Rollup merge of rust-lang#37402 - eddyb:lazy-3, r=nikomatsakis

[3/n] rustc: unify and simplify managing associated items.

_This is part of a series ([prev](rust-lang#37401) | [next](rust-lang#37404)) of patches designed to rework rustc into an out-of-order on-demand pipeline model for both better feature support (e.g. [MIR-based](https://github.com/solson/miri) early constant evaluation) and incremental execution of compiler passes (e.g. type-checking), with beneficial consequences to IDE support as well.
If any motivation is unclear, please ask for additional PR description clarifications or code comments._

<hr>

`ImplOrTraitItem`/`impl_or_trait_item` have been renamed to `AssociatedItem`/`associated_item`.

The common fields from (what used to be) `ty::ImplOrTraitItem`'s variants have been pulled out, leaving only an `AssociatedKind` C-like enum to distinguish between methods, constants and types.

The type information has been removed from `AssociatedItem`, and as such the latter can now be computed on-demand from the local HIR map, i.e. an extern-crate-enabled `TraitItem | ImplItem`.
It may be moved to HIR in the future, if we intend to start using HIR types cross-crate.

`ty::ExplicitSelfCategory` has been moved to `rustc_typeck` and is produced on-demand from the signature of the method, and a `method_has_self_argument` field on `AssociatedItem`, which is used to indicate that the first argument is a sugary "method receiver" and as such, method call syntax can be used.

src/librustc/dep_graph/dep_node.rs

@@ -103,11 +103,11 @@ pub enum DepNode<D: Clone + Debug> {
     // nodes. Often we map multiple tables to the same node if there
     // is no point in distinguishing them (e.g., both the type and
     // predicates for an item wind up in `ItemSignature`).
-    ImplOrTraitItems(D),
+    AssociatedItems(D),
     ItemSignature(D),
     FieldTy(D),
     SizedConstraint(D),
-    ImplOrTraitItemDefIds(D),
+    AssociatedItemDefIds(D),
     InherentImpls(D),
 
     // The set of impls for a given trait. Ultimately, it would be
@@ -153,10 +153,10 @@ impl<D: Clone + Debug> DepNode<D> {
             TransCrateItem,
             TypeckItemType,
             TypeckItemBody,
-            ImplOrTraitItems,
+            AssociatedItems,
             ItemSignature,
             FieldTy,
-            ImplOrTraitItemDefIds,
+            AssociatedItemDefIds,
             InherentImpls,
             TraitImpls,
             ReprHints,
@@ -219,11 +219,11 @@ impl<D: Clone + Debug> DepNode<D> {
             RvalueCheck(ref d) => op(d).map(RvalueCheck),
             TransCrateItem(ref d) => op(d).map(TransCrateItem),
             TransInlinedItem(ref d) => op(d).map(TransInlinedItem),
-            ImplOrTraitItems(ref d) => op(d).map(ImplOrTraitItems),
+            AssociatedItems(ref d) => op(d).map(AssociatedItems),
             ItemSignature(ref d) => op(d).map(ItemSignature),
             FieldTy(ref d) => op(d).map(FieldTy),
             SizedConstraint(ref d) => op(d).map(SizedConstraint),
-            ImplOrTraitItemDefIds(ref d) => op(d).map(ImplOrTraitItemDefIds),
+            AssociatedItemDefIds(ref d) => op(d).map(AssociatedItemDefIds),
             InherentImpls(ref d) => op(d).map(InherentImpls),
             TraitImpls(ref d) => op(d).map(TraitImpls),
             TraitItems(ref d) => op(d).map(TraitItems),

src/librustc/middle/cstore.rs

@@ -147,7 +147,7 @@ pub trait CrateStore<'tcx> {
     fn implementations_of_trait(&self, filter: Option<DefId>) -> Vec<DefId>;
 
     // impl info
-    fn impl_or_trait_items(&self, def_id: DefId) -> Vec<DefId>;
+    fn associated_item_def_ids(&self, def_id: DefId) -> Vec<DefId>;
     fn impl_trait_ref<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                           -> Option<ty::TraitRef<'tcx>>;
     fn impl_polarity(&self, def: DefId) -> hir::ImplPolarity;
@@ -157,8 +157,8 @@ pub trait CrateStore<'tcx> {
 
     // trait/impl-item info
     fn trait_of_item(&self, def_id: DefId) -> Option<DefId>;
-    fn impl_or_trait_item<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
-                              -> Option<ty::ImplOrTraitItem<'tcx>>;
+    fn associated_item<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
+                           -> Option<ty::AssociatedItem>;
 
     // flags
     fn is_const_fn(&self, did: DefId) -> bool;
@@ -311,8 +311,8 @@ impl<'tcx> CrateStore<'tcx> for DummyCrateStore {
     }
 
     // impl info
-    fn impl_or_trait_items(&self, def_id: DefId) -> Vec<DefId>
-        { bug!("impl_or_trait_items") }
+    fn associated_item_def_ids(&self, def_id: DefId) -> Vec<DefId>
+        { bug!("associated_items") }
     fn impl_trait_ref<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                           -> Option<ty::TraitRef<'tcx>> { bug!("impl_trait_ref") }
     fn impl_polarity(&self, def: DefId) -> hir::ImplPolarity { bug!("impl_polarity") }
@@ -323,8 +323,8 @@ impl<'tcx> CrateStore<'tcx> for DummyCrateStore {
 
     // trait/impl-item info
     fn trait_of_item(&self, def_id: DefId) -> Option<DefId> { bug!("trait_of_item") }
-    fn impl_or_trait_item<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
-                              -> Option<ty::ImplOrTraitItem<'tcx>> { bug!("impl_or_trait_item") }
+    fn associated_item<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
+                           -> Option<ty::AssociatedItem> { bug!("associated_item") }
 
     // flags
     fn is_const_fn(&self, did: DefId) -> bool { bug!("is_const_fn") }

src/librustc/middle/dead.rs

@@ -471,11 +471,10 @@ impl<'a, 'tcx> DeadVisitor<'a, 'tcx> {
         // This is done to handle the case where, for example, the static
         // method of a private type is used, but the type itself is never
         // called directly.
-        let impl_items = self.tcx.impl_or_trait_item_def_ids.borrow();
         if let Some(impl_list) =
                 self.tcx.inherent_impls.borrow().get(&self.tcx.map.local_def_id(id)) {
-            for impl_did in impl_list.iter() {
-                for &item_did in &impl_items[impl_did][..] {
+            for &impl_did in impl_list.iter() {
+                for &item_did in &self.tcx.associated_item_def_ids(impl_did)[..] {
                     if let Some(item_node_id) = self.tcx.map.as_local_node_id(item_did) {
                         if self.live_symbols.contains(&item_node_id) {
                             return true;

src/librustc/middle/expr_use_visitor.rs

@@ -227,8 +227,8 @@ impl OverloadedCallType {
     }
 
     fn from_method_id(tcx: TyCtxt, method_id: DefId) -> OverloadedCallType {
-        let method = tcx.impl_or_trait_item(method_id);
-        OverloadedCallType::from_trait_id(tcx, method.container().id())
+        let method = tcx.associated_item(method_id);
+        OverloadedCallType::from_trait_id(tcx, method.container.id())
     }
 }
 

src/librustc/middle/stability.rs

@@ -529,14 +529,11 @@ pub fn check_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         // items.
         hir::ItemImpl(.., Some(ref t), _, ref impl_items) => {
             let trait_did = tcx.expect_def(t.ref_id).def_id();
-            let trait_items = tcx.trait_items(trait_did);
-
             for impl_item in impl_items {
-                let item = trait_items.iter().find(|item| {
-                    item.name() == impl_item.name
-                }).unwrap();
+                let item = tcx.associated_items(trait_did)
+                    .find(|item| item.name == impl_item.name).unwrap();
                 if warn_about_defns {
-                    maybe_do_stability_check(tcx, item.def_id(), impl_item.span, cb);
+                    maybe_do_stability_check(tcx, item.def_id, impl_item.span, cb);
                 }
             }
         }
@@ -685,15 +682,8 @@ fn is_internal<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, span: Span) -> bool {
 }
 
 fn is_staged_api<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, id: DefId) -> bool {
-    match tcx.trait_item_of_item(id) {
-        Some(trait_method_id) if trait_method_id != id => {
-            is_staged_api(tcx, trait_method_id)
-        }
-        _ => {
-            *tcx.stability.borrow_mut().staged_api.entry(id.krate).or_insert_with(
-                || tcx.sess.cstore.is_staged_api(id.krate))
-        }
-    }
+    *tcx.stability.borrow_mut().staged_api.entry(id.krate).or_insert_with(
+        || tcx.sess.cstore.is_staged_api(id.krate))
 }
 
 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {

src/librustc/traits/error_reporting.rs

@@ -617,25 +617,23 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                          in the supertrait listing"
                 }
 
-                ObjectSafetyViolation::Method(method,
+                ObjectSafetyViolation::Method(name,
                                               MethodViolationCode::StaticMethod) => {
-                    buf = format!("method `{}` has no receiver",
-                                  method.name);
+                    buf = format!("method `{}` has no receiver", name);
                     &buf
                 }
 
-                ObjectSafetyViolation::Method(method,
+                ObjectSafetyViolation::Method(name,
                                               MethodViolationCode::ReferencesSelf) => {
                     buf = format!("method `{}` references the `Self` type \
                                        in its arguments or return type",
-                                  method.name);
+                                  name);
                     &buf
                 }
 
-                ObjectSafetyViolation::Method(method,
+                ObjectSafetyViolation::Method(name,
                                               MethodViolationCode::Generic) => {
-                    buf = format!("method `{}` has generic type parameters",
-                                  method.name);
+                    buf = format!("method `{}` has generic type parameters", name);
                     &buf
                 }
             };

src/librustc/traits/mod.rs

@@ -569,18 +569,14 @@ pub fn get_vtable_methods<'a, 'tcx>(
     supertraits(tcx, trait_ref).flat_map(move |trait_ref| {
         tcx.populate_implementations_for_trait_if_necessary(trait_ref.def_id());
 
-        let trait_item_def_ids = tcx.impl_or_trait_items(trait_ref.def_id());
-        let trait_methods = (0..trait_item_def_ids.len()).filter_map(move |i| {
-            match tcx.impl_or_trait_item(trait_item_def_ids[i]) {
-                ty::MethodTraitItem(m) => Some(m),
-                _ => None
-            }
-        });
+        let trait_methods = tcx.associated_items(trait_ref.def_id())
+            .filter(|item| item.kind == ty::AssociatedKind::Method);
 
         // Now list each method's DefId and Substs (for within its trait).
         // If the method can never be called from this object, produce None.
         trait_methods.map(move |trait_method| {
             debug!("get_vtable_methods: trait_method={:?}", trait_method);
+            let def_id = trait_method.def_id;
 
             // Some methods cannot be called on an object; skip those.
             if !tcx.is_vtable_safe_method(trait_ref.def_id(), &trait_method) {
@@ -590,21 +586,21 @@ pub fn get_vtable_methods<'a, 'tcx>(
 
             // the method may have some early-bound lifetimes, add
             // regions for those
-            let substs = Substs::for_item(tcx, trait_method.def_id,
-                                            |_, _| tcx.mk_region(ty::ReErased),
-                                            |def, _| trait_ref.substs().type_for_def(def));
+            let substs = Substs::for_item(tcx, def_id,
+                                          |_, _| tcx.mk_region(ty::ReErased),
+                                          |def, _| trait_ref.substs().type_for_def(def));
 
             // It's possible that the method relies on where clauses that
             // do not hold for this particular set of type parameters.
             // Note that this method could then never be called, so we
             // do not want to try and trans it, in that case (see #23435).
-            let predicates = trait_method.predicates.instantiate_own(tcx, substs);
+            let predicates = tcx.lookup_predicates(def_id).instantiate_own(tcx, substs);
             if !normalize_and_test_predicates(tcx, predicates.predicates) {
                 debug!("get_vtable_methods: predicates do not hold");
                 return None;
             }
 
-            Some((trait_method.def_id, substs))
+            Some((def_id, substs))
         })
     })
 }

src/librustc/traits/object_safety.rs

@@ -22,11 +22,10 @@ use super::elaborate_predicates;
 use hir::def_id::DefId;
 use traits;
 use ty::{self, ToPolyTraitRef, Ty, TyCtxt, TypeFoldable};
-use std::rc::Rc;
 use syntax::ast;
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
-pub enum ObjectSafetyViolation<'tcx> {
+pub enum ObjectSafetyViolation {
     /// Self : Sized declared on the trait
     SizedSelf,
 
@@ -35,7 +34,7 @@ pub enum ObjectSafetyViolation<'tcx> {
     SupertraitSelf,
 
     /// Method has something illegal
-    Method(Rc<ty::Method<'tcx>>, MethodViolationCode),
+    Method(ast::Name, MethodViolationCode),
 }
 
 /// Reasons a method might not be object-safe.
@@ -77,7 +76,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// because `object_safety_violations` can't be used during
     /// type collection.
     pub fn astconv_object_safety_violations(self, trait_def_id: DefId)
-                                            -> Vec<ObjectSafetyViolation<'tcx>>
+                                            -> Vec<ObjectSafetyViolation>
     {
         let mut violations = vec![];
 
@@ -93,29 +92,23 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     }
 
     pub fn object_safety_violations(self, trait_def_id: DefId)
-                                    -> Vec<ObjectSafetyViolation<'tcx>>
+                                    -> Vec<ObjectSafetyViolation>
     {
         traits::supertrait_def_ids(self, trait_def_id)
             .flat_map(|def_id| self.object_safety_violations_for_trait(def_id))
             .collect()
     }
 
     fn object_safety_violations_for_trait(self, trait_def_id: DefId)
-                                          -> Vec<ObjectSafetyViolation<'tcx>>
+                                          -> Vec<ObjectSafetyViolation>
     {
         // Check methods for violations.
-        let mut violations: Vec<_> =
-            self.trait_items(trait_def_id).iter()
+        let mut violations: Vec<_> = self.associated_items(trait_def_id)
+            .filter(|item| item.kind == ty::AssociatedKind::Method)
             .filter_map(|item| {
-                match *item {
-                    ty::MethodTraitItem(ref m) => {
-                        self.object_safety_violation_for_method(trait_def_id, &m)
-                            .map(|code| ObjectSafetyViolation::Method(m.clone(), code))
-                    }
-                    _ => None,
-                }
-            })
-            .collect();
+                self.object_safety_violation_for_method(trait_def_id, &item)
+                    .map(|code| ObjectSafetyViolation::Method(item.name, code))
+            }).collect();
 
         // Check the trait itself.
         if self.trait_has_sized_self(trait_def_id) {
@@ -198,7 +191,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// Returns `Some(_)` if this method makes the containing trait not object safe.
     fn object_safety_violation_for_method(self,
                                           trait_def_id: DefId,
-                                          method: &ty::Method<'gcx>)
+                                          method: &ty::AssociatedItem)
                                           -> Option<MethodViolationCode>
     {
         // Any method that has a `Self : Sized` requisite is otherwise
@@ -216,7 +209,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// otherwise ensure that they cannot be used when `Self=Trait`.
     pub fn is_vtable_safe_method(self,
                                  trait_def_id: DefId,
-                                 method: &ty::Method<'gcx>)
+                                 method: &ty::AssociatedItem)
                                  -> bool
     {
         // Any method that has a `Self : Sized` requisite can't be called.
@@ -233,26 +226,19 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// `Self:Sized`.
     fn virtual_call_violation_for_method(self,
                                          trait_def_id: DefId,
-                                         method: &ty::Method<'tcx>)
+                                         method: &ty::AssociatedItem)
                                          -> Option<MethodViolationCode>
     {
         // The method's first parameter must be something that derefs (or
         // autorefs) to `&self`. For now, we only accept `self`, `&self`
         // and `Box<Self>`.
-        match method.explicit_self {
-            ty::ExplicitSelfCategory::Static => {
-                return Some(MethodViolationCode::StaticMethod);
-            }
-
-            ty::ExplicitSelfCategory::ByValue |
-            ty::ExplicitSelfCategory::ByReference(..) |
-            ty::ExplicitSelfCategory::ByBox => {
-            }
+        if !method.method_has_self_argument {
+            return Some(MethodViolationCode::StaticMethod);
         }
 
         // The `Self` type is erased, so it should not appear in list of
         // arguments or return type apart from the receiver.
-        let ref sig = method.fty.sig;
+        let ref sig = self.lookup_item_type(method.def_id).ty.fn_sig();
         for &input_ty in &sig.0.inputs[1..] {
             if self.contains_illegal_self_type_reference(trait_def_id, input_ty) {
                 return Some(MethodViolationCode::ReferencesSelf);
@@ -263,7 +249,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         }
 
         // We can't monomorphize things like `fn foo<A>(...)`.
-        if !method.generics.types.is_empty() {
+        if !self.lookup_generics(method.def_id).types.is_empty() {
             return Some(MethodViolationCode::Generic);
         }