Fully serialize AdtDef

This avoids needing to invoke the `adt_def` query during
the decoding of another query's result.

compiler/rustc_middle/src/arena.rs

@@ -9,7 +9,7 @@ macro_rules! arena_types {
             [] layout: rustc_target::abi::Layout,
             [] fn_abi: rustc_target::abi::call::FnAbi<'tcx, rustc_middle::ty::Ty<'tcx>>,
             // AdtDef are interned and compared by address
-            [] adt_def: rustc_middle::ty::AdtDef,
+            [decode] adt_def: rustc_middle::ty::AdtDef,
             [] steal_thir: rustc_data_structures::steal::Steal<rustc_middle::thir::Thir<'tcx>>,
             [] steal_mir: rustc_data_structures::steal::Steal<rustc_middle::mir::Body<'tcx>>,
             [decode] mir: rustc_middle::mir::Body<'tcx>,

compiler/rustc_middle/src/ty/adt.rs

@@ -11,7 +11,6 @@ use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_query_system::ich::StableHashingContext;
-use rustc_serialize::{self, Encodable, Encoder};
 use rustc_session::DataTypeKind;
 use rustc_span::symbol::sym;
 use rustc_target::abi::VariantIdx;
@@ -20,7 +19,7 @@ use std::cell::RefCell;
 use std::cmp::Ordering;
 use std::hash::{Hash, Hasher};
 use std::ops::Range;
-use std::{ptr, str};
+use std::str;
 
 use super::{
     Destructor, FieldDef, GenericPredicates, ReprOptions, Ty, TyCtxt, VariantDef, VariantDiscr,
@@ -30,7 +29,7 @@ use super::{
 pub struct AdtSizedConstraint<'tcx>(pub &'tcx [Ty<'tcx>]);
 
 bitflags! {
-    #[derive(HashStable)]
+    #[derive(HashStable, TyEncodable, TyDecodable)]
     pub struct AdtFlags: u32 {
         const NO_ADT_FLAGS        = 0;
         /// Indicates whether the ADT is an enum.
@@ -88,6 +87,7 @@ bitflags! {
 ///
 /// where `x` here represents the `DefId` of `S.x`. Then, the `DefId`
 /// can be used with [`TyCtxt::type_of()`] to get the type of the field.
+#[derive(TyEncodable, TyDecodable)]
 pub struct AdtDef {
     /// The `DefId` of the struct, enum or union item.
     pub did: DefId,
@@ -113,26 +113,23 @@ impl Ord for AdtDef {
     }
 }
 
+/// There should be only one AdtDef for each `did`, therefore
+/// it is fine to implement `PartialEq` only based on `did`.
 impl PartialEq for AdtDef {
-    // `AdtDef`s are always interned, and this is part of `TyS` equality.
     #[inline]
     fn eq(&self, other: &Self) -> bool {
-        ptr::eq(self, other)
+        self.did == other.did
     }
 }
 
 impl Eq for AdtDef {}
 
+/// There should be only one AdtDef for each `did`, therefore
+/// it is fine to implement `Hash` only based on `did`.
 impl Hash for AdtDef {
     #[inline]
     fn hash<H: Hasher>(&self, s: &mut H) {
-        (self as *const AdtDef).hash(s)
-    }
-}
-
-impl<S: Encoder> Encodable<S> for AdtDef {
-    fn encode(&self, s: &mut S) -> Result<(), S::Error> {
-        self.did.encode(s)
+        self.did.hash(s)
     }
 }
 
@@ -161,7 +158,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for AdtDef {
     }
 }
 
-#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, TyEncodable, TyDecodable)]
 pub enum AdtKind {
     Struct,
     Union,

compiler/rustc_middle/src/ty/codec.rs

@@ -16,7 +16,6 @@ use crate::thir;
 use crate::ty::subst::SubstsRef;
 use crate::ty::{self, List, Ty, TyCtxt};
 use rustc_data_structures::fx::FxHashMap;
-use rustc_hir::def_id::DefId;
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_span::Span;
 use std::hash::Hash;
@@ -308,13 +307,6 @@ macro_rules! impl_decodable_via_ref {
     }
 }
 
-impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::AdtDef {
-    fn decode(decoder: &mut D) -> Result<&'tcx Self, D::Error> {
-        let def_id = <DefId as Decodable<D>>::decode(decoder)?;
-        Ok(decoder.tcx().adt_def(def_id))
-    }
-}
-
 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<Ty<'tcx>> {
     fn decode(decoder: &mut D) -> Result<&'tcx Self, D::Error> {
         let len = decoder.read_usize()?;

compiler/rustc_middle/src/ty/context.rs

@@ -112,6 +112,7 @@ pub struct CtxtInterners<'tcx> {
     const_allocation: InternedSet<'tcx, Allocation>,
     bound_variable_kinds: InternedSet<'tcx, List<ty::BoundVariableKind>>,
     layout: InternedSet<'tcx, Layout>,
+    adt_def: InternedSet<'tcx, AdtDef>,
 }
 
 impl<'tcx> CtxtInterners<'tcx> {
@@ -132,6 +133,7 @@ impl<'tcx> CtxtInterners<'tcx> {
             const_allocation: Default::default(),
             bound_variable_kinds: Default::default(),
             layout: Default::default(),
+            adt_def: Default::default(),
         }
     }
 
@@ -1078,7 +1080,7 @@ impl<'tcx> TyCtxt<'tcx> {
         variants: IndexVec<VariantIdx, ty::VariantDef>,
         repr: ReprOptions,
     ) -> &'tcx ty::AdtDef {
-        self.arena.alloc(ty::AdtDef::new(self, did, kind, variants, repr))
+        self.intern_adt_def(ty::AdtDef::new(self, did, kind, variants, repr))
     }
 
     /// Allocates a read-only byte or string literal for `mir::interpret`.
@@ -2057,6 +2059,7 @@ direct_interners! {
     const_: mk_const(Const<'tcx>),
     const_allocation: intern_const_alloc(Allocation),
     layout: intern_layout(Layout),
+    adt_def: intern_adt_def(AdtDef),
 }
 
 macro_rules! slice_interners {

compiler/rustc_middle/src/ty/mod.rs

@@ -1472,7 +1472,7 @@ pub struct Destructor {
 }
 
 bitflags! {
-    #[derive(HashStable)]
+    #[derive(HashStable, TyEncodable, TyDecodable)]
     pub struct VariantFlags: u32 {
         const NO_VARIANT_FLAGS        = 0;
         /// Indicates whether the field list of this variant is `#[non_exhaustive]`.
@@ -1484,7 +1484,7 @@ bitflags! {
 }
 
 /// Definition of a variant -- a struct's fields or an enum variant.
-#[derive(Debug, HashStable)]
+#[derive(Debug, HashStable, TyEncodable, TyDecodable)]
 pub struct VariantDef {
     /// `DefId` that identifies the variant itself.
     /// If this variant belongs to a struct or union, then this is a copy of its `DefId`.
@@ -1586,7 +1586,7 @@ pub enum VariantDiscr {
     Relative(u32),
 }
 
-#[derive(Debug, HashStable)]
+#[derive(Debug, HashStable, TyEncodable, TyDecodable)]
 pub struct FieldDef {
     pub did: DefId,
     #[stable_hasher(project(name))]