Remove deprecated_safe and its corresponding feature gate

compiler/rustc_feature/src/builtin_attrs.rs

@@ -862,13 +862,6 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         register_tool, CrateLevel, template!(List: &["tool1, tool2, ..."]), DuplicatesOk,
         EncodeCrossCrate::No, experimental!(register_tool),
     ),
-
-    // lang-team MCP 147
-    gated!(
-        deprecated_safe, Normal, template!(List: &[r#"since = "version", note = "...""#]), ErrorFollowing,
-        EncodeCrossCrate::Yes, experimental!(deprecated_safe),
-    ),
-
     // `#[cfi_encoding = ""]`
     gated!(
         cfi_encoding, Normal, template!(NameValueStr: "encoding"), ErrorPreceding,

compiler/rustc_feature/src/removed.rs

@@ -102,6 +102,8 @@ declare_features! (
     /// Allows default type parameters to influence type inference.
     (removed, default_type_parameter_fallback, "1.82.0", Some(27336),
      Some("never properly implemented; requires significant design work"), 127655),
+    /// Allows using `#[deprecated_safe]` to deprecate the safeness of a function or trait
+    (removed, deprecated_safe, "CURRENT_RUSTC_VERSION", Some(94978), Some("never properly implemented, in the way of attribute refactor"), 152554),
     /// Allows deriving traits as per `SmartPointer` specification
     (removed, derive_smart_pointer, "1.84.0", Some(123430), Some("replaced by `CoercePointee`"), 131284),
     /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.

compiler/rustc_feature/src/unstable.rs

@@ -454,8 +454,6 @@ declare_features! (
     /// Allows the use of default values on struct definitions and the construction of struct
     /// literals with the functional update syntax without a base.
     (unstable, default_field_values, "1.85.0", Some(132162)),
-    /// Allows using `#[deprecated_safe]` to deprecate the safeness of a function or trait
-    (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 deref patterns.

compiler/rustc_passes/src/check_attr.rs

@@ -391,8 +391,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             | sym::warn
                             | sym::deny
                             | sym::forbid
-                            // need to be fixed
-                            | sym::deprecated_safe // FIXME(deprecated_safe)
                             // internal
                             | sym::prelude_import
                             | sym::panic_handler