convert inherent-impl-related things to on-demand queries

There are now 3 queries:

- inherent_impls(def-id): for a given type, get a `Rc<Vec<DefId>>` with
  all its inherent impls. This internally uses `crate_inherent_impls`,
  doing some hacks to keep the current deps (which, btw, are not clearly
  correct).
- crate_inherent_impls(crate): gathers up a map from types
  to `Rc<Vec<DefId>>`, touching the entire krate, possibly generating
  errors.
- crate_inherent_impls_overlap_check(crate): performs overlap checks
  between the inherent impls for a given type, generating errors.

src/librustc/dep_graph/dep_node.rs

@@ -74,7 +74,6 @@ pub enum DepNode<D: Clone + Debug> {
     CoherenceCheckImpl(D),
     CoherenceOverlapCheck(D),
     CoherenceOverlapCheckSpecial(D),
-    CoherenceOverlapInherentCheck(D),
     CoherenceOrphanCheck(D),
     Variance,
     WfCheck(D),
@@ -251,7 +250,6 @@ impl<D: Clone + Debug> DepNode<D> {
             CoherenceCheckImpl(ref d) => op(d).map(CoherenceCheckImpl),
             CoherenceOverlapCheck(ref d) => op(d).map(CoherenceOverlapCheck),
             CoherenceOverlapCheckSpecial(ref d) => op(d).map(CoherenceOverlapCheckSpecial),
-            CoherenceOverlapInherentCheck(ref d) => op(d).map(CoherenceOverlapInherentCheck),
             CoherenceOrphanCheck(ref d) => op(d).map(CoherenceOrphanCheck),
             WfCheck(ref d) => op(d).map(WfCheck),
             TypeckItemType(ref d) => op(d).map(TypeckItemType),

src/librustc/dep_graph/dep_tracking_map.rs

@@ -81,21 +81,6 @@ impl<M: DepTrackingMapConfig> DepTrackingMap<M> {
     pub fn keys(&self) -> Vec<M::Key> {
         self.map.keys().cloned().collect()
     }
-
-    /// Append `elem` to the vector stored for `k`, creating a new vector if needed.
-    /// This is considered a write to `k`.
-    ///
-    /// NOTE: Caution is required when using this method. You should
-    /// be sure that nobody is **reading from the vector** while you
-    /// are writing to it. Eventually, it'd be nice to remove this.
-    pub fn push<E: Clone>(&mut self, k: M::Key, elem: E)
-        where M: DepTrackingMapConfig<Value=Vec<E>>
-    {
-        self.write(&k);
-        self.map.entry(k)
-                .or_insert(Vec::new())
-                .push(elem);
-    }
 }
 
 impl<M: DepTrackingMapConfig> MemoizationMap for RefCell<DepTrackingMap<M>> {

src/librustc/middle/cstore.rs

@@ -176,7 +176,6 @@ pub trait CrateStore {
     fn item_generics_cloned(&self, def: DefId) -> ty::Generics;
     fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute>;
     fn fn_arg_names(&self, did: DefId) -> Vec<ast::Name>;
-    fn inherent_implementations_for_type(&self, def_id: DefId) -> Vec<DefId>;
 
     // trait info
     fn implementations_of_trait(&self, filter: Option<DefId>) -> Vec<DefId>;
@@ -310,7 +309,6 @@ impl CrateStore for DummyCrateStore {
         { bug!("item_generics_cloned") }
     fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute> { bug!("item_attrs") }
     fn fn_arg_names(&self, did: DefId) -> Vec<ast::Name> { bug!("fn_arg_names") }
-    fn inherent_implementations_for_type(&self, def_id: DefId) -> Vec<DefId> { vec![] }
 
     // trait info
     fn implementations_of_trait(&self, filter: Option<DefId>) -> Vec<DefId> { vec![] }

src/librustc/ty/maps.rs

@@ -12,7 +12,7 @@ use dep_graph::{DepGraph, DepNode, DepTrackingMap, DepTrackingMapConfig};
 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
 use middle::const_val::ConstVal;
 use mir;
-use ty::{self, Ty, TyCtxt};
+use ty::{self, CrateInherentImpls, Ty, TyCtxt};
 
 use rustc_data_structures::indexed_vec::IndexVec;
 use std::cell::{RefCell, RefMut};
@@ -176,9 +176,15 @@ impl<'tcx> QueryDescription for queries::coherent_trait<'tcx> {
     }
 }
 
-impl<'tcx> QueryDescription for queries::coherent_inherent_impls<'tcx> {
+impl<'tcx> QueryDescription for queries::crate_inherent_impls<'tcx> {
+    fn describe(_: TyCtxt, k: CrateNum) -> String {
+        format!("all inherent impls defined in crate `{:?}`", k)
+    }
+}
+
+impl<'tcx> QueryDescription for queries::crate_inherent_impls_overlap_check<'tcx> {
     fn describe(_: TyCtxt, _: CrateNum) -> String {
-        format!("coherence checking all inherent impls")
+        format!("check for overlap between inherent impls defined in this crate")
     }
 }
 
@@ -368,7 +374,7 @@ define_maps! { <'tcx>
     /// Maps a DefId of a type to a list of its inherent impls.
     /// Contains implementations of methods that are inherent to a type.
     /// Methods in these implementations don't need to be exported.
-    pub inherent_impls: InherentImpls(DefId) -> Vec<DefId>,
+    pub inherent_impls: InherentImpls(DefId) -> Rc<Vec<DefId>>,
 
     /// Maps from the def-id of a function/method or const/static
     /// to its MIR. Mutation is done at an item granularity to
@@ -400,7 +406,15 @@ define_maps! { <'tcx>
 
     pub coherent_trait: coherent_trait_dep_node((CrateNum, DefId)) -> (),
 
-    pub coherent_inherent_impls: coherent_inherent_impls_dep_node(CrateNum) -> (),
+    /// Gets a complete map from all types to their inherent impls.
+    /// Not meant to be used directly outside of coherence.
+    /// (Defined only for LOCAL_CRATE)
+    pub crate_inherent_impls: crate_inherent_impls_dep_node(CrateNum) -> CrateInherentImpls,
+
+    /// Checks all types in the krate for overlap in their inherent impls. Reports errors.
+    /// Not meant to be used directly outside of coherence.
+    /// (Defined only for LOCAL_CRATE)
+    pub crate_inherent_impls_overlap_check: crate_inherent_impls_dep_node(CrateNum) -> (),
 
     /// Results of evaluating monomorphic constants embedded in
     /// other items, such as enum variant explicit discriminants.
@@ -413,7 +427,7 @@ fn coherent_trait_dep_node((_, def_id): (CrateNum, DefId)) -> DepNode<DefId> {
     DepNode::CoherenceCheckTrait(def_id)
 }
 
-fn coherent_inherent_impls_dep_node(_: CrateNum) -> DepNode<DefId> {
+fn crate_inherent_impls_dep_node(_: CrateNum) -> DepNode<DefId> {
     DepNode::Coherence
 }
 

src/librustc/ty/mod.rs

@@ -31,7 +31,7 @@ use ty::subst::{Subst, Substs};
 use ty::util::IntTypeExt;
 use ty::walk::TypeWalker;
 use util::common::MemoizationMap;
-use util::nodemap::{NodeSet, FxHashMap};
+use util::nodemap::{NodeSet, DefIdMap, FxHashMap};
 
 use serialize::{self, Encodable, Encoder};
 use std::borrow::Cow;
@@ -2345,34 +2345,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         def.flags.get().intersects(TraitFlags::HAS_DEFAULT_IMPL)
     }
 
-    /// Populates the type context with all the inherent implementations for
-    /// the given type if necessary.
-    pub fn populate_inherent_implementations_for_type_if_necessary(self,
-                                                                   span: Span,
-                                                                   type_id: DefId) {
-        if type_id.is_local() {
-            // Make sure coherence of inherent impls ran already.
-            ty::queries::coherent_inherent_impls::force(self, span, LOCAL_CRATE);
-            return
-        }
-
-        // The type is not local, hence we are reading this out of
-        // metadata and don't need to track edges.
-        let _ignore = self.dep_graph.in_ignore();
-
-        if self.populated_external_types.borrow().contains(&type_id) {
-            return
-        }
-
-        debug!("populate_inherent_implementations_for_type_if_necessary: searching for {:?}",
-               type_id);
-
-        let inherent_impls = self.sess.cstore.inherent_implementations_for_type(type_id);
-
-        self.maps.inherent_impls.borrow_mut().insert(type_id, inherent_impls);
-        self.populated_external_types.borrow_mut().insert(type_id);
-    }
-
     /// Populates the type context with all the implementations for the given
     /// trait if necessary.
     pub fn populate_implementations_for_trait_if_necessary(self, trait_id: DefId) {
@@ -2637,3 +2609,16 @@ pub fn provide(providers: &mut ty::maps::Providers) {
         ..*providers
     };
 }
+
+
+/// A map for the local crate mapping each type to a vector of its
+/// inherent impls. This is not meant to be used outside of coherence;
+/// rather, you should request the vector for a specific type via
+/// `ty::queries::inherent_impls::get(def_id)` so as to minimize your
+/// dependencies (constructing this map requires touching the entire
+/// crate).
+#[derive(Clone, Debug)]
+pub struct CrateInherentImpls {
+    pub inherent_impls: DefIdMap<Rc<Vec<DefId>>>,
+}
+

src/librustc_metadata/cstore_impl.rs

@@ -109,6 +109,7 @@ provide! { <'tcx> tcx, def_id, cdata
     typeck_tables => { cdata.item_body_tables(def_id.index, tcx) }
     closure_kind => { cdata.closure_kind(def_id.index) }
     closure_type => { cdata.closure_ty(def_id.index, tcx) }
+    inherent_impls => { Rc::new(cdata.get_inherent_implementations_for_type(def_id.index)) }
 }
 
 impl CrateStore for cstore::CStore {
@@ -162,12 +163,6 @@ impl CrateStore for cstore::CStore {
         self.get_crate_data(did.krate).get_fn_arg_names(did.index)
     }
 
-    fn inherent_implementations_for_type(&self, def_id: DefId) -> Vec<DefId>
-    {
-        self.dep_graph.read(DepNode::MetaData(def_id));
-        self.get_crate_data(def_id.krate).get_inherent_implementations_for_type(def_id.index)
-    }
-
     fn implementations_of_trait(&self, filter: Option<DefId>) -> Vec<DefId>
     {
         if let Some(def_id) = filter {

src/librustc_typeck/check/method/probe.rs

@@ -479,14 +479,9 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
     }
 
     fn assemble_inherent_impl_candidates_for_type(&mut self, def_id: DefId) {
-        // Read the inherent implementation candidates for this type from the
-        // metadata if necessary.
-        self.tcx.populate_inherent_implementations_for_type_if_necessary(self.span, def_id);
-
-        if let Some(impl_infos) = self.tcx.maps.inherent_impls.borrow().get(&def_id) {
-            for &impl_def_id in impl_infos.iter() {
-                self.assemble_inherent_impl_probe(impl_def_id);
-            }
+        let impl_def_ids = ty::queries::inherent_impls::get(self.tcx, self.span, def_id);
+        for &impl_def_id in impl_def_ids.iter() {
+            self.assemble_inherent_impl_probe(impl_def_id);
         }
     }