Auto merge of #41914 - eddyb:region-refactor, r=nikomatsakis

rustc: simpler ParameterEnvironment and free regions.

The commits describe the slow transformation but the highlights are:
* `ReEarlyBound` is considered free, with a scope based on the item that defined the lifetime parameter, and the root body of the `RegionMaps` in use, removing the need for `free_substs`
* `liberate_late_bound_regions` and `implicit_region_bound` moved to typeck
* `CodeExtent` not interned at all now - ideally it would be 2 `u32` but it's small anyway

Future work building up on this could include:
* `ParameterEnvironment` becoming just the result of `predicates_of`
  * interning makes my "parent chain" scheme unnecessary
* `implicit_region_bound` could be retrieved from `RegionMaps`
* renaming `CodeExtent` to `Scope`
  * generalizing "call site" to "use site" or something better to include constants
* renaming `RegionMaps` to `ScopeTree` and its API to talk about "parents" explicitly

src/librustc/cfg/construct.rs

@@ -10,6 +10,7 @@
 
 use rustc_data_structures::graph;
 use cfg::*;
+use middle::region::CodeExtent;
 use ty::{self, TyCtxt};
 use syntax::ast;
 use syntax::ptr::P;
@@ -586,8 +587,8 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                         scope_id: ast::NodeId,
                         to_index: CFGIndex) {
         let mut data = CFGEdgeData { exiting_scopes: vec![] };
-        let mut scope = self.tcx.node_extent(from_expr.id);
-        let target_scope = self.tcx.node_extent(scope_id);
+        let mut scope = CodeExtent::Misc(from_expr.id);
+        let target_scope = CodeExtent::Misc(scope_id);
         let region_maps = self.tcx.region_maps(self.owner_def_id);
         while scope != target_scope {
             data.exiting_scopes.push(scope.node_id());

src/librustc/ich/impls_ty.rs

@@ -39,7 +39,7 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a, 'tcx>> for ty::subst::Kind<'t
     }
 }
 
-impl<'a, 'tcx> HashStable<StableHashingContext<'a, 'tcx>> for ty::RegionKind<'tcx> {
+impl<'a, 'tcx> HashStable<StableHashingContext<'a, 'tcx>> for ty::RegionKind {
     fn hash_stable<W: StableHasherResult>(&self,
                                           hcx: &mut StableHashingContext<'a, 'tcx>,
                                           hasher: &mut StableHasher<W>) {
@@ -54,7 +54,8 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a, 'tcx>> for ty::RegionKind<'tc
                 db.depth.hash_stable(hcx, hasher);
                 i.hash_stable(hcx, hasher);
             }
-            ty::ReEarlyBound(ty::EarlyBoundRegion { index, name }) => {
+            ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, index, name }) => {
+                def_id.hash_stable(hcx, hasher);
                 index.hash_stable(hcx, hasher);
                 name.hash_stable(hcx, hasher);
             }
@@ -409,11 +410,6 @@ impl_stable_hash_for!(enum ::middle::resolve_lifetime::Region {
     Free(call_site_scope_data, decl)
 });
 
-impl_stable_hash_for!(struct ::middle::region::CallSiteScopeData {
-    fn_id,
-    body_id
-});
-
 impl_stable_hash_for!(struct ty::DebruijnIndex {
     depth
 });
@@ -432,25 +428,24 @@ impl_stable_hash_for!(enum ty::cast::CastKind {
     FnPtrAddrCast
 });
 
-impl<'a, 'tcx> HashStable<StableHashingContext<'a, 'tcx>> for ::middle::region::CodeExtentData
+impl<'a, 'tcx> HashStable<StableHashingContext<'a, 'tcx>> for ::middle::region::CodeExtent
 {
     fn hash_stable<W: StableHasherResult>(&self,
                                           hcx: &mut StableHashingContext<'a, 'tcx>,
                                           hasher: &mut StableHasher<W>) {
-        use middle::region::CodeExtentData;
+        use middle::region::CodeExtent;
 
         mem::discriminant(self).hash_stable(hcx, hasher);
         match *self {
-            CodeExtentData::Misc(node_id) |
-            CodeExtentData::DestructionScope(node_id) => {
+            CodeExtent::Misc(node_id) |
+            CodeExtent::DestructionScope(node_id) => {
                 node_id.hash_stable(hcx, hasher);
             }
-            CodeExtentData::CallSiteScope { fn_id, body_id } |
-            CodeExtentData::ParameterScope { fn_id, body_id } => {
-                fn_id.hash_stable(hcx, hasher);
+            CodeExtent::CallSiteScope(body_id) |
+            CodeExtent::ParameterScope(body_id) => {
                 body_id.hash_stable(hcx, hasher);
             }
-            CodeExtentData::Remainder(block_remainder) => {
+            CodeExtent::Remainder(block_remainder) => {
                 block_remainder.hash_stable(hcx, hasher);
             }
         }
@@ -466,7 +461,7 @@ impl_stable_hash_for!(struct ty::adjustment::CoerceUnsizedInfo {
     custom_kind
 });
 
-impl_stable_hash_for!(struct ty::FreeRegion<'tcx> {
+impl_stable_hash_for!(struct ty::FreeRegion {
     scope,
     bound_region
 });

src/librustc/infer/combine.rs

@@ -423,15 +423,6 @@ impl<'cx, 'gcx, 'tcx> TypeRelation<'cx, 'gcx, 'tcx> for Generalizer<'cx, 'gcx, '
                 return Ok(r);
             }
 
-            // Early-bound regions should really have been substituted away before
-            // we get to this point.
-            ty::ReEarlyBound(..) => {
-                span_bug!(
-                    self.span,
-                    "Encountered early bound region when generalizing: {:?}",
-                    r);
-            }
-
             // Always make a fresh region variable for skolemized regions;
             // the higher-ranked decision procedures rely on this.
             ty::ReSkolemized(..) => { }
@@ -442,6 +433,7 @@ impl<'cx, 'gcx, 'tcx> TypeRelation<'cx, 'gcx, 'tcx> for Generalizer<'cx, 'gcx, '
             ty::ReStatic |
             ty::ReScope(..) |
             ty::ReVar(..) |
+            ty::ReEarlyBound(..) |
             ty::ReFree(..) => {
                 match self.ambient_variance {
                     ty::Invariant => return Ok(r),

src/librustc/infer/error_reporting/mod.rs

@@ -151,19 +151,19 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                         return;
                     }
                 };
-                let scope_decorated_tag = match *scope {
-                    region::CodeExtentData::Misc(_) => tag,
-                    region::CodeExtentData::CallSiteScope { .. } => {
+                let scope_decorated_tag = match scope {
+                    region::CodeExtent::Misc(_) => tag,
+                    region::CodeExtent::CallSiteScope(_) => {
                         "scope of call-site for function"
                     }
-                    region::CodeExtentData::ParameterScope { .. } => {
+                    region::CodeExtent::ParameterScope(_) => {
                         "scope of function body"
                     }
-                    region::CodeExtentData::DestructionScope(_) => {
+                    region::CodeExtent::DestructionScope(_) => {
                         new_string = format!("destruction scope surrounding {}", tag);
                         &new_string[..]
                     }
-                    region::CodeExtentData::Remainder(r) => {
+                    region::CodeExtent::Remainder(r) => {
                         new_string = format!("block suffix following statement {}",
                                              r.first_statement_index);
                         &new_string[..]
@@ -172,19 +172,35 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 explain_span(self, scope_decorated_tag, span)
             }
 
-            ty::ReFree(ref fr) => {
-                let prefix = match fr.bound_region {
-                    ty::BrAnon(idx) => {
-                        format!("the anonymous lifetime #{} defined on", idx + 1)
+            ty::ReEarlyBound(_) |
+            ty::ReFree(_) => {
+                let scope = match *region {
+                    ty::ReEarlyBound(ref br) => {
+                        self.parent_def_id(br.def_id).unwrap()
                     }
-                    ty::BrFresh(_) => "an anonymous lifetime defined on".to_owned(),
-                    _ => {
-                        format!("the lifetime {} as defined on",
-                                fr.bound_region)
+                    ty::ReFree(ref fr) => fr.scope,
+                    _ => bug!()
+                };
+                let prefix = match *region {
+                    ty::ReEarlyBound(ref br) => {
+                        format!("the lifetime {} as defined on", br.name)
+                    }
+                    ty::ReFree(ref fr) => {
+                        match fr.bound_region {
+                            ty::BrAnon(idx) => {
+                                format!("the anonymous lifetime #{} defined on", idx + 1)
+                            }
+                            ty::BrFresh(_) => "an anonymous lifetime defined on".to_owned(),
+                            _ => {
+                                format!("the lifetime {} as defined on",
+                                        fr.bound_region)
+                            }
+                        }
                     }
+                    _ => bug!()
                 };
 
-                let node = fr.scope.map(|s| s.node_id())
+                let node = self.hir.as_local_node_id(scope)
                                    .unwrap_or(DUMMY_NODE_ID);
                 let unknown;
                 let tag = match self.hir.find(node) {
@@ -199,12 +215,12 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                     Some(_) => {
                         unknown = format!("unexpected node ({}) for scope {:?}.  \
                                            Please report a bug.",
-                                          self.hir.node_to_string(node), fr.scope);
+                                          self.hir.node_to_string(node), scope);
                         &unknown
                     }
                     None => {
                         unknown = format!("unknown node for scope {:?}.  \
-                                           Please report a bug.", fr.scope);
+                                           Please report a bug.", scope);
                         &unknown
                     }
                 };
@@ -216,8 +232,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 
             ty::ReEmpty => ("the empty lifetime".to_owned(), None),
 
-            ty::ReEarlyBound(ref data) => (data.name.to_string(), None),
-
             // FIXME(#13998) ReSkolemized should probably print like
             // ReFree rather than dumping Debug output on the user.
             //
@@ -797,6 +811,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         }
 
         let mut err = match *sub {
+            ty::ReEarlyBound(_) |
             ty::ReFree(ty::FreeRegion {bound_region: ty::BrNamed(..), ..}) => {
                 // Does the required lifetime have a nice name we can print?
                 let mut err = struct_span_err!(self.tcx.sess,

src/librustc/infer/freshen.rs

@@ -85,13 +85,13 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
         match *r {
-            ty::ReEarlyBound(..) |
             ty::ReLateBound(..) => {
                 // leave bound regions alone
                 r
             }
 
             ty::ReStatic |
+            ty::ReEarlyBound(..) |
             ty::ReFree(_) |
             ty::ReScope(_) |
             ty::ReVar(_) |

src/librustc/infer/higher_ranked/mod.rs

@@ -274,7 +274,7 @@ impl<'a, 'gcx, 'tcx> CombineFields<'a, 'gcx, 'tcx> {
                                              -> ty::Region<'tcx> {
             // Regions that pre-dated the LUB computation stay as they are.
             if !is_var_in_set(new_vars, r0) {
-                assert!(!r0.is_bound());
+                assert!(!r0.is_late_bound());
                 debug!("generalize_region(r0={:?}): not new variable", r0);
                 return r0;
             }
@@ -288,7 +288,7 @@ impl<'a, 'gcx, 'tcx> CombineFields<'a, 'gcx, 'tcx> {
                 debug!("generalize_region(r0={:?}): \
                         non-new-variables found in {:?}",
                        r0, tainted);
-                assert!(!r0.is_bound());
+                assert!(!r0.is_late_bound());
                 return r0;
             }
 
@@ -371,7 +371,7 @@ impl<'a, 'gcx, 'tcx> CombineFields<'a, 'gcx, 'tcx> {
                                              r0: ty::Region<'tcx>)
                                              -> ty::Region<'tcx> {
             if !is_var_in_set(new_vars, r0) {
-                assert!(!r0.is_bound());
+                assert!(!r0.is_late_bound());
                 return r0;
             }
 
@@ -424,7 +424,7 @@ impl<'a, 'gcx, 'tcx> CombineFields<'a, 'gcx, 'tcx> {
                 return rev_lookup(infcx, span, a_map, a_r.unwrap());
             } else if a_r.is_none() && b_r.is_none() {
                 // Not related to bound variables from either fn:
-                assert!(!r0.is_bound());
+                assert!(!r0.is_late_bound());
                 return r0;
             } else {
                 // Other:

src/librustc/infer/mod.rs

@@ -450,10 +450,10 @@ impl<'a, 'tcx> InferEnv<'a, 'tcx> for hir::BodyId {
                 -> (Option<&'a ty::TypeckTables<'tcx>>,
                     Option<ty::TypeckTables<'tcx>>,
                     Option<ty::ParameterEnvironment<'tcx>>) {
-        let item_id = tcx.hir.body_owner(self);
-        (Some(tcx.typeck_tables_of(tcx.hir.local_def_id(item_id))),
+        let def_id = tcx.hir.body_owner_def_id(self);
+        (Some(tcx.typeck_tables_of(def_id)),
          None,
-         Some(ty::ParameterEnvironment::for_item(tcx, item_id)))
+         Some(tcx.parameter_environment(def_id)))
     }
 }
 
@@ -1009,7 +1009,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     }
 
     pub fn add_given(&self,
-                     sub: ty::FreeRegion<'tcx>,
+                     sub: ty::Region<'tcx>,
                      sup: ty::RegionVid)
     {
         self.region_vars.add_given(sub, sup);
@@ -1324,7 +1324,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
     pub fn resolve_regions_and_report_errors(&self,
                                              region_context: DefId,
-                                             region_map: &RegionMaps<'tcx>,
+                                             region_map: &RegionMaps,
                                              free_regions: &FreeRegionMap<'tcx>) {
         let region_rels = RegionRelations::new(self.tcx,
                                                region_context,

src/librustc/infer/region_inference/graphviz.rs

@@ -124,20 +124,20 @@ struct ConstraintGraph<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     graph_name: String,
     region_rels: &'a RegionRelations<'a, 'gcx, 'tcx>,
     map: &'a FxHashMap<Constraint<'tcx>, SubregionOrigin<'tcx>>,
-    node_ids: FxHashMap<Node<'tcx>, usize>,
+    node_ids: FxHashMap<Node, usize>,
 }
 
 #[derive(Clone, Hash, PartialEq, Eq, Debug, Copy)]
-enum Node<'tcx> {
+enum Node {
     RegionVid(ty::RegionVid),
-    Region(ty::RegionKind<'tcx>),
+    Region(ty::RegionKind),
 }
 
 // type Edge = Constraint;
 #[derive(Clone, PartialEq, Eq, Debug, Copy)]
 enum Edge<'tcx> {
     Constraint(Constraint<'tcx>),
-    EnclScope(CodeExtent<'tcx>, CodeExtent<'tcx>),
+    EnclScope(CodeExtent, CodeExtent),
 }
 
 impl<'a, 'gcx, 'tcx> ConstraintGraph<'a, 'gcx, 'tcx> {
@@ -176,7 +176,7 @@ impl<'a, 'gcx, 'tcx> ConstraintGraph<'a, 'gcx, 'tcx> {
 }
 
 impl<'a, 'gcx, 'tcx> dot::Labeller<'a> for ConstraintGraph<'a, 'gcx, 'tcx> {
-    type Node = Node<'tcx>;
+    type Node = Node;
     type Edge = Edge<'tcx>;
     fn graph_id(&self) -> dot::Id {
         dot::Id::new(&*self.graph_name).unwrap()
@@ -209,7 +209,7 @@ impl<'a, 'gcx, 'tcx> dot::Labeller<'a> for ConstraintGraph<'a, 'gcx, 'tcx> {
     }
 }
 
-fn constraint_to_nodes<'tcx>(c: &Constraint<'tcx>) -> (Node<'tcx>, Node<'tcx>) {
+fn constraint_to_nodes(c: &Constraint) -> (Node, Node) {
     match *c {
         Constraint::ConstrainVarSubVar(rv_1, rv_2) =>
             (Node::RegionVid(rv_1), Node::RegionVid(rv_2)),
@@ -222,7 +222,7 @@ fn constraint_to_nodes<'tcx>(c: &Constraint<'tcx>) -> (Node<'tcx>, Node<'tcx>) {
     }
 }
 
-fn edge_to_nodes<'tcx>(e: &Edge<'tcx>) -> (Node<'tcx>, Node<'tcx>) {
+fn edge_to_nodes(e: &Edge) -> (Node, Node) {
     match *e {
         Edge::Constraint(ref c) => constraint_to_nodes(c),
         Edge::EnclScope(sub, sup) => {
@@ -233,9 +233,9 @@ fn edge_to_nodes<'tcx>(e: &Edge<'tcx>) -> (Node<'tcx>, Node<'tcx>) {
 }
 
 impl<'a, 'gcx, 'tcx> dot::GraphWalk<'a> for ConstraintGraph<'a, 'gcx, 'tcx> {
-    type Node = Node<'tcx>;
+    type Node = Node;
     type Edge = Edge<'tcx>;
-    fn nodes(&self) -> dot::Nodes<Node<'tcx>> {
+    fn nodes(&self) -> dot::Nodes<Node> {
         let mut set = FxHashSet();
         for node in self.node_ids.keys() {
             set.insert(*node);
@@ -250,12 +250,12 @@ impl<'a, 'gcx, 'tcx> dot::GraphWalk<'a> for ConstraintGraph<'a, 'gcx, 'tcx> {
         debug!("region graph has {} edges", v.len());
         Cow::Owned(v)
     }
-    fn source(&self, edge: &Edge<'tcx>) -> Node<'tcx> {
+    fn source(&self, edge: &Edge<'tcx>) -> Node {
         let (n1, _) = edge_to_nodes(edge);
         debug!("edge {:?} has source {:?}", edge, n1);
         n1
     }
-    fn target(&self, edge: &Edge<'tcx>) -> Node<'tcx> {
+    fn target(&self, edge: &Edge<'tcx>) -> Node {
         let (_, n2) = edge_to_nodes(edge);
         debug!("edge {:?} has target {:?}", edge, n2);
         n2