Auto merge of #65541 - eddyb:spanned-inferred-outlives, r=<try>

rustc: add `Span`s to `inferred_outlives_of` predicates.

*Based on #65535.*

This would simplify #59789, and I suspect it has some potential in diagnostics (although we don't seem to use the predicate `Span`s much atm).

Author: bors

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() }
         }
 
@@ -184,31 +184,28 @@ 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`).
-        query inferred_outlives_of(_: DefId) -> &'tcx [ty::Predicate<'tcx>] {}
+        query inferred_outlives_of(_: DefId) -> &'tcx [(ty::Predicate<'tcx>, Span)] {}
 
         /// Maps from the `DefId` of a trait to the list of
         /// super-predicates. This is a subset of the full list of
         /// predicates. We store these in a separate map because we must
         /// 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,
@@ -1139,7 +1136,7 @@ pub struct CratePredicatesMap<'tcx> {
     /// For each struct with outlive bounds, maps to a vector of the
     /// predicate of its outlive bounds. If an item has no outlives
     /// bounds, it will have no entry.
-    pub predicates: FxHashMap<DefId, &'tcx [ty::Predicate<'tcx>]>,
+    pub predicates: FxHashMap<DefId, &'tcx [(ty::Predicate<'tcx>, Span)]>,
 }
 
 impl<'tcx> AsRef<Predicate<'tcx>> for Predicate<'tcx> {
@@ -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(..) |
@@ -1518,10 +1518,10 @@ declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMEN
 
 impl ExplicitOutlivesRequirements {
     fn lifetimes_outliving_lifetime<'tcx>(
-        inferred_outlives: &'tcx [ty::Predicate<'tcx>],
+        inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
         index: u32,
     ) -> Vec<ty::Region<'tcx>> {
-        inferred_outlives.iter().filter_map(|pred| {
+        inferred_outlives.iter().filter_map(|(pred, _)| {
             match pred {
                 ty::Predicate::RegionOutlives(outlives) => {
                     let outlives = outlives.skip_binder();
@@ -1538,10 +1538,10 @@ impl ExplicitOutlivesRequirements {
     }
 
     fn lifetimes_outliving_type<'tcx>(
-        inferred_outlives: &'tcx [ty::Predicate<'tcx>],
+        inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
         index: u32,
     ) -> Vec<ty::Region<'tcx>> {
-        inferred_outlives.iter().filter_map(|pred| {
+        inferred_outlives.iter().filter_map(|(pred, _)| {
             match pred {
                 ty::Predicate::TypeOutlives(outlives) => {
                     let outlives = outlives.skip_binder();
@@ -1560,7 +1560,7 @@ impl ExplicitOutlivesRequirements {
         &self,
         param: &'tcx hir::GenericParam,
         tcx: TyCtxt<'tcx>,
-        inferred_outlives: &'tcx [ty::Predicate<'tcx>],
+        inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
         ty_generics: &'tcx ty::Generics,
     ) -> Vec<ty::Region<'tcx>> {
         let index = ty_generics.param_def_id_to_index[

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;