Soft-destabilize RustcEncodable/RustcDecodable

library/core/src/macros/mod.rs

@@ -1726,20 +1726,28 @@ macro_rules! trace_macros {
         builtin # deref($pat)
     }
 
-    /// Unstable implementation detail of the `rustc` compiler, do not use.
+    /// Derive macro for `rustc-serialize`. Should not be used in new code.
     #[rustc_builtin_macro]
-    #[stable(feature = "rust1", since = "1.0.0")]
+    #[unstable(
-    #[allow_internal_unstable(core_intrinsics, libstd_sys_internals, rt)]
+        feature = "rustc_encodable_decodable",
+        issue = "none",
+        soft,
+        reason = "derive macro for `rustc-serialize`; should not be used in new code"
+    )]
     #[deprecated(since = "1.52.0", note = "rustc-serialize is deprecated and no longer supported")]
     #[doc(hidden)] // While technically stable, using it is unstable, and deprecated. Hide it.
     pub macro RustcDecodable($item:item) {
         /* compiler built-in */
     }
 
-    /// Unstable implementation detail of the `rustc` compiler, do not use.
+    /// Derive macro for `rustc-serialize`. Should not be used in new code.
     #[rustc_builtin_macro]
-    #[stable(feature = "rust1", since = "1.0.0")]
+    #[unstable(
-    #[allow_internal_unstable(core_intrinsics, rt)]
+        feature = "rustc_encodable_decodable",
+        issue = "none",
+        soft,
+        reason = "derive macro for `rustc-serialize`; should not be used in new code"
+    )]
     #[deprecated(since = "1.52.0", note = "rustc-serialize is deprecated and no longer supported")]
     #[doc(hidden)] // While technically stable, using it is unstable, and deprecated. Hide it.
     pub macro RustcEncodable($item:item) {

library/core/src/prelude/v1.rs

@@ -69,7 +69,12 @@
 pub use crate::concat_bytes;
 
 // Do not `doc(inline)` these `doc(hidden)` items.
-#[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
+#[unstable(
+    feature = "rustc_encodable_decodable",
+    issue = "none",
+    soft,
+    reason = "unstable implementation detail of the `rustc` compiler, do not use"
+)]
 #[allow(deprecated)]
 pub use crate::macros::builtin::{RustcDecodable, RustcEncodable};
 

library/std/src/prelude/v1.rs

@@ -53,7 +53,12 @@
 pub use core::prelude::v1::concat_bytes;
 
 // Do not `doc(inline)` these `doc(hidden)` items.
-#[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
+#[unstable(
+    feature = "rustc_encodable_decodable",
+    issue = "none",
+    soft,
+    reason = "unstable implementation detail of the `rustc` compiler, do not use"
+)]
 #[allow(deprecated)]
 pub use core::prelude::v1::{RustcDecodable, RustcEncodable};
 

tests/run-make-fulldeps/pretty-expanded/input.rs

@@ -1,12 +1,8 @@
-#[crate_type="lib"]
-
 // #13544
 
-extern crate rustc_serialize;
+#[derive(Debug)] pub struct A;
-
+#[derive(Debug)] pub struct B(isize);
-#[derive(RustcEncodable)] pub struct A;
+#[derive(Debug)] pub struct C { x: isize }
-#[derive(RustcEncodable)] pub struct B(isize);
+#[derive(Debug)] pub enum D {}
-#[derive(RustcEncodable)] pub struct C { x: isize }
+#[derive(Debug)] pub enum E { y }
-#[derive(RustcEncodable)] pub enum D {}
+#[derive(Debug)] pub enum F { z(isize) }
-#[derive(RustcEncodable)] pub enum E { y }
-#[derive(RustcEncodable)] pub enum F { z(isize) }