Rework `rustc_serialize`

- Move the type parameter from `encode` and `decode` methods to
  the trait.
- Remove `UseSpecialized(En|De)codable` traits.
- Remove blanket impls for references.
- Add `RefDecodable` trait to allow deserializing to arena-allocated
  references safely.
- Remove ability to (de)serialize HIR.
- Create proc-macros `(Ty)?(En|De)codable` to help implement these new
  traits.

5 files changed, 11 insertions, 6 deletions

diff --git a/src/librustc_session/Cargo.toml b/src/librustc_session/Cargo.toml
index 35c227df850..cb6626d0f4b 100644
--- a/src/librustc_session/Cargo.toml
+++ b/src/librustc_session/Cargo.toml
@@ -12,6 +12,7 @@ path = "lib.rs"
 bitflags = "1.2.1"
 getopts = "0.2"
 log = { package = "tracing", version = "0.1" }
+rustc_macros = { path = "../librustc_macros" }
 rustc_errors = { path = "../librustc_errors" }
 rustc_feature = { path = "../librustc_feature" }
 rustc_target = { path = "../librustc_target" }
diff --git a/src/librustc_session/config.rs b/src/librustc_session/config.rs
index 9fcdd46539c..c26c9bde3ee 100644
--- a/src/librustc_session/config.rs
+++ b/src/librustc_session/config.rs
@@ -39,7 +39,7 @@ pub struct Config {
 }
 
 bitflags! {
-    #[derive(Default, RustcEncodable, RustcDecodable)]
+    #[derive(Default, Encodable, Decodable)]
     pub struct SanitizerSet: u8 {
         const ADDRESS = 1 << 0;
         const LEAK    = 1 << 1;
@@ -194,7 +194,8 @@ impl SwitchWithOptPath {
     }
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[derive(Encodable, Decodable)]
 pub enum SymbolManglingVersion {
     Legacy,
     V0,
@@ -209,7 +210,8 @@ pub enum DebugInfo {
     Full,
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, PartialOrd, Ord, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, PartialOrd, Ord)]
+#[derive(Encodable, Decodable)]
 pub enum OutputType {
     Bitcode,
     Assembly,
@@ -672,7 +674,7 @@ pub enum EntryFnType {
 
 impl_stable_hash_via_hash!(EntryFnType);
 
-#[derive(Copy, PartialEq, PartialOrd, Clone, Ord, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Copy, PartialEq, PartialOrd, Clone, Ord, Eq, Hash, Debug, Encodable, Decodable)]
 pub enum CrateType {
     Executable,
     Dylib,
diff --git a/src/librustc_session/lib.rs b/src/librustc_session/lib.rs
index be9d2e7be27..c2ea141a06f 100644
--- a/src/librustc_session/lib.rs
+++ b/src/librustc_session/lib.rs
@@ -3,6 +3,8 @@
 
 #[macro_use]
 extern crate bitflags;
+#[macro_use]
+extern crate rustc_macros;
 
 pub mod cgu_reuse_tracker;
 pub mod utils;
diff --git a/src/librustc_session/search_paths.rs b/src/librustc_session/search_paths.rs
index 4ff06acaa1f..e12364b7dac 100644
--- a/src/librustc_session/search_paths.rs
+++ b/src/librustc_session/search_paths.rs
@@ -33,7 +33,7 @@ impl SearchPathFile {
     }
 }
 
-#[derive(PartialEq, Clone, Copy, Debug, Hash, Eq, RustcEncodable, RustcDecodable)]
+#[derive(PartialEq, Clone, Copy, Debug, Hash, Eq, Encodable, Decodable)]
 pub enum PathKind {
     Native,
     Crate,
diff --git a/src/librustc_session/utils.rs b/src/librustc_session/utils.rs
index b97308c22cb..15447c01d1e 100644
--- a/src/librustc_session/utils.rs
+++ b/src/librustc_session/utils.rs
@@ -10,7 +10,7 @@ impl Session {
     }
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Encodable, Decodable)]
 pub enum NativeLibKind {
     /// Static library (e.g. `libfoo.a` on Linux or `foo.lib` on Windows/MSVC) included
     /// when linking a final binary, but not when archiving an rlib.