privacy: Feature gate new type privacy lints

compiler/rustc_feature/src/active.rs

@@ -539,6 +539,8 @@ declare_features! (
     /// Allows creation of instances of a struct by moving fields that have
     /// not changed from prior instances of the same struct (RFC #2528)
     (active, type_changing_struct_update, "1.58.0", Some(86555), None),
+    /// Allows using type privacy lints (`private_interfaces`, `private_bounds`, `unnameable_types`).
+    (active, type_privacy_lints, "CURRENT_RUSTC_VERSION", Some(48054), None),
     /// Enables rustc to generate code that instructs libstd to NOT ignore SIGPIPE.
     (active, unix_sigpipe, "1.65.0", Some(97889), None),
     /// Allows unsized fn parameters.

compiler/rustc_lint_defs/src/builtin.rs

@@ -4263,6 +4263,7 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust,compile_fail
+    /// # #![feature(type_privacy_lints)]
     /// # #![allow(unused)]
     /// # #![allow(private_in_public)]
     /// #![deny(private_interfaces)]
@@ -4287,6 +4288,7 @@ declare_lint! {
     pub PRIVATE_INTERFACES,
     Allow,
     "private type in primary interface of an item",
+    @feature_gate = sym::type_privacy_lints;
 }
 
 declare_lint! {
@@ -4297,6 +4299,7 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust,compile_fail
+    /// # #![feature(type_privacy_lints)]
     /// # #![allow(private_in_public)]
     /// # #![allow(unused)]
     /// #![deny(private_bounds)]
@@ -4316,7 +4319,8 @@ declare_lint! {
     /// the item actually provides.
     pub PRIVATE_BOUNDS,
     Allow,
-    "private type in secondary interface of an item"
+    "private type in secondary interface of an item",
+    @feature_gate = sym::type_privacy_lints;
 }
 
 declare_lint! {
@@ -4326,6 +4330,7 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust,compile_fail
+    /// # #![feature(type_privacy_lints)]
     /// # #![allow(unused)]
     /// #![deny(unnameable_types)]
     /// mod m {
@@ -4344,5 +4349,6 @@ declare_lint! {
     /// you can name the type `T` as well, this lint attempts to enforce this rule.
     pub UNNAMEABLE_TYPES,
     Allow,
-    "effective visibility of a type is larger than the area in which it can be named"
+    "effective visibility of a type is larger than the area in which it can be named",
+    @feature_gate = sym::type_privacy_lints;
 }

compiler/rustc_span/src/symbol.rs

@@ -1555,6 +1555,7 @@ symbols! {
         type_length_limit,
         type_macros,
         type_name,
+        type_privacy_lints,
         u128,
         u16,
         u32,