diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs
index 534458046945c..72e9215befb78 100644
--- a/compiler/rustc_feature/src/accepted.rs
+++ b/compiler/rustc_feature/src/accepted.rs
@@ -173,6 +173,8 @@ declare_features! (
     (accepted, destructuring_assignment, "1.59.0", Some(71126)),
     /// Allows using the `#[diagnostic]` attribute tool namespace
     (accepted, diagnostic_namespace, "1.78.0", Some(111996)),
+    /// Controls errors in trait implementations.
+    (accepted, do_not_recommend, "CURRENT_RUSTC_VERSION", Some(51992)),
     /// Allows `#[doc(alias = "...")]`.
     (accepted, doc_alias, "1.48.0", Some(50146)),
     /// Allows `..` in tuple (struct) patterns.
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index 477760a459757..151932edd4542 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -1190,10 +1190,9 @@ pub static BUILTIN_ATTRIBUTE_MAP: LazyLock<FxHashMap<Symbol, &BuiltinAttribute>>
         map
     });
 
-pub fn is_stable_diagnostic_attribute(sym: Symbol, features: &Features) -> bool {
+pub fn is_stable_diagnostic_attribute(sym: Symbol, _features: &Features) -> bool {
     match sym {
-        sym::on_unimplemented => true,
-        sym::do_not_recommend => features.do_not_recommend,
+        sym::on_unimplemented | sym::do_not_recommend => true,
         _ => false,
     }
 }
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 0606f2914c341..9e7dca81bbe72 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -469,8 +469,6 @@ declare_features! (
     (incomplete, deref_patterns, "1.79.0", Some(87121)),
     /// Allows deriving `SmartPointer` traits
     (unstable, derive_smart_pointer, "1.79.0", Some(123430)),
-    /// Controls errors in trait implementations.
-    (unstable, do_not_recommend, "1.67.0", Some(51992)),
     /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.
     (unstable, doc_auto_cfg, "1.58.0", Some(43781)),
     /// Allows `#[doc(cfg(...))]`.
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index 5e38fb5b6c51b..05336a60e9234 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -689,8 +689,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             && let [namespace, attribute, ..] = &*path.segments
             && namespace.ident.name == sym::diagnostic
             && !(attribute.ident.name == sym::on_unimplemented
-                || (attribute.ident.name == sym::do_not_recommend
-                    && self.tcx.features().do_not_recommend))
+                || attribute.ident.name == sym::do_not_recommend)
         {
             let distance =
                 edit_distance(attribute.ident.name.as_str(), sym::on_unimplemented.as_str(), 5);
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 168775667651d..b5e21d5f4cbe4 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -107,6 +107,7 @@
 //
 // Library features:
 // tidy-alphabetical-start
+#![cfg_attr(bootstrap, feature(do_not_recommend))]
 #![feature(array_ptr_get)]
 #![feature(asm_experimental_arch)]
 #![feature(const_align_of_val)]
@@ -145,7 +146,6 @@
 #![feature(const_ub_checks)]
 #![feature(const_unicode_case_lookup)]
 #![feature(coverage_attribute)]
-#![feature(do_not_recommend)]
 #![feature(internal_impls_macro)]
 #![feature(ip)]
 #![feature(is_ascii_octdigit)]
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.current.stderr
index 41f222e46a77c..2b26e89d6c8d6 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.current.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.current.stderr
@@ -1,5 +1,5 @@
 error[E0277]: the trait bound `&str: AsExpression<Integer>` is not satisfied
-  --> $DIR/as_expression.rs:57:15
+  --> $DIR/as_expression.rs:55:15
    |
 LL |     SelectInt.check("bar");
    |               ^^^^^ the trait `AsExpression<Integer>` is not implemented for `&str`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.next.stderr
index 8c01b61191e60..196dfa3cb9ff7 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.next.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.next.stderr
@@ -1,5 +1,5 @@
 error[E0277]: the trait bound `&str: AsExpression<<SelectInt as Expression>::SqlType>` is not satisfied
-  --> $DIR/as_expression.rs:57:21
+  --> $DIR/as_expression.rs:55:21
    |
 LL |     SelectInt.check("bar");
    |               ----- ^^^^^ the trait `AsExpression<<SelectInt as Expression>::SqlType>` is not implemented for `&str`
@@ -8,7 +8,7 @@ LL |     SelectInt.check("bar");
    |
    = help: the trait `AsExpression<Text>` is implemented for `&str`
 note: required by a bound in `Foo::check`
-  --> $DIR/as_expression.rs:48:12
+  --> $DIR/as_expression.rs:46:12
    |
 LL |     fn check<T>(&self, _: T) -> <T as AsExpression<<Self as Expression>::SqlType>>::Expression
    |        ----- required by a bound in this associated function
@@ -17,7 +17,7 @@ LL |         T: AsExpression<Self::SqlType>,
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Foo::check`
 
 error[E0277]: the trait bound `&str: AsExpression<Integer>` is not satisfied
-  --> $DIR/as_expression.rs:57:15
+  --> $DIR/as_expression.rs:55:15
    |
 LL |     SelectInt.check("bar");
    |               ^^^^^ the trait `AsExpression<Integer>` is not implemented for `&str`
@@ -26,7 +26,7 @@ LL |     SelectInt.check("bar");
    = help: for that trait implementation, expected `Text`, found `Integer`
 
 error[E0271]: type mismatch resolving `<SelectInt as Expression>::SqlType == Text`
-  --> $DIR/as_expression.rs:57:5
+  --> $DIR/as_expression.rs:55:5
    |
 LL |     SelectInt.check("bar");
    |     ^^^^^^^^^^^^^^^^^^^^^^ expected `Text`, found `Integer`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.rs b/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.rs
index 37b4429f694cf..583b3c4675a87 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.rs
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/as_expression.rs
@@ -2,8 +2,6 @@
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 
-#![feature(do_not_recommend)]
-
 pub trait Expression {
     type SqlType;
 }
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.current.stderr
deleted file mode 100644
index 1cd148186f1ea..0000000000000
--- a/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.current.stderr
+++ /dev/null
@@ -1,21 +0,0 @@
-error[E0277]: the trait bound `(): Foo` is not satisfied
-  --> $DIR/do_not_apply_attribute_without_feature_flag.rs:22:11
-   |
-LL |     check(());
-   |     ----- ^^ the trait `Foo` is not implemented for `()`
-   |     |
-   |     required by a bound introduced by this call
-   |
-   = help: the following other types implement trait `Foo`:
-             (A, B)
-             (A, B, C)
-             (A,)
-note: required by a bound in `check`
-  --> $DIR/do_not_apply_attribute_without_feature_flag.rs:19:18
-   |
-LL | fn check(a: impl Foo) {}
-   |                  ^^^ required by this bound in `check`
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.next.stderr
deleted file mode 100644
index 1cd148186f1ea..0000000000000
--- a/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.next.stderr
+++ /dev/null
@@ -1,21 +0,0 @@
-error[E0277]: the trait bound `(): Foo` is not satisfied
-  --> $DIR/do_not_apply_attribute_without_feature_flag.rs:22:11
-   |
-LL |     check(());
-   |     ----- ^^ the trait `Foo` is not implemented for `()`
-   |     |
-   |     required by a bound introduced by this call
-   |
-   = help: the following other types implement trait `Foo`:
-             (A, B)
-             (A, B, C)
-             (A,)
-note: required by a bound in `check`
-  --> $DIR/do_not_apply_attribute_without_feature_flag.rs:19:18
-   |
-LL | fn check(a: impl Foo) {}
-   |                  ^^^ required by this bound in `check`
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.rs b/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.rs
deleted file mode 100644
index 9c25069bc7d5b..0000000000000
--- a/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.rs
+++ /dev/null
@@ -1,24 +0,0 @@
-//@ revisions: current next
-//@ ignore-compare-mode-next-solver (explicit revisions)
-//@[next] compile-flags: -Znext-solver
-#![allow(unknown_or_malformed_diagnostic_attributes)]
-
-trait Foo {}
-
-#[diagnostic::do_not_recommend]
-impl<A> Foo for (A,) {}
-
-#[diagnostic::do_not_recommend]
-impl<A, B> Foo for (A, B) {}
-
-#[diagnostic::do_not_recommend]
-impl<A, B, C> Foo for (A, B, C) {}
-
-impl Foo for i32 {}
-
-fn check(a: impl Foo) {}
-
-fn main() {
-    check(());
-    //~^ ERROR the trait bound `(): Foo` is not satisfied
-}
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.current.stderr
index 3d004ca559e89..47597a5d405e4 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.current.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.current.stderr
@@ -1,5 +1,5 @@
 warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
-  --> $DIR/does_not_acccept_args.rs:12:1
+  --> $DIR/does_not_acccept_args.rs:10:1
    |
 LL | #[diagnostic::do_not_recommend(not_accepted)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -7,13 +7,13 @@ LL | #[diagnostic::do_not_recommend(not_accepted)]
    = note: `#[warn(unknown_or_malformed_diagnostic_attributes)]` on by default
 
 warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
-  --> $DIR/does_not_acccept_args.rs:16:1
+  --> $DIR/does_not_acccept_args.rs:14:1
    |
 LL | #[diagnostic::do_not_recommend(not_accepted = "foo")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
-  --> $DIR/does_not_acccept_args.rs:20:1
+  --> $DIR/does_not_acccept_args.rs:18:1
    |
 LL | #[diagnostic::do_not_recommend(not_accepted(42))]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.next.stderr
index 3d004ca559e89..47597a5d405e4 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.next.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.next.stderr
@@ -1,5 +1,5 @@
 warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
-  --> $DIR/does_not_acccept_args.rs:12:1
+  --> $DIR/does_not_acccept_args.rs:10:1
    |
 LL | #[diagnostic::do_not_recommend(not_accepted)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -7,13 +7,13 @@ LL | #[diagnostic::do_not_recommend(not_accepted)]
    = note: `#[warn(unknown_or_malformed_diagnostic_attributes)]` on by default
 
 warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
-  --> $DIR/does_not_acccept_args.rs:16:1
+  --> $DIR/does_not_acccept_args.rs:14:1
    |
 LL | #[diagnostic::do_not_recommend(not_accepted = "foo")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
-  --> $DIR/does_not_acccept_args.rs:20:1
+  --> $DIR/does_not_acccept_args.rs:18:1
    |
 LL | #[diagnostic::do_not_recommend(not_accepted(42))]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.rs b/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.rs
index f3295546f34b7..eeff5e2e6e8fc 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.rs
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.rs
@@ -3,8 +3,6 @@
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 
-#![feature(do_not_recommend)]
-
 trait Foo {}
 trait Bar {}
 trait Baz {}
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/feature-gate-do_not_recommend.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/feature-gate-do_not_recommend.current.stderr
deleted file mode 100644
index d1deaa6a00626..0000000000000
--- a/tests/ui/diagnostic_namespace/do_not_recommend/feature-gate-do_not_recommend.current.stderr
+++ /dev/null
@@ -1,15 +0,0 @@
-error[E0277]: the trait bound `u8: Bar` is not satisfied
-  --> $DIR/feature-gate-do_not_recommend.rs:18:11
-   |
-LL |     stuff(1u8);
-   |           ^^^ the trait `Bar` is not implemented for `u8`
-   |
-note: required by a bound in `stuff`
-  --> $DIR/feature-gate-do_not_recommend.rs:15:13
-   |
-LL | fn stuff<T: Bar>(_: T) {}
-   |             ^^^ required by this bound in `stuff`
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/feature-gate-do_not_recommend.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/feature-gate-do_not_recommend.next.stderr
deleted file mode 100644
index 5bfcc60edc555..0000000000000
--- a/tests/ui/diagnostic_namespace/do_not_recommend/feature-gate-do_not_recommend.next.stderr
+++ /dev/null
@@ -1,17 +0,0 @@
-error[E0277]: the trait bound `u8: Bar` is not satisfied
-  --> $DIR/feature-gate-do_not_recommend.rs:18:11
-   |
-LL |     stuff(1u8);
-   |     ----- ^^^ the trait `Bar` is not implemented for `u8`
-   |     |
-   |     required by a bound introduced by this call
-   |
-note: required by a bound in `stuff`
-  --> $DIR/feature-gate-do_not_recommend.rs:15:13
-   |
-LL | fn stuff<T: Bar>(_: T) {}
-   |             ^^^ required by this bound in `stuff`
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/feature-gate-do_not_recommend.rs b/tests/ui/diagnostic_namespace/do_not_recommend/feature-gate-do_not_recommend.rs
deleted file mode 100644
index 4adce112f15ec..0000000000000
--- a/tests/ui/diagnostic_namespace/do_not_recommend/feature-gate-do_not_recommend.rs
+++ /dev/null
@@ -1,20 +0,0 @@
-//@ revisions: current next
-//@ ignore-compare-mode-next-solver (explicit revisions)
-//@[next] compile-flags: -Znext-solver
-#![feature(do_not_recommend)]
-
-pub trait Foo {}
-
-impl Foo for i32 {}
-
-pub trait Bar {}
-
-#[diagnostic::do_not_recommend]
-impl<T: Foo> Bar for T {}
-
-fn stuff<T: Bar>(_: T) {}
-
-fn main() {
-    stuff(1u8);
-    //~^ the trait bound `u8: Bar` is not satisfied
-}
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.current.stderr
index 84ab0827ab689..0b0dac32b39f5 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.current.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.current.stderr
@@ -1,5 +1,5 @@
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:7:1
+  --> $DIR/incorrect-locations.rs:6:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -7,43 +7,43 @@ LL | #[diagnostic::do_not_recommend]
    = note: `#[warn(unknown_or_malformed_diagnostic_attributes)]` on by default
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:11:1
+  --> $DIR/incorrect-locations.rs:10:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:15:1
+  --> $DIR/incorrect-locations.rs:14:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:19:1
+  --> $DIR/incorrect-locations.rs:18:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:23:1
+  --> $DIR/incorrect-locations.rs:22:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:27:1
+  --> $DIR/incorrect-locations.rs:26:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:31:1
+  --> $DIR/incorrect-locations.rs:30:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:35:1
+  --> $DIR/incorrect-locations.rs:34:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.next.stderr
index 84ab0827ab689..0b0dac32b39f5 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.next.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.next.stderr
@@ -1,5 +1,5 @@
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:7:1
+  --> $DIR/incorrect-locations.rs:6:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -7,43 +7,43 @@ LL | #[diagnostic::do_not_recommend]
    = note: `#[warn(unknown_or_malformed_diagnostic_attributes)]` on by default
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:11:1
+  --> $DIR/incorrect-locations.rs:10:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:15:1
+  --> $DIR/incorrect-locations.rs:14:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:19:1
+  --> $DIR/incorrect-locations.rs:18:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:23:1
+  --> $DIR/incorrect-locations.rs:22:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:27:1
+  --> $DIR/incorrect-locations.rs:26:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:31:1
+  --> $DIR/incorrect-locations.rs:30:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
-  --> $DIR/incorrect-locations.rs:35:1
+  --> $DIR/incorrect-locations.rs:34:1
    |
 LL | #[diagnostic::do_not_recommend]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.rs b/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.rs
index daacf55ea7921..014be580f61fb 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.rs
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/incorrect-locations.rs
@@ -2,7 +2,6 @@
 //@ revisions: current next
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
-#![feature(do_not_recommend)]
 
 #[diagnostic::do_not_recommend]
 //~^WARN `#[diagnostic::do_not_recommend]` can only be placed
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/nested.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/nested.current.stderr
index 2e08a6793602f..b14c68d689766 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/nested.current.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/nested.current.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `(): Root` is not satisfied
-  --> $DIR/nested.rs:23:18
+  --> $DIR/nested.rs:21:18
    |
 LL |     needs_root::<()>();
    |                  ^^ the trait `Root` is not implemented for `()`
    |
 note: required by a bound in `needs_root`
-  --> $DIR/nested.rs:20:18
+  --> $DIR/nested.rs:18:18
    |
 LL | fn needs_root<T: Root>() {}
    |                  ^^^^ required by this bound in `needs_root`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/nested.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/nested.next.stderr
index 2e08a6793602f..b14c68d689766 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/nested.next.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/nested.next.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `(): Root` is not satisfied
-  --> $DIR/nested.rs:23:18
+  --> $DIR/nested.rs:21:18
    |
 LL |     needs_root::<()>();
    |                  ^^ the trait `Root` is not implemented for `()`
    |
 note: required by a bound in `needs_root`
-  --> $DIR/nested.rs:20:18
+  --> $DIR/nested.rs:18:18
    |
 LL | fn needs_root<T: Root>() {}
    |                  ^^^^ required by this bound in `needs_root`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/nested.rs b/tests/ui/diagnostic_namespace/do_not_recommend/nested.rs
index d499cff9f56eb..6534157d1fb2e 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/nested.rs
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/nested.rs
@@ -2,8 +2,6 @@
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 
-#![feature(do_not_recommend)]
-
 trait Root {}
 trait DontRecommend {}
 trait Other {}
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/simple.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/simple.current.stderr
index 729cb5694e216..884b13c17b802 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/simple.current.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/simple.current.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `*mut (): Foo` is not satisfied
-  --> $DIR/simple.rs:17:17
+  --> $DIR/simple.rs:15:17
    |
 LL |     needs_foo::<*mut ()>();
    |                 ^^^^^^^ the trait `Foo` is not implemented for `*mut ()`
    |
 note: required by a bound in `needs_foo`
-  --> $DIR/simple.rs:12:17
+  --> $DIR/simple.rs:10:17
    |
 LL | fn needs_foo<T: Foo>() {}
    |                 ^^^ required by this bound in `needs_foo`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/simple.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/simple.next.stderr
index 729cb5694e216..884b13c17b802 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/simple.next.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/simple.next.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `*mut (): Foo` is not satisfied
-  --> $DIR/simple.rs:17:17
+  --> $DIR/simple.rs:15:17
    |
 LL |     needs_foo::<*mut ()>();
    |                 ^^^^^^^ the trait `Foo` is not implemented for `*mut ()`
    |
 note: required by a bound in `needs_foo`
-  --> $DIR/simple.rs:12:17
+  --> $DIR/simple.rs:10:17
    |
 LL | fn needs_foo<T: Foo>() {}
    |                 ^^^ required by this bound in `needs_foo`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/simple.rs b/tests/ui/diagnostic_namespace/do_not_recommend/simple.rs
index 780649b009c63..6bca2b724d240 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/simple.rs
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/simple.rs
@@ -2,8 +2,6 @@
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 
-#![feature(do_not_recommend)]
-
 trait Foo {}
 
 #[diagnostic::do_not_recommend]
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/stacked.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/stacked.current.stderr
index 41a10a61e1dfd..d86058063955e 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/stacked.current.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/stacked.current.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `(): Root` is not satisfied
-  --> $DIR/stacked.rs:19:18
+  --> $DIR/stacked.rs:17:18
    |
 LL |     needs_root::<()>();
    |                  ^^ the trait `Root` is not implemented for `()`
    |
 note: required by a bound in `needs_root`
-  --> $DIR/stacked.rs:16:18
+  --> $DIR/stacked.rs:14:18
    |
 LL | fn needs_root<T: Root>() {}
    |                  ^^^^ required by this bound in `needs_root`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/stacked.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/stacked.next.stderr
index 41a10a61e1dfd..d86058063955e 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/stacked.next.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/stacked.next.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `(): Root` is not satisfied
-  --> $DIR/stacked.rs:19:18
+  --> $DIR/stacked.rs:17:18
    |
 LL |     needs_root::<()>();
    |                  ^^ the trait `Root` is not implemented for `()`
    |
 note: required by a bound in `needs_root`
-  --> $DIR/stacked.rs:16:18
+  --> $DIR/stacked.rs:14:18
    |
 LL | fn needs_root<T: Root>() {}
    |                  ^^^^ required by this bound in `needs_root`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/stacked.rs b/tests/ui/diagnostic_namespace/do_not_recommend/stacked.rs
index fc355bdc4e204..842e04b9d9017 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/stacked.rs
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/stacked.rs
@@ -2,8 +2,6 @@
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 
-#![feature(do_not_recommend)]
-
 trait Root {}
 trait DontRecommend {}
 trait Other {}
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.current.stderr
index 629fc59361dd2..92fa4017af319 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.current.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.current.stderr
@@ -1,5 +1,5 @@
 error[E0277]: the trait bound `(): Foo` is not satisfied
-  --> $DIR/supress_suggestions_in_help.rs:23:11
+  --> $DIR/supress_suggestions_in_help.rs:21:11
    |
 LL |     check(());
    |     ----- ^^ the trait `Foo` is not implemented for `()`
@@ -8,7 +8,7 @@ LL |     check(());
    |
    = help: the trait `Foo` is implemented for `i32`
 note: required by a bound in `check`
-  --> $DIR/supress_suggestions_in_help.rs:20:18
+  --> $DIR/supress_suggestions_in_help.rs:18:18
    |
 LL | fn check(a: impl Foo) {}
    |                  ^^^ required by this bound in `check`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.next.stderr
index 629fc59361dd2..92fa4017af319 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.next.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.next.stderr
@@ -1,5 +1,5 @@
 error[E0277]: the trait bound `(): Foo` is not satisfied
-  --> $DIR/supress_suggestions_in_help.rs:23:11
+  --> $DIR/supress_suggestions_in_help.rs:21:11
    |
 LL |     check(());
    |     ----- ^^ the trait `Foo` is not implemented for `()`
@@ -8,7 +8,7 @@ LL |     check(());
    |
    = help: the trait `Foo` is implemented for `i32`
 note: required by a bound in `check`
-  --> $DIR/supress_suggestions_in_help.rs:20:18
+  --> $DIR/supress_suggestions_in_help.rs:18:18
    |
 LL | fn check(a: impl Foo) {}
    |                  ^^^ required by this bound in `check`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.rs b/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.rs
index ef6f255c3518b..2c7c151612303 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.rs
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.rs
@@ -2,8 +2,6 @@
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 
-#![feature(do_not_recommend)]
-
 trait Foo {}
 
 #[diagnostic::do_not_recommend]
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.current.stderr
index bcede8a255f23..b53febbb71ab8 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.current.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.current.stderr
@@ -1,11 +1,11 @@
 error[E0277]: Very important message!
-  --> $DIR/type_mismatch.rs:25:14
+  --> $DIR/type_mismatch.rs:23:14
    |
 LL |     verify::<u8>();
    |              ^^ the trait `TheImportantOne` is not implemented for `u8`
    |
 note: required by a bound in `verify`
-  --> $DIR/type_mismatch.rs:22:14
+  --> $DIR/type_mismatch.rs:20:14
    |
 LL | fn verify<T: TheImportantOne>() {}
    |              ^^^^^^^^^^^^^^^ required by this bound in `verify`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.next.stderr
index bcede8a255f23..b53febbb71ab8 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.next.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.next.stderr
@@ -1,11 +1,11 @@
 error[E0277]: Very important message!
-  --> $DIR/type_mismatch.rs:25:14
+  --> $DIR/type_mismatch.rs:23:14
    |
 LL |     verify::<u8>();
    |              ^^ the trait `TheImportantOne` is not implemented for `u8`
    |
 note: required by a bound in `verify`
-  --> $DIR/type_mismatch.rs:22:14
+  --> $DIR/type_mismatch.rs:20:14
    |
 LL | fn verify<T: TheImportantOne>() {}
    |              ^^^^^^^^^^^^^^^ required by this bound in `verify`
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.rs b/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.rs
index d6721ccc848f8..7f30fdb06c75a 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.rs
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/type_mismatch.rs
@@ -2,8 +2,6 @@
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 
-#![feature(do_not_recommend)]
-
 #[diagnostic::on_unimplemented(message = "Very important message!")]
 trait TheImportantOne {}
 
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/unstable-feature.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/unstable-feature.current.stderr
deleted file mode 100644
index fdea9eacae142..0000000000000
--- a/tests/ui/diagnostic_namespace/do_not_recommend/unstable-feature.current.stderr
+++ /dev/null
@@ -1,14 +0,0 @@
-error: unknown diagnostic attribute
-  --> $DIR/unstable-feature.rs:7:15
-   |
-LL | #[diagnostic::do_not_recommend]
-   |               ^^^^^^^^^^^^^^^^
-   |
-note: the lint level is defined here
-  --> $DIR/unstable-feature.rs:4:9
-   |
-LL | #![deny(unknown_or_malformed_diagnostic_attributes)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 1 previous error
-
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/unstable-feature.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/unstable-feature.next.stderr
deleted file mode 100644
index fdea9eacae142..0000000000000
--- a/tests/ui/diagnostic_namespace/do_not_recommend/unstable-feature.next.stderr
+++ /dev/null
@@ -1,14 +0,0 @@
-error: unknown diagnostic attribute
-  --> $DIR/unstable-feature.rs:7:15
-   |
-LL | #[diagnostic::do_not_recommend]
-   |               ^^^^^^^^^^^^^^^^
-   |
-note: the lint level is defined here
-  --> $DIR/unstable-feature.rs:4:9
-   |
-LL | #![deny(unknown_or_malformed_diagnostic_attributes)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 1 previous error
-
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/unstable-feature.rs b/tests/ui/diagnostic_namespace/do_not_recommend/unstable-feature.rs
deleted file mode 100644
index 7a67f67b67f23..0000000000000
--- a/tests/ui/diagnostic_namespace/do_not_recommend/unstable-feature.rs
+++ /dev/null
@@ -1,11 +0,0 @@
-//@ revisions: current next
-//@ ignore-compare-mode-next-solver (explicit revisions)
-//@[next] compile-flags: -Znext-solver
-#![deny(unknown_or_malformed_diagnostic_attributes)]
-trait Foo {}
-
-#[diagnostic::do_not_recommend]
-//~^ ERROR unknown diagnostic attribute [unknown_or_malformed_diagnostic_attributes]
-impl Foo for i32 {}
-
-fn main() {}
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.current.stderr
index c2874cf45945c..a8429ff60f83a 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.current.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.current.stderr
@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/with_lifetime.rs:19:5
+  --> $DIR/with_lifetime.rs:17:5
    |
 LL | fn foo<'a>(a: &'a ()) {
    |        -- lifetime `'a` defined here
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.next.stderr
index c2874cf45945c..a8429ff60f83a 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.next.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.next.stderr
@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/with_lifetime.rs:19:5
+  --> $DIR/with_lifetime.rs:17:5
    |
 LL | fn foo<'a>(a: &'a ()) {
    |        -- lifetime `'a` defined here
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.rs b/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.rs
index 9aaf7f33ecdcc..6a67d83d5fe4d 100644
--- a/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.rs
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/with_lifetime.rs
@@ -2,8 +2,6 @@
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 
-#![feature(do_not_recommend)]
-
 trait Root {}
 trait DontRecommend {}