rustc: arena-allocate the slice in ty::GenericsPredicate, not the whole struct.

src/librustc/arena.rs

@@ -98,7 +98,6 @@ macro_rules! arena_types {
                 rustc::hir::def_id::DefId,
             >,
             [few] resolve_lifetimes: rustc::middle::resolve_lifetime::ResolveLifetimes,
-            [decode] generic_predicates: rustc::ty::GenericPredicates<'tcx>,
             [few] lint_levels: rustc::lint::LintLevelMap,
             [few] stability_index: rustc::middle::stability::Index<'tcx>,
             [few] features: syntax::feature_gate::Features,

src/librustc/query/mod.rs

@@ -61,7 +61,7 @@ rustc_queries! {
         /// predicate gets in the way of some checks, which are intended
         /// to operate over only the actual where-clauses written by the
         /// user.)
-        query predicates_of(key: DefId) -> &'tcx ty::GenericPredicates<'tcx> {
+        query predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
             cache_on_disk_if { key.is_local() }
         }
 
@@ -184,12 +184,10 @@ rustc_queries! {
         /// predicates (where-clauses) directly defined on it. This is
         /// equal to the `explicit_predicates_of` predicates plus the
         /// `inferred_outlives_of` predicates.
-        query predicates_defined_on(_: DefId)
-            -> &'tcx ty::GenericPredicates<'tcx> {}
+        query predicates_defined_on(_: DefId) -> ty::GenericPredicates<'tcx> {}
 
         /// Returns the predicates written explicitly by the user.
-        query explicit_predicates_of(_: DefId)
-            -> &'tcx ty::GenericPredicates<'tcx> {}
+        query explicit_predicates_of(_: DefId) -> ty::GenericPredicates<'tcx> {}
 
         /// Returns the inferred outlives predicates (e.g., for `struct
         /// Foo<'a, T> { x: &'a T }`, this would return `T: 'a`).
@@ -201,14 +199,13 @@ rustc_queries! {
         /// evaluate them even during type conversion, often before the
         /// full predicates are available (note that supertraits have
         /// additional acyclicity requirements).
-        query super_predicates_of(key: DefId) -> &'tcx ty::GenericPredicates<'tcx> {
+        query super_predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
             desc { |tcx| "computing the supertraits of `{}`", tcx.def_path_str(key) }
         }
 
         /// To avoid cycles within the predicates of a single item we compute
         /// per-type-parameter predicates for resolving `T::AssocTy`.
-        query type_param_predicates(key: (DefId, DefId))
-            -> &'tcx ty::GenericPredicates<'tcx> {
+        query type_param_predicates(key: (DefId, DefId)) -> ty::GenericPredicates<'tcx> {
             no_force
             desc { |tcx| "computing the bounds for type parameter `{}`", {
                 let id = tcx.hir().as_local_hir_id(key.1).unwrap();

src/librustc/traits/specialize/mod.rs

@@ -419,7 +419,7 @@ fn to_pretty_impl_header(tcx: TyCtxt<'_>, impl_def_id: DefId) -> Option<String>
 
     // The predicates will contain default bounds like `T: Sized`. We need to
     // remove these bounds, and add `T: ?Sized` to any untouched type parameters.
-    let predicates = &tcx.predicates_of(impl_def_id).predicates;
+    let predicates = tcx.predicates_of(impl_def_id).predicates;
     let mut pretty_predicates = Vec::with_capacity(
         predicates.len() + types_without_default_bounds.len());
 

src/librustc/ty/codec.rs

@@ -16,6 +16,7 @@ use std::intrinsics;
 use crate::ty::{self, Ty, TyCtxt};
 use crate::ty::subst::SubstsRef;
 use crate::mir::interpret::Allocation;
+use syntax_pos::Span;
 
 /// The shorthand encoding uses an enum's variant index `usize`
 /// and is offset by this value so it never matches a real variant.
@@ -92,16 +93,16 @@ pub fn encode_with_shorthand<E, T, M>(encoder: &mut E,
     Ok(())
 }
 
-pub fn encode_predicates<'tcx, E, C>(encoder: &mut E,
-                                     predicates: &ty::GenericPredicates<'tcx>,
-                                     cache: C)
-                                     -> Result<(), E::Error>
+pub fn encode_spanned_predicates<'tcx, E, C>(
+    encoder: &mut E,
+    predicates: &'tcx [(ty::Predicate<'tcx>, Span)],
+    cache: C,
+) -> Result<(), E::Error>
     where E: TyEncoder,
           C: for<'b> Fn(&'b mut E) -> &'b mut FxHashMap<ty::Predicate<'tcx>, usize>,
 {
-    predicates.parent.encode(encoder)?;
-    predicates.predicates.len().encode(encoder)?;
-    for (predicate, span) in &predicates.predicates {
+    predicates.len().encode(encoder)?;
+    for (predicate, span) in predicates {
         encode_with_shorthand(encoder, predicate, &cache)?;
         span.encode(encoder)?;
     }
@@ -182,13 +183,15 @@ where
 }
 
 #[inline]
-pub fn decode_predicates<D>(decoder: &mut D) -> Result<ty::GenericPredicates<'tcx>, D::Error>
+pub fn decode_spanned_predicates<D>(
+    decoder: &mut D,
+) -> Result<&'tcx [(ty::Predicate<'tcx>, Span)], D::Error>
 where
     D: TyDecoder<'tcx>,
 {
-    Ok(ty::GenericPredicates {
-        parent: Decodable::decode(decoder)?,
-        predicates: (0..decoder.read_usize()?).map(|_| {
+    let tcx = decoder.tcx();
+    Ok(tcx.arena.alloc_from_iter(
+        (0..decoder.read_usize()?).map(|_| {
             // Handle shorthands first, if we have an usize > 0x80.
             let predicate = if decoder.positioned_at_shorthand() {
                 let pos = decoder.read_usize()?;
@@ -202,7 +205,7 @@ where
             Ok((predicate, Decodable::decode(decoder)?))
         })
         .collect::<Result<Vec<_>, _>>()?,
-    })
+    ))
 }
 
 #[inline]
@@ -339,6 +342,8 @@ macro_rules! implement_ty_decoder {
             use $crate::ty::subst::SubstsRef;
             use $crate::hir::def_id::{CrateNum};
 
+            use syntax_pos::Span;
+
             use super::$DecoderName;
 
             impl<$($typaram ),*> Decoder for $DecoderName<$($typaram),*> {
@@ -393,11 +398,11 @@ macro_rules! implement_ty_decoder {
                 }
             }
 
-            impl<$($typaram),*> SpecializedDecoder<ty::GenericPredicates<'tcx>>
+            impl<$($typaram),*> SpecializedDecoder<&'tcx [(ty::Predicate<'tcx>, Span)]>
             for $DecoderName<$($typaram),*> {
                 fn specialized_decode(&mut self)
-                                      -> Result<ty::GenericPredicates<'tcx>, Self::Error> {
-                    decode_predicates(self)
+                                      -> Result<&'tcx [(ty::Predicate<'tcx>, Span)], Self::Error> {
+                    decode_spanned_predicates(self)
                 }
             }
 

src/librustc/ty/context.rs

@@ -148,10 +148,6 @@ impl<'tcx> CtxtInterners<'tcx> {
     }
 }
 
-pub struct Common<'tcx> {
-    pub empty_predicates: ty::GenericPredicates<'tcx>,
-}
-
 pub struct CommonTypes<'tcx> {
     pub unit: Ty<'tcx>,
     pub bool: Ty<'tcx>,
@@ -1039,9 +1035,6 @@ pub struct GlobalCtxt<'tcx> {
 
     pub prof: SelfProfilerRef,
 
-    /// Common objects.
-    pub common: Common<'tcx>,
-
     /// Common types, pre-interned for your convenience.
     pub types: CommonTypes<'tcx>,
 
@@ -1213,12 +1206,6 @@ impl<'tcx> TyCtxt<'tcx> {
             s.fatal(&err);
         });
         let interners = CtxtInterners::new(&arenas.interner);
-        let common = Common {
-            empty_predicates: ty::GenericPredicates {
-                parent: None,
-                predicates: vec![],
-            },
-        };
         let common_types = CommonTypes::new(&interners);
         let common_lifetimes = CommonLifetimes::new(&interners);
         let common_consts = CommonConsts::new(&interners, &common_types);
@@ -1273,7 +1260,6 @@ impl<'tcx> TyCtxt<'tcx> {
             interners,
             dep_graph,
             prof: s.prof.clone(),
-            common,
             types: common_types,
             lifetimes: common_lifetimes,
             consts: common_consts,

src/librustc/ty/mod.rs

@@ -1018,15 +1018,12 @@ impl<'tcx> Generics {
 }
 
 /// Bounds on generics.
-#[derive(Clone, Default, Debug, HashStable)]
+#[derive(Copy, Clone, Default, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub struct GenericPredicates<'tcx> {
     pub parent: Option<DefId>,
-    pub predicates: Vec<(Predicate<'tcx>, Span)>,
+    pub predicates: &'tcx [(Predicate<'tcx>, Span)],
 }
 
-impl<'tcx> rustc_serialize::UseSpecializedEncodable for GenericPredicates<'tcx> {}
-impl<'tcx> rustc_serialize::UseSpecializedDecodable for GenericPredicates<'tcx> {}
-
 impl<'tcx> GenericPredicates<'tcx> {
     pub fn instantiate(
         &self,
@@ -2321,7 +2318,7 @@ impl<'tcx> AdtDef {
     }
 
     #[inline]
-    pub fn predicates(&self, tcx: TyCtxt<'tcx>) -> &'tcx GenericPredicates<'tcx> {
+    pub fn predicates(&self, tcx: TyCtxt<'tcx>) -> GenericPredicates<'tcx> {
         tcx.predicates_of(self.did)
     }
 
@@ -2561,7 +2558,7 @@ impl<'tcx> AdtDef {
                     def_id: sized_trait,
                     substs: tcx.mk_substs_trait(ty, &[])
                 }).to_predicate();
-                let predicates = &tcx.predicates_of(self.did).predicates;
+                let predicates = tcx.predicates_of(self.did).predicates;
                 if predicates.iter().any(|(p, _)| *p == sized_predicate) {
                     vec![]
                 } else {

src/librustc/ty/query/on_disk_cache.rs

@@ -882,15 +882,16 @@ where
     }
 }
 
-impl<'a, 'tcx, E> SpecializedEncoder<ty::GenericPredicates<'tcx>> for CacheEncoder<'a, 'tcx, E>
+impl<'a, 'tcx, E> SpecializedEncoder<&'tcx [(ty::Predicate<'tcx>, Span)]>
+    for CacheEncoder<'a, 'tcx, E>
 where
     E: 'a + TyEncoder,
 {
     #[inline]
     fn specialized_encode(&mut self,
-                          predicates: &ty::GenericPredicates<'tcx>)
+                          predicates: &&'tcx [(ty::Predicate<'tcx>, Span)])
                           -> Result<(), Self::Error> {
-        ty_codec::encode_predicates(self, predicates,
+        ty_codec::encode_spanned_predicates(self, predicates,
             |encoder| &mut encoder.predicate_shorthands)
     }
 }

src/librustc/ty/structural_impls.rs

@@ -1218,12 +1218,6 @@ EnumTypeFoldableImpl! {
     }
 }
 
-BraceStructTypeFoldableImpl! {
-    impl<'tcx> TypeFoldable<'tcx> for ty::GenericPredicates<'tcx> {
-        parent, predicates
-    }
-}
-
 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
         // This code is hot enough that it's worth specializing for a list of

src/librustc_lint/builtin.rs

@@ -1241,7 +1241,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TrivialConstraints {
         if cx.tcx.features().trivial_bounds {
             let def_id = cx.tcx.hir().local_def_id(item.hir_id);
             let predicates = cx.tcx.predicates_of(def_id);
-            for &(predicate, span) in &predicates.predicates {
+            for &(predicate, span) in predicates.predicates {
                 let predicate_kind_name = match predicate {
                     Trait(..) => "Trait",
                     TypeOutlives(..) |

src/librustc_lint/unused.rs

@@ -156,7 +156,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
                 }
                 ty::Opaque(def, _) => {
                     let mut has_emitted = false;
-                    for (predicate, _) in &cx.tcx.predicates_of(def).predicates {
+                    for (predicate, _) in cx.tcx.predicates_of(def).predicates {
                         if let ty::Predicate::Trait(ref poly_trait_predicate) = predicate {
                             let trait_ref = poly_trait_predicate.skip_binder().trait_ref;
                             let def_id = trait_ref.def_id;

src/librustc_metadata/cstore_impl.rs

@@ -97,11 +97,9 @@ provide! { <'tcx> tcx, def_id, other, cdata,
     generics_of => {
         tcx.arena.alloc(cdata.get_generics(def_id.index, tcx.sess))
     }
-    predicates_of => { tcx.arena.alloc(cdata.get_predicates(def_id.index, tcx)) }
-    predicates_defined_on => {
-        tcx.arena.alloc(cdata.get_predicates_defined_on(def_id.index, tcx))
-    }
-    super_predicates_of => { tcx.arena.alloc(cdata.get_super_predicates(def_id.index, tcx)) }
+    predicates_of => { cdata.get_predicates(def_id.index, tcx) }
+    predicates_defined_on => { cdata.get_predicates_defined_on(def_id.index, tcx) }
+    super_predicates_of => { cdata.get_super_predicates(def_id.index, tcx) }
     trait_def => {
         tcx.arena.alloc(cdata.get_trait_def(def_id.index, tcx.sess))
     }

src/librustc_metadata/encoder.rs

@@ -243,11 +243,11 @@ impl<'tcx> SpecializedEncoder<interpret::AllocId> for EncodeContext<'tcx> {
     }
 }
 
-impl<'tcx> SpecializedEncoder<ty::GenericPredicates<'tcx>> for EncodeContext<'tcx> {
+impl<'tcx> SpecializedEncoder<&'tcx [(ty::Predicate<'tcx>, Span)]> for EncodeContext<'tcx> {
     fn specialized_encode(&mut self,
-                          predicates: &ty::GenericPredicates<'tcx>)
+                          predicates: &&'tcx [(ty::Predicate<'tcx>, Span)])
                           -> Result<(), Self::Error> {
-        ty_codec::encode_predicates(self, predicates, |ecx| &mut ecx.predicate_shorthands)
+        ty_codec::encode_spanned_predicates(self, predicates, |ecx| &mut ecx.predicate_shorthands)
     }
 }
 
@@ -826,13 +826,13 @@ impl EncodeContext<'tcx> {
 
     fn encode_predicates(&mut self, def_id: DefId) {
         debug!("EncodeContext::encode_predicates({:?})", def_id);
-        record!(self.per_def.predicates[def_id] <- &*self.tcx.predicates_of(def_id));
+        record!(self.per_def.predicates[def_id] <- self.tcx.predicates_of(def_id));
     }
 
     fn encode_predicates_defined_on(&mut self, def_id: DefId) {
         debug!("EncodeContext::encode_predicates_defined_on({:?})", def_id);
         record!(self.per_def.predicates_defined_on[def_id] <-
-            &*self.tcx.predicates_defined_on(def_id))
+            self.tcx.predicates_defined_on(def_id))
     }
 
     fn encode_info_for_trait_item(&mut self, def_id: DefId) {
@@ -1166,14 +1166,14 @@ impl EncodeContext<'tcx> {
                     paren_sugar: trait_def.paren_sugar,
                     has_auto_impl: self.tcx.trait_is_auto(def_id),
                     is_marker: trait_def.is_marker,
-                    super_predicates: self.lazy(&*tcx.super_predicates_of(def_id)),
+                    super_predicates: self.lazy(tcx.super_predicates_of(def_id)),
                 };
 
                 EntryKind::Trait(self.lazy(data))
             }
             hir::ItemKind::TraitAlias(..) => {
                 let data = TraitAliasData {
-                    super_predicates: self.lazy(&*tcx.super_predicates_of(def_id)),
+                    super_predicates: self.lazy(tcx.super_predicates_of(def_id)),
                 };
 
                 EntryKind::TraitAlias(self.lazy(data))

src/librustc_mir/transform/qualify_min_const_fn.rs

@@ -14,7 +14,7 @@ pub fn is_min_const_fn(tcx: TyCtxt<'tcx>, def_id: DefId, body: &'a Body<'tcx>) -
     let mut current = def_id;
     loop {
         let predicates = tcx.predicates_of(current);
-        for (predicate, _) in &predicates.predicates {
+        for (predicate, _) in predicates.predicates {
             match predicate {
                 | Predicate::RegionOutlives(_)
                 | Predicate::TypeOutlives(_)

src/librustc_privacy/lib.rs

@@ -64,7 +64,7 @@ trait DefIdVisitor<'tcx> {
     fn visit_trait(&mut self, trait_ref: TraitRef<'tcx>) -> bool {
         self.skeleton().visit_trait(trait_ref)
     }
-    fn visit_predicates(&mut self, predicates: &ty::GenericPredicates<'tcx>) -> bool {
+    fn visit_predicates(&mut self, predicates: ty::GenericPredicates<'tcx>) -> bool {
         self.skeleton().visit_predicates(predicates)
     }
 }
@@ -88,7 +88,7 @@ where
         (!self.def_id_visitor.shallow() && substs.visit_with(self))
     }
 
-    fn visit_predicates(&mut self, predicates: &ty::GenericPredicates<'tcx>) -> bool {
+    fn visit_predicates(&mut self, predicates: ty::GenericPredicates<'tcx>) -> bool {
         let ty::GenericPredicates { parent: _, predicates } = predicates;
         for (predicate, _span) in predicates {
             match predicate {

src/librustc_traits/lowering/mod.rs

@@ -218,7 +218,7 @@ fn program_clauses_for_trait(tcx: TyCtxt<'_>, def_id: DefId) -> Clauses<'_> {
 
     let implemented_from_env = Clause::ForAll(ty::Binder::bind(implemented_from_env));
 
-    let predicates = &tcx.predicates_defined_on(def_id).predicates;
+    let predicates = tcx.predicates_defined_on(def_id).predicates;
 
     // Warning: these where clauses are not substituted for bound vars yet,
     // so that we don't need to adjust binders in the `FromEnv` rules below
@@ -319,7 +319,7 @@ fn program_clauses_for_impl(tcx: TyCtxt<'tcx>, def_id: DefId) -> Clauses<'tcx> {
     let trait_pred = ty::TraitPredicate { trait_ref }.lower();
 
     // `WC`
-    let predicates = &tcx.predicates_of(def_id).predicates;
+    let predicates = tcx.predicates_of(def_id).predicates;
     let where_clauses = predicates
         .iter()
         .map(|(wc, _)| wc.lower())

src/librustc_typeck/astconv.rs

@@ -54,8 +54,7 @@ pub trait AstConv<'tcx> {
     /// but this can lead to cycle errors. The problem is that we have
     /// to do this resolution *in order to create the predicates in
     /// the first place*. Hence, we have this "special pass".
-    fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
-                                 -> &'tcx ty::GenericPredicates<'tcx>;
+    fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> ty::GenericPredicates<'tcx>;
 
     /// Returns the lifetime to use when a lifetime is omitted (and not elided).
     fn re_infer(