Stabilize the #[diagnostic] namespace and #[diagnostic::on_unimplemented] attribute

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -203,14 +203,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 );
             }
         }
-        if !attr.is_doc_comment()
-            && let [seg, _] = attr.get_normal_item().path.segments.as_slice()
-            && seg.ident.name == sym::diagnostic
-            && !self.features.diagnostic_namespace
-        {
-            let msg = "`#[diagnostic]` attribute name space is experimental";
-            gate!(self, diagnostic_namespace, seg.ident.span, msg);
-        }
 
         // Emit errors for non-staged-api crates.
         if !self.features.staged_api {

compiler/rustc_feature/src/accepted.rs

@@ -146,6 +146,8 @@ declare_features! (
     (accepted, derive_default_enum, "1.62.0", Some(86985)),
     /// Allows the use of destructuring assignments.
     (accepted, destructuring_assignment, "1.59.0", Some(71126)),
+    /// Allows using the `#[diagnostic]` attribute tool namespace
+    (accepted, diagnostic_namespace, "CURRENT_RUSTC_VERSION", Some(111996)),
     /// Allows `#[doc(alias = "...")]`.
     (accepted, doc_alias, "1.48.0", Some(50146)),
     /// Allows `..` in tuple (struct) patterns.

compiler/rustc_feature/src/unstable.rs

@@ -434,8 +434,6 @@ declare_features! (
     (unstable, deprecated_safe, "1.61.0", Some(94978)),
     /// Allows having using `suggestion` in the `#[deprecated]` attribute.
     (unstable, deprecated_suggestion, "1.61.0", Some(94785)),
-    /// Allows using the `#[diagnostic]` attribute tool namespace
-    (unstable, diagnostic_namespace, "1.73.0", Some(111996)),
     /// Controls errors in trait implementations.
     (unstable, do_not_recommend, "1.67.0", Some(51992)),
     /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.

library/core/src/lib.rs

@@ -202,6 +202,7 @@
 //
 // Language features:
 // tidy-alphabetical-start
+#![cfg_attr(bootstrap, feature(diagnostic_namespace))]
 #![cfg_attr(bootstrap, feature(platform_intrinsics))]
 #![feature(abi_unadjusted)]
 #![feature(adt_const_params)]
@@ -223,7 +224,6 @@
 #![feature(const_trait_impl)]
 #![feature(decl_macro)]
 #![feature(deprecated_suggestion)]
-#![feature(diagnostic_namespace)]
 #![feature(doc_cfg)]
 #![feature(doc_cfg_hide)]
 #![feature(doc_notable_trait)]

tests/ui/diagnostic_namespace/existing_proc_macros.rs

@@ -1,4 +1,3 @@
-#![feature(diagnostic_namespace)]
 //@ check-pass
 //@ aux-build:proc-macro-helper.rs
 

tests/ui/diagnostic_namespace/non_existing_attributes_accepted.rs

@@ -1,4 +1,3 @@
-#![feature(diagnostic_namespace)]
 //@ check-pass
 #[diagnostic::non_existing_attribute]
 //~^WARN unknown diagnostic attribute

tests/ui/diagnostic_namespace/non_existing_attributes_accepted.stderr

@@ -1,13 +1,13 @@
 warning: unknown diagnostic attribute
-  --> $DIR/non_existing_attributes_accepted.rs:3:15
+  --> $DIR/non_existing_attributes_accepted.rs:2:15
    |
 LL | #[diagnostic::non_existing_attribute]
    |               ^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `#[warn(unknown_or_malformed_diagnostic_attributes)]` on by default
 
 warning: unknown diagnostic attribute
-  --> $DIR/non_existing_attributes_accepted.rs:8:15
+  --> $DIR/non_existing_attributes_accepted.rs:7:15
    |
 LL | #[diagnostic::non_existing_attribute(with_option = "foo")]
    |               ^^^^^^^^^^^^^^^^^^^^^^

tests/ui/diagnostic_namespace/on_unimplemented/auxiliary/other.rs

@@ -1,5 +1,3 @@
-#![feature(diagnostic_namespace)]
-
 #[diagnostic::on_unimplemented(
     message = "Message",
     note = "Note",

tests/ui/diagnostic_namespace/on_unimplemented/do_not_accept_options_of_the_internal_rustc_attribute.rs

@@ -1,5 +1,3 @@
-#![feature(diagnostic_namespace)]
-
 #[diagnostic::on_unimplemented(
     on(_Self = "&str"),
     //~^WARN malformed `on_unimplemented` attribute