Rollup merge of rust-lang#41534 - achernyak:master, r=eddyb

query for describe_def

Resolves `fn describe_def(&self, def: DefId) -> Option<Def>;` of rust-lang#41417.

r? @nikomatsakis I would greatly appreciate a review. I hope I covered everything described in the pr.

Author: frewsxcv

src/librustc/middle/cstore.rs

@@ -22,7 +22,7 @@
 // are *mostly* used as a part of that interface, but these should
 // probably get a better home if someone can find one.
 
-use hir::def::{self, Def};
+use hir::def;
 use hir::def_id::{CrateNum, DefId, DefIndex};
 use hir::map as hir_map;
 use hir::map::definitions::{Definitions, DefKey, DisambiguatedDefPathData};
@@ -181,7 +181,6 @@ pub trait CrateStore {
     fn crate_data_as_rc_any(&self, krate: CrateNum) -> Rc<Any>;
 
     // item info
-    fn describe_def(&self, def: DefId) -> Option<Def>;
     fn def_span(&self, sess: &Session, def: DefId) -> Span;
     fn stability(&self, def: DefId) -> Option<attr::Stability>;
     fn deprecation(&self, def: DefId) -> Option<attr::Deprecation>;
@@ -313,7 +312,6 @@ impl CrateStore for DummyCrateStore {
     fn crate_data_as_rc_any(&self, krate: CrateNum) -> Rc<Any>
         { bug!("crate_data_as_rc_any") }
     // item info
-    fn describe_def(&self, def: DefId) -> Option<Def> { bug!("describe_def") }
     fn def_span(&self, sess: &Session, def: DefId) -> Span { bug!("def_span") }
     fn stability(&self, def: DefId) -> Option<attr::Stability> { bug!("stability") }
     fn deprecation(&self, def: DefId) -> Option<attr::Deprecation> { bug!("deprecation") }

src/librustc/middle/stability.rs

@@ -432,7 +432,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     // (See issue #38412)
     fn skip_stability_check_due_to_privacy(self, mut def_id: DefId) -> bool {
         // Check if `def_id` is a trait method.
-        match self.sess.cstore.describe_def(def_id) {
+        match self.describe_def(def_id) {
             Some(Def::Method(_)) |
             Some(Def::AssociatedTy(_)) |
             Some(Def::AssociatedConst(_)) => {

src/librustc/ty/maps.rs

@@ -10,6 +10,7 @@
 
 use dep_graph::{DepGraph, DepNode, DepTrackingMap, DepTrackingMapConfig};
 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
+use hir::def::Def;
 use hir;
 use middle::const_val;
 use middle::privacy::AccessLevels;
@@ -264,6 +265,12 @@ impl<'tcx> QueryDescription for queries::symbol_name<'tcx> {
     }
 }
 
+impl<'tcx> QueryDescription for queries::describe_def<'tcx> {
+    fn describe(_: TyCtxt, _: DefId) -> String {
+        bug!("describe_def")
+    }
+}
+
 macro_rules! define_maps {
     (<$tcx:tt>
      $($(#[$attr:meta])*
@@ -538,7 +545,9 @@ define_maps! { <'tcx>
     pub mir_shims: mir_shim_dep_node(ty::InstanceDef<'tcx>) -> &'tcx RefCell<mir::Mir<'tcx>>,
 
     pub def_symbol_name: SymbolName(DefId) -> ty::SymbolName,
-    pub symbol_name: symbol_name_dep_node(ty::Instance<'tcx>) -> ty::SymbolName
+    pub symbol_name: symbol_name_dep_node(ty::Instance<'tcx>) -> ty::SymbolName,
+
+    pub describe_def: meta_data_node(DefId) -> Option<Def>
 }
 
 fn coherent_trait_dep_node((_, def_id): (CrateNum, DefId)) -> DepNode<DefId> {
@@ -570,3 +579,7 @@ fn typeck_item_bodies_dep_node(_: CrateNum) -> DepNode<DefId> {
 fn const_eval_dep_node((def_id, _): (DefId, &Substs)) -> DepNode<DefId> {
     DepNode::ConstEval(def_id)
 }
+
+fn meta_data_node(def_id: DefId) -> DepNode<DefId> {
+    DepNode::MetaData(def_id)
+}

src/librustc/ty/mod.rs

@@ -2385,7 +2385,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// ID of the impl that the method belongs to. Otherwise, return `None`.
     pub fn impl_of_method(self, def_id: DefId) -> Option<DefId> {
         let item = if def_id.krate != LOCAL_CRATE {
-            if let Some(Def::Method(_)) = self.sess.cstore.describe_def(def_id) {
+            if let Some(Def::Method(_)) = self.describe_def(def_id) {
                 Some(self.associated_item(def_id))
             } else {
                 None

src/librustc_const_eval/eval.rs

@@ -68,7 +68,7 @@ pub fn lookup_const_by_id<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             _ => Some((def_id, substs))
         }
     } else {
-        match tcx.sess.cstore.describe_def(def_id) {
+        match tcx.describe_def(def_id) {
             Some(Def::AssociatedConst(_)) => {
                 // As mentioned in the comments above for in-crate
                 // constants, we only try to find the expression for a

src/librustc_metadata/cstore_impl.rs

@@ -17,7 +17,7 @@ use rustc::dep_graph::DepTrackingMapConfig;
 use rustc::middle::cstore::{CrateStore, CrateSource, LibSource, DepKind,
                             ExternCrate, NativeLibrary, LinkMeta,
                             LinkagePreference, LoadedMacro, EncodedMetadata};
-use rustc::hir::def::{self, Def};
+use rustc::hir::def;
 use rustc::middle::lang_items;
 use rustc::session::Session;
 use rustc::ty::{self, TyCtxt};
@@ -113,18 +113,14 @@ provide! { <'tcx> tcx, def_id, cdata
     closure_type => { cdata.closure_ty(def_id.index, tcx) }
     inherent_impls => { Rc::new(cdata.get_inherent_implementations_for_type(def_id.index)) }
     is_foreign_item => { cdata.is_foreign_item(def_id.index) }
+    describe_def => { cdata.get_def(def_id.index) }
 }
 
 impl CrateStore for cstore::CStore {
     fn crate_data_as_rc_any(&self, krate: CrateNum) -> Rc<Any> {
         self.get_crate_data(krate)
     }
 
-    fn describe_def(&self, def: DefId) -> Option<Def> {
-        self.dep_graph.read(DepNode::MetaData(def));
-        self.get_crate_data(def.krate).get_def(def.index)
-    }
-
     fn def_span(&self, sess: &Session, def: DefId) -> Span {
         self.dep_graph.read(DepNode::MetaData(def));
         self.get_crate_data(def.krate).get_span(def.index, sess)