Auto merge of #38813 - eddyb:lazy-11, r=nikomatsakis

[11/n] Separate ty::Tables into one per each body.

_This is part of a series ([prev](#38449) | [next]()) 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>

In order to track the results of type-checking and inference for incremental recompilation, they must be stored separately for each function or constant value, instead of lumped together.

These side-`Tables` also have to be tracked by various passes, as they visit through bodies (all of which have `Tables`, even if closures share the ones from their parent functions). This is usually done by switching a `tables` field in an override of `visit_nested_body` before recursing through `visit_body`, to the relevant one and then restoring it - however, in many cases the nesting is unnecessary and creating the visitor for each body in the crate and then visiting that body, would be a much cleaner solution.

To simplify handling of inlined HIR & its side-tables, their `NodeId` remapping and entries HIR map were fully stripped out, which means that `NodeId`s from inlined HIR must not be used where a local `NodeId` is expected. It might be possible to make the nodes (`Expr`, `Block`, `Pat`, etc.) that only show up within a `Body` have IDs that are scoped to that `Body`, which would also allow `Tables` to use `Vec`s.

That last part also fixes #38790 which was accidentally introduced in a previous refactor.

src/librustc/cfg/construct.rs

@@ -18,6 +18,7 @@ use hir::{self, PatKind};
 
 struct CFGBuilder<'a, 'tcx: 'a> {
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    tables: &'a ty::Tables<'tcx>,
     graph: CFGGraph,
     fn_exit: CFGIndex,
     loop_scopes: Vec<LoopScope>,
@@ -42,10 +43,23 @@ pub fn construct<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let fn_exit = graph.add_node(CFGNodeData::Exit);
     let body_exit;
 
+    // Find the function this expression is from.
+    let mut node_id = body.id;
+    loop {
+        let node = tcx.map.get(node_id);
+        if hir::map::blocks::FnLikeNode::from_node(node).is_some() {
+            break;
+        }
+        let parent = tcx.map.get_parent_node(node_id);
+        assert!(node_id != parent);
+        node_id = parent;
+    }
+
     let mut cfg_builder = CFGBuilder {
+        tcx: tcx,
+        tables: tcx.item_tables(tcx.map.local_def_id(node_id)),
         graph: graph,
         fn_exit: fn_exit,
-        tcx: tcx,
         loop_scopes: Vec::new()
     };
     body_exit = cfg_builder.expr(body, entry);
@@ -310,11 +324,11 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
             }
 
             hir::ExprIndex(ref l, ref r) |
-            hir::ExprBinary(_, ref l, ref r) if self.tcx.tables().is_method_call(expr.id) => {
+            hir::ExprBinary(_, ref l, ref r) if self.tables.is_method_call(expr.id) => {
                 self.call(expr, pred, &l, Some(&**r).into_iter())
             }
 
-            hir::ExprUnary(_, ref e) if self.tcx.tables().is_method_call(expr.id) => {
+            hir::ExprUnary(_, ref e) if self.tables.is_method_call(expr.id) => {
                 self.call(expr, pred, &e, None::<hir::Expr>.iter())
             }
 
@@ -368,9 +382,9 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
             func_or_rcvr: &hir::Expr,
             args: I) -> CFGIndex {
         let method_call = ty::MethodCall::expr(call_expr.id);
-        let fn_ty = match self.tcx.tables().method_map.get(&method_call) {
+        let fn_ty = match self.tables.method_map.get(&method_call) {
             Some(method) => method.ty,
-            None => self.tcx.tables().expr_ty_adjusted(func_or_rcvr)
+            None => self.tables.expr_ty_adjusted(func_or_rcvr)
         };
 
         let func_or_rcvr_exit = self.expr(func_or_rcvr, pred);

src/librustc/dep_graph/dep_node.rs

@@ -113,6 +113,7 @@ pub enum DepNode<D: Clone + Debug> {
     SizedConstraint(D),
     AssociatedItemDefIds(D),
     InherentImpls(D),
+    Tables(D),
 
     // The set of impls for a given trait. Ultimately, it would be
     // nice to get more fine-grained here (e.g., to include a
@@ -162,6 +163,7 @@ impl<D: Clone + Debug> DepNode<D> {
             ItemSignature,
             AssociatedItemDefIds,
             InherentImpls,
+            Tables,
             TraitImpls,
             ReprHints,
         }
@@ -230,6 +232,7 @@ impl<D: Clone + Debug> DepNode<D> {
             SizedConstraint(ref d) => op(d).map(SizedConstraint),
             AssociatedItemDefIds(ref d) => op(d).map(AssociatedItemDefIds),
             InherentImpls(ref d) => op(d).map(InherentImpls),
+            Tables(ref d) => op(d).map(Tables),
             TraitImpls(ref d) => op(d).map(TraitImpls),
             TraitItems(ref d) => op(d).map(TraitItems),
             ReprHints(ref d) => op(d).map(ReprHints),

src/librustc/hir/map/blocks.rs

@@ -45,15 +45,6 @@ pub struct FnLikeNode<'a> { node: map::Node<'a> }
 /// corresponds to some FnLikeNode.
 pub trait MaybeFnLike { fn is_fn_like(&self) -> bool; }
 
-/// Components shared by fn-like things (fn items, methods, closures).
-pub struct FnParts<'a> {
-    pub decl: &'a FnDecl,
-    pub body: ast::BodyId,
-    pub kind: FnKind<'a>,
-    pub span: Span,
-    pub id:   NodeId,
-}
-
 impl MaybeFnLike for ast::Item {
     fn is_fn_like(&self) -> bool {
         match self.node { ast::ItemFn(..) => true, _ => false, }
@@ -165,16 +156,6 @@ impl<'a> FnLikeNode<'a> {
         }
     }
 
-    pub fn to_fn_parts(self) -> FnParts<'a> {
-        FnParts {
-            decl: self.decl(),
-            body: self.body(),
-            kind: self.kind(),
-            span: self.span(),
-            id:   self.id(),
-        }
-    }
-
     pub fn body(self) -> ast::BodyId {
         self.handle(|i: ItemFnParts<'a>|  i.body,
                     |_, _, _: &'a ast::MethodSig, _, body: ast::BodyId, _, _|  body,

src/librustc/hir/map/collector.rs

@@ -23,10 +23,6 @@ pub struct NodeCollector<'ast> {
     pub(super) map: Vec<MapEntry<'ast>>,
     /// The parent of this node
     pub parent_node: NodeId,
-    /// If true, completely ignore nested items. We set this when loading
-    /// HIR from metadata, since in that case we only want the HIR for
-    /// one specific item (and not the ones nested inside of it).
-    pub ignore_nested_items: bool
 }
 
 impl<'ast> NodeCollector<'ast> {
@@ -35,30 +31,12 @@ impl<'ast> NodeCollector<'ast> {
             krate: krate,
             map: vec![],
             parent_node: CRATE_NODE_ID,
-            ignore_nested_items: false
         };
         collector.insert_entry(CRATE_NODE_ID, RootCrate);
 
         collector
     }
 
-    pub(super) fn extend(krate: &'ast Crate,
-                         parent: &'ast InlinedItem,
-                         parent_node: NodeId,
-                         map: Vec<MapEntry<'ast>>)
-                         -> NodeCollector<'ast> {
-        let mut collector = NodeCollector {
-            krate: krate,
-            map: map,
-            parent_node: parent_node,
-            ignore_nested_items: true
-        };
-
-        collector.insert_entry(parent_node, RootInlinedParent(parent));
-
-        collector
-    }
-
     fn insert_entry(&mut self, id: NodeId, entry: MapEntry<'ast>) {
         debug!("ast_map: {:?} => {:?}", id, entry);
         let len = self.map.len();
@@ -92,27 +70,19 @@ impl<'ast> Visitor<'ast> for NodeCollector<'ast> {
 
     fn visit_nested_item(&mut self, item: ItemId) {
         debug!("visit_nested_item: {:?}", item);
-        if !self.ignore_nested_items {
-            self.visit_item(self.krate.item(item.id))
-        }
+        self.visit_item(self.krate.item(item.id));
     }
 
     fn visit_nested_trait_item(&mut self, item_id: TraitItemId) {
-        if !self.ignore_nested_items {
-            self.visit_trait_item(self.krate.trait_item(item_id))
-        }
+        self.visit_trait_item(self.krate.trait_item(item_id));
     }
 
     fn visit_nested_impl_item(&mut self, item_id: ImplItemId) {
-        if !self.ignore_nested_items {
-            self.visit_impl_item(self.krate.impl_item(item_id))
-        }
+        self.visit_impl_item(self.krate.impl_item(item_id));
     }
 
     fn visit_nested_body(&mut self, id: BodyId) {
-        if !self.ignore_nested_items {
-            self.visit_body(self.krate.body(id))
-        }
+        self.visit_body(self.krate.body(id));
     }
 
     fn visit_item(&mut self, i: &'ast Item) {