring of operator `?`
     //~| NOTE in this expansion of desugaring of operator `?`

diff --git a/tests/ui/async-await/issue-61076.stderr b/tests/ui/async-await/issue-61076.stderr
@@ -4,7 +4,7 @@ error[E0277]: the `?` operator can only be applied to values that implement `Try
 LL |     foo()?;
    |     ^^^^^^ the `?` operator cannot be applied to type `impl Future<Output = Result<(), ()>>`
    |
-   = help: the trait `Try` is not implemented for `impl Future<Output = Result<(), ()>>`
+   = help: the nightly-only, unstable trait `Try` is not implemented for `impl Future<Output = Result<(), ()>>`
 help: consider `await`ing on the `Future`
    |
 LL |     foo().await?;
@@ -16,7 +16,7 @@ error[E0277]: the `?` operator can only be applied to values that implement `Try
 LL |     t?;
    |     ^^ the `?` operator cannot be applied to type `T`
    |
-help: the trait `Try` is not implemented for `T`
+help: the nightly-only, unstable trait `Try` is not implemented for `T`
   --> $DIR/issue-61076.rs:7:1
    |
 LL | struct T;

diff --git a/tests/ui/async-await/issue-84841.stderr b/tests/ui/async-await/issue-84841.stderr
@@ -4,7 +4,7 @@ error[E0277]: the `?` operator can only be applied to values that implement `Try
 LL |     test()?;
    |     ^^^^^^^ the `?` operator cannot be applied to type `impl Future<Output = ()>`
    |
-   = help: the trait `Try` is not implemented for `impl Future<Output = ()>`
+   = help: the nightly-only, unstable trait `Try` is not implemented for `impl Future<Output = ()>`
 
 error[E0277]: the `?` operator can only be used in an async function that returns `Result` or `Option` (or another type that implements `FromResidual`)
   --> $DIR/issue-84841.rs:9:11

diff --git a/tests/ui/async-await/try-in-sync.stderr b/tests/ui/async-await/try-in-sync.stderr
@@ -4,7 +4,7 @@ error[E0277]: the `?` operator can only be applied to values that implement `Try
 LL |     foo()?;
    |     ^^^^^^ the `?` operator cannot be applied to type `impl Future<Output = Result<(), ()>>`
    |
-   = help: the trait `Try` is not implemented for `impl Future<Output = Result<(), ()>>`
+   = help: the nightly-only, unstable trait `Try` is not implemented for `impl Future<Output = Result<(), ()>>`
 note: this implements `Future` and its output type supports `?`, but the future cannot be awaited in a synchronous function
   --> $DIR/try-in-sync.rs:6:10
    |

diff --git a/tests/ui/const-generics/adt_const_params/const_param_ty_bad.stderr b/tests/ui/const-generics/adt_const_params/const_param_ty_bad.stderr
@@ -2,7 +2,7 @@ error[E0277]: `fn() {main}` can't be used as a const parameter type
   --> $DIR/const_param_ty_bad.rs:7:11
    |
 LL |     check(main);
-   |     ----- ^^^^ the trait `ConstParamTy_` is not implemented for fn item `fn() {main}`
+   |     ----- ^^^^ the nightly-only, unstable trait `ConstParamTy_` is not implemented for fn item `fn() {main}`
    |     |
    |     required by a bound introduced by this call
    |
@@ -24,7 +24,7 @@ LL |     check(|| {});
    |     |
    |     required by a bound introduced by this call
    |
-   = help: the trait `ConstParamTy_` is not implemented for closure `{closure@$DIR/const_param_ty_bad.rs:8:11: 8:13}`
+   = help: the nightly-only, unstable trait `ConstParamTy_` is not implemented for closure `{closure@$DIR/const_param_ty_bad.rs:8:11: 8:13}`
 note: required by a bound in `check`
   --> $DIR/const_param_ty_bad.rs:4:18
    |
@@ -40,7 +40,7 @@ error[E0277]: `fn()` can't be used as a const parameter type
   --> $DIR/const_param_ty_bad.rs:9:11
    |
 LL |     check(main as fn());
-   |     ----- ^^^^^^^^^^^^ the trait `ConstParamTy_` is not implemented for `fn()`
+   |     ----- ^^^^^^^^^^^^ the nightly-only, unstable trait `ConstParamTy_` is not implemented for `fn()`
    |     |
    |     required by a bound introduced by this call
    |
@@ -58,7 +58,7 @@ error[E0277]: `&mut ()` can't be used as a const parameter type
   --> $DIR/const_param_ty_bad.rs:10:11
    |
 LL |     check(&mut ());
-   |     ----- ^^^^^^^ the trait `ConstParamTy_` is not implemented for `&mut ()`
+   |     ----- ^^^^^^^ the nightly-only, unstable trait `ConstParamTy_` is not implemented for `&mut ()`
    |     |
    |     required by a bound introduced by this call
    |
@@ -78,7 +78,7 @@ error[E0277]: `*mut ()` can't be used as a const parameter type
   --> $DIR/const_param_ty_bad.rs:11:11
    |
 LL |     check(&mut () as *mut ());
-   |     ----- ^^^^^^^^^^^^^^^^^^ the trait `ConstParamTy_` is not implemented for `*mut ()`
+   |     ----- ^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `ConstParamTy_` is not implemented for `*mut ()`
    |     |
    |     required by a bound introduced by this call
    |
@@ -98,7 +98,7 @@ error[E0277]: `*const ()` can't be used as a const parameter type
   --> $DIR/const_param_ty_bad.rs:12:11
    |
 LL |     check(&() as *const ());
-   |     ----- ^^^^^^^^^^^^^^^^ the trait `ConstParamTy_` is not implemented for `*const ()`
+   |     ----- ^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `ConstParamTy_` is not implemented for `*const ()`
    |     |
    |     required by a bound introduced by this call
    |

diff --git a/tests/ui/const-generics/adt_const_params/const_param_ty_bad_empty_array.stderr b/tests/ui/const-generics/adt_const_params/const_param_ty_bad_empty_array.stderr
@@ -4,7 +4,7 @@ error[E0277]: `NotParam` can't be used as a const parameter type
 LL |     check::<[NotParam; 0]>();
    |             ^^^^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `ConstParamTy_` is not implemented for `NotParam`
+help: the nightly-only, unstable trait `ConstParamTy_` is not implemented for `NotParam`
   --> $DIR/const_param_ty_bad_empty_array.rs:5:1
    |
 LL | struct NotParam;

diff --git a/tests/ui/const-generics/adt_const_params/const_param_ty_generic_bounds_do_not_hold.stderr b/tests/ui/const-generics/adt_const_params/const_param_ty_generic_bounds_do_not_hold.stderr
@@ -4,7 +4,7 @@ error[E0277]: `NotParam` can't be used as a const parameter type
 LL |     check::<&NotParam>();
    |             ^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `ConstParamTy_` is not implemented for `NotParam`
+help: the nightly-only, unstable trait `ConstParamTy_` is not implemented for `NotParam`
   --> $DIR/const_param_ty_generic_bounds_do_not_hold.rs:5:1
    |
 LL | struct NotParam;
@@ -22,7 +22,7 @@ error[E0277]: `NotParam` can't be used as a const parameter type
 LL |     check::<[NotParam]>();
    |             ^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `ConstParamTy_` is not implemented for `NotParam`
+help: the nightly-only, unstable trait `ConstParamTy_` is not implemented for `NotParam`
   --> $DIR/const_param_ty_generic_bounds_do_not_hold.rs:5:1
    |
 LL | struct NotParam;
@@ -40,7 +40,7 @@ error[E0277]: `NotParam` can't be used as a const parameter type
 LL |     check::<[NotParam; 17]>();
    |             ^^^^^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `ConstParamTy_` is not implemented for `NotParam`
+help: the nightly-only, unstable trait `ConstParamTy_` is not implemented for `NotParam`
   --> $DIR/const_param_ty_generic_bounds_do_not_hold.rs:5:1
    |
 LL | struct NotParam;

diff --git a/tests/ui/const-generics/adt_const_params/const_param_ty_impl_no_structural_eq.stderr b/tests/ui/const-generics/adt_const_params/const_param_ty_impl_no_structural_eq.stderr
@@ -18,7 +18,7 @@ error[E0277]: the type `CantParam` does not `#[derive(PartialEq)]`
 LL | impl std::marker::ConstParamTy_ for CantParam {}
    |                                     ^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `StructuralPartialEq` is not implemented for `CantParam`
+help: the nightly-only, unstable trait `StructuralPartialEq` is not implemented for `CantParam`
   --> $DIR/const_param_ty_impl_no_structural_eq.rs:8:1
    |
 LL | struct CantParam(ImplementsConstParamTy);
@@ -46,7 +46,7 @@ error[E0277]: the type `CantParamDerive` does not `#[derive(PartialEq)]`
 LL | #[derive(std::marker::ConstParamTy)]
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
    |
-help: the trait `StructuralPartialEq` is not implemented for `CantParamDerive`
+help: the nightly-only, unstable trait `StructuralPartialEq` is not implemented for `CantParamDerive`
   --> $DIR/const_param_ty_impl_no_structural_eq.rs:17:1
    |
 LL | struct CantParamDerive(ImplementsConstParamTy);

diff --git a/tests/ui/coroutine/gen_block_is_coro.stderr b/tests/ui/coroutine/gen_block_is_coro.stderr
@@ -2,23 +2,23 @@ error[E0277]: the trait bound `{gen block@$DIR/gen_block_is_coro.rs:8:5: 8:8}: C
   --> $DIR/gen_block_is_coro.rs:7:13
    |
 LL | fn foo() -> impl Coroutine<Yield = u32, Return = ()> {
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:8:5: 8:8}`
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:8:5: 8:8}`
 LL |     gen { yield 42 }
    |     ---------------- return type was inferred to be `{gen block@$DIR/gen_block_is_coro.rs:8:5: 8:8}` here
 
 error[E0277]: the trait bound `{gen block@$DIR/gen_block_is_coro.rs:12:5: 12:8}: Coroutine` is not satisfied
   --> $DIR/gen_block_is_coro.rs:11:13
    |
 LL | fn bar() -> impl Coroutine<Yield = i64, Return = ()> {
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:12:5: 12:8}`
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:12:5: 12:8}`
 LL |     gen { yield 42 }
    |     ---------------- return type was inferred to be `{gen block@$DIR/gen_block_is_coro.rs:12:5: 12:8}` here
 
 error[E0277]: the trait bound `{gen block@$DIR/gen_block_is_coro.rs:16:5: 16:8}: Coroutine` is not satisfied
   --> $DIR/gen_block_is_coro.rs:15:13
    |
 LL | fn baz() -> impl Coroutine<Yield = i32, Return = ()> {
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:16:5: 16:8}`
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `Coroutine` is not implemented for `{gen block@$DIR/gen_block_is_coro.rs:16:5: 16:8}`
 LL |     gen { yield 42 }
    |     ---------------- return type was inferred to be `{gen block@$DIR/gen_block_is_coro.rs:16:5: 16:8}` here
 

diff --git a/tests/ui/error-codes/E0059.stderr b/tests/ui/error-codes/E0059.stderr
@@ -2,7 +2,7 @@ error[E0059]: type parameter to bare `Fn` trait must be a tuple
   --> $DIR/E0059.rs:3:11
    |
 LL | fn foo<F: Fn<i32>>(f: F) -> F::Output { f(3) }
-   |           ^^^^^^^ the trait `std::marker::Tuple` is not implemented for `i32`
+   |           ^^^^^^^ the nightly-only, unstable trait `std::marker::Tuple` is not implemented for `i32`
    |
 note: required by a bound in `Fn`
   --> $SRC_DIR/core/src/ops/function.rs:LL:COL
@@ -11,7 +11,7 @@ error[E0277]: `i32` is not a tuple
   --> $DIR/E0059.rs:3:41
    |
 LL | fn foo<F: Fn<i32>>(f: F) -> F::Output { f(3) }
-   |                                         ^^^^ the trait `std::marker::Tuple` is not implemented for `i32`
+   |                                         ^^^^ the nightly-only, unstable trait `std::marker::Tuple` is not implemented for `i32`
 
 error[E0059]: cannot use call notation; the first type parameter for the function trait is neither a tuple nor unit
   --> $DIR/E0059.rs:3:41

diff --git a/tests/ui/extern/extern-types-unsized.stderr b/tests/ui/extern/extern-types-unsized.stderr
@@ -65,7 +65,7 @@ error[E0277]: the size for values of type `A` cannot be known
 LL |     assert_sized::<Bar<A>>();
    |                    ^^^^^^ doesn't have a known size
    |
-   = help: the trait `MetaSized` is not implemented for `A`
+   = help: the nightly-only, unstable trait `MetaSized` is not implemented for `A`
 note: required by a bound in `Bar`
   --> $DIR/extern-types-unsized.rs:14:12
    |
@@ -100,7 +100,7 @@ error[E0277]: the size for values of type `A` cannot be known
 LL |     assert_sized::<Bar<Bar<A>>>();
    |                    ^^^^^^^^^^^ doesn't have a known size
    |
-   = help: the trait `MetaSized` is not implemented for `A`
+   = help: the nightly-only, unstable trait `MetaSized` is not implemented for `A`
 note: required by a bound in `Bar`
   --> $DIR/extern-types-unsized.rs:14:12
    |