Stabilize #[diagnostic::on_unknown]

compiler/rustc_attr_parsing/src/attributes/diagnostic/on_unknown.rs

@@ -14,10 +14,8 @@ impl AttributeParser for OnUnknownParser {
     const ATTRIBUTES: AcceptMapping<Self> = &[(
         &[sym::diagnostic, sym::on_unknown],
         template!(List: &[r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#]),
-        AttributeStability::Stable, // Unstable, stability checked manually below
+        AttributeStability::Stable,
         |this, cx, args| {
-            gate_diagnostic_attr!(diagnostic_on_unknown);
-
             let span = cx.attr_span;
             this.span = Some(span);
             let mode = Mode::DiagnosticOnUnknown;

compiler/rustc_feature/src/accepted.rs

@@ -191,6 +191,8 @@ 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)),
+    /// Allows giving unresolved imports a custom diagnostic message
+    (accepted, diagnostic_on_unknown, "CURRENT_RUSTC_VERSION", Some(152900)),
     /// Controls errors in trait implementations.
     (accepted, do_not_recommend, "1.85.0", Some(51992)),
     /// Allows `#[doc(alias = "...")]`.

compiler/rustc_feature/src/unstable.rs

@@ -497,8 +497,6 @@ declare_features! (
     (unstable, diagnostic_on_move, "1.96.0", Some(154181)),
     /// Allows giving custom types diagnostic messages on type errors
     (unstable, diagnostic_on_type_error, "1.98.0", Some(155382)),
-    /// Allows giving unresolved imports a custom diagnostic message
-    (unstable, diagnostic_on_unknown, "1.96.0", Some(152900)),
     /// Allows macros to customize macro argument matcher diagnostics.
     (unstable, diagnostic_on_unmatched_args, "1.97.0", Some(155642)),
     /// Used by macros to not show their bodies in error messages. No-op with `-Z macro-backtrace`.

compiler/rustc_resolve/src/diagnostics/impls.rs

@@ -4395,13 +4395,12 @@ impl OnUnknownData {
         r: &Resolver<'_, '_>,
         attrs: &[ast::Attribute],
     ) -> Option<OnUnknownData> {
-        if r.features.diagnostic_on_unknown()
-            && let Some(Attribute::Parsed(AttributeKind::OnUnknown { directive, .. })) =
-                AttributeParser::parse_limited_sym(
-                    r.tcx.sess,
-                    attrs,
-                    &[sym::diagnostic, sym::on_unknown],
-                )
+        if let Some(Attribute::Parsed(AttributeKind::OnUnknown { directive, .. })) =
+            AttributeParser::parse_limited_sym(
+                r.tcx.sess,
+                attrs,
+                &[sym::diagnostic, sym::on_unknown],
+            )
         {
             Some(Self { directive: directive? })
         } else {

compiler/rustc_span/src/lib.rs

@@ -17,10 +17,10 @@
 
 // tidy-alphabetical-start
 #![allow(internal_features)]
+#![cfg_attr(bootstrap, feature(diagnostic_on_unknown))]
 #![cfg_attr(target_arch = "loongarch64", feature(stdarch_loongarch))]
 #![feature(core_io_borrowed_buf)]
 #![feature(decl_macro)]
-#![feature(diagnostic_on_unknown)]
 #![feature(map_try_insert)]
 #![feature(negative_impls)]
 #![feature(read_buf)]

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

@@ -1,5 +1,4 @@
 #![crate_type = "lib"]
-#![feature(diagnostic_on_unknown)]
 
 #[diagnostic::on_unknown(message = "you silly, this module is empty")]
 pub mod empty {}

tests/ui/diagnostic_namespace/on_unknown/auxiliary/other_crate_level.rs

@@ -1,5 +1,4 @@
 #![feature(custom_inner_attributes)]
-#![feature(diagnostic_on_unknown)]
 #![crate_type = "lib"]
 
 #![diagnostic::on_unknown(message = "you silly, the crate `{This}` is empty")]

tests/ui/diagnostic_namespace/on_unknown/combined_use_and_module.rs

@@ -1,5 +1,4 @@
 #![crate_type = "lib"]
-#![feature(diagnostic_on_unknown)]
 
 #[diagnostic::on_unknown(
     message = "THIS MUST NEVER BE SHOWN",

tests/ui/diagnostic_namespace/on_unknown/combined_use_and_module.stderr

@@ -1,5 +1,5 @@
 error[E0432]: the message
-  --> $DIR/combined_use_and_module.rs:22:9
+  --> $DIR/combined_use_and_module.rs:21:9
    |
 LL | pub use constants::THREE;
    |         ^^^^^^^^^^^-----

tests/ui/diagnostic_namespace/on_unknown/crate_level.rs

@@ -3,7 +3,6 @@
 // See https://doc.rust-lang.org/nightly/reference/items/use-declarations.html#r-items.use.path.edition2018
 
 #![feature(custom_inner_attributes)]
-#![feature(diagnostic_on_unknown)]
 #![crate_type = "lib"]
 
 // Only applies to the root, not everything in the entire crate

tests/ui/diagnostic_namespace/on_unknown/crate_level.stderr

@@ -1,5 +1,5 @@
 error[E0432]: crate_level `crate_level_test`
-  --> $DIR/crate_level.rs:14:9
+  --> $DIR/crate_level.rs:13:9
    |
 LL | pub use crate::foo;
    |         ^^^^^^^---
@@ -9,29 +9,29 @@ LL | pub use crate::foo;
    = note: unresolved import `crate::foo`
 
 error[E0432]: unresolved import `bar`
-  --> $DIR/crate_level.rs:17:9
+  --> $DIR/crate_level.rs:16:9
    |
 LL | pub use ::bar;
    |         ^^---
    |           |
    |           no external crate `bar`
 
 error[E0432]: unresolved import `baz`
-  --> $DIR/crate_level.rs:20:9
+  --> $DIR/crate_level.rs:19:9
    |
 LL | pub use baz;
    |         ^^^ no external crate `baz`
 
 error[E0432]: unresolved import `crate::module::waz`
-  --> $DIR/crate_level.rs:23:9
+  --> $DIR/crate_level.rs:22:9
    |
 LL | pub use crate::module::waz;
    |         ^^^^^^^^^^^^^^^---
    |                        |
    |                        no `waz` in `module`
 
 error[E0432]: unresolved import `module::bluz`
-  --> $DIR/crate_level.rs:26:9
+  --> $DIR/crate_level.rs:25:9
    |
 LL | pub use module::bluz;
    |         ^^^^^^^^----

tests/ui/diagnostic_namespace/on_unknown/incorrect_format_string.rs

@@ -1,5 +1,3 @@
-#![feature(diagnostic_on_unknown)]
-
 #[diagnostic::on_unknown(message = "foo {}")]
 //~^ WARN: positional arguments are not permitted in diagnostic attributes
 use std::does_not_exist;