Move next_node_id to Resolver

This doesn't migrate the pretty-printing everybody loops, which will be
done in the next few commits.

src/librustc_resolve/build_reduced_graph.rs

@@ -449,7 +449,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                                     name: kw::PathRoot,
                                     span: source.ident.span,
                                 },
-                                id: Some(self.r.session.next_node_id()),
+                                id: Some(self.r.next_node_id()),
                             });
                             source.ident.name = crate_name;
                         }

src/librustc_resolve/lib.rs

@@ -961,6 +961,8 @@ pub struct Resolver<'a> {
     variant_vis: DefIdMap<ty::Visibility>,
 
     lint_buffer: lint::LintBuffer,
+
+    next_node_id: NodeId,
 }
 
 /// Nothing really interesting here; it just provides memory for the rest of the crate.
@@ -1078,6 +1080,10 @@ impl<'a> hir::lowering::Resolver for Resolver<'a> {
     fn lint_buffer(&mut self) -> &mut lint::LintBuffer {
         &mut self.lint_buffer
     }
+
+    fn next_node_id(&mut self) -> NodeId {
+        self.next_node_id()
+    }
 }
 
 impl<'a> Resolver<'a> {
@@ -1226,9 +1232,26 @@ impl<'a> Resolver<'a> {
                     .collect(),
             variant_vis: Default::default(),
             lint_buffer: lint::LintBuffer::default(),
+            next_node_id: NodeId::from_u32(1),
         }
     }
 
+    pub fn reserve_node_ids(&mut self, count: usize) -> ast::NodeId {
+        let id = self.next_node_id;
+
+        match id.as_usize().checked_add(count) {
+            Some(next) => {
+                self.next_node_id = ast::NodeId::from_usize(next);
+            }
+            None => panic!("input too large; ran out of node-IDs!"),
+        }
+
+        id
+    }
+    pub fn next_node_id(&mut self) -> NodeId {
+        self.reserve_node_ids(1)
+    }
+
     pub fn lint_buffer(&mut self) -> &mut lint::LintBuffer {
         &mut self.lint_buffer
     }
@@ -2827,9 +2850,9 @@ impl<'a> Resolver<'a> {
         }
     }
 
-    fn new_ast_path_segment(&self, ident: Ident) -> ast::PathSegment {
+    fn new_ast_path_segment(&mut self, ident: Ident) -> ast::PathSegment {
         let mut seg = ast::PathSegment::from_ident(ident);
-        seg.id = self.session.next_node_id();
+        seg.id = self.next_node_id();
         seg
     }
 

src/librustc_resolve/macros.rs

@@ -95,7 +95,7 @@ fn fast_print_path(path: &ast::Path) -> Symbol {
 
 impl<'a> base::Resolver for Resolver<'a> {
     fn next_node_id(&mut self) -> NodeId {
-        self.session.next_node_id()
+        self.next_node_id()
     }
 
     fn resolve_dollar_crates(&mut self) {