Split nested_visit_mode function off from nested_visit_map

... and make the latter mandatory to implement.

src/librustc/hir/intravisit.rs

@@ -95,14 +95,13 @@ pub trait Visitor<'v> : Sized {
     ///////////////////////////////////////////////////////////////////////////
     // Nested items.
 
-    /// The default versions of the `visit_nested_XXX` routines invoke
-    /// this method to get a map to use; if they get back `None`, they
-    /// just skip nested things. Otherwise, they will lookup the
-    /// nested item-like things in the map and visit it. So the best
-    /// way to implement a nested visitor is to override this method
-    /// to return a `Map`; one advantage of this is that if we add
-    /// more types of nested things in the future, they will
-    /// automatically work.
+    /// The default versions of the `visit_nested_XXX` routines invoke this
+    /// method to get a map to use; if they get back `None`, they just skip
+    /// nested things. Otherwise, they will lookup the nested thing in the map
+    /// and visit it depending on what `nested_visit_mode` returns. So the best
+    /// way to implement a nested visitor is to override this method to return a
+    /// `Map`; one advantage of this is that if we add more types of nested
+    /// things in the future, they will automatically work.
     ///
     /// **If for some reason you want the nested behavior, but don't
     /// have a `Map` are your disposal:** then you should override the
@@ -110,8 +109,12 @@ pub trait Visitor<'v> : Sized {
     /// `panic!()`. This way, if a new `visit_nested_XXX` variant is
     /// added in the future, we will see the panic in your code and
     /// fix it appropriately.
-    fn nested_visit_map(&mut self) -> Option<(&Map<'v>, NestedVisitMode)> {
-        None
+    fn nested_visit_map(&mut self) -> Option<&Map<'v>>;
+
+    /// Specifies what things nested things this visitor wants to visit. By
+    /// default, bodies will be visited, but not nested items.
+    fn nested_visit_mode(&mut self) -> NestedVisitMode {
+        NestedVisitMode::OnlyBodies
     }
 
     /// Invoked when a nested item is encountered. By default does
@@ -300,16 +303,15 @@ pub trait Visitor<'v> : Sized {
 }
 
 fn map_for_body<'v, V: Visitor<'v>>(visitor: &mut V) -> Option<&Map<'v>> {
-    visitor.nested_visit_map().map(|(map, _mode)| map)
+    visitor.nested_visit_map()
 }
 
 fn map_for_item<'v, V: Visitor<'v>>(visitor: &mut V) -> Option<&Map<'v>> {
-    visitor.nested_visit_map().and_then(|(map, mode)| {
-        match mode {
-            NestedVisitMode::OnlyBodies => None,
-            NestedVisitMode::All => Some(map)
-        }
-    })
+    match visitor.nested_visit_mode() {
+        NestedVisitMode::OnlyBodies => None,
+        NestedVisitMode::All => Some(visitor.nested_visit_map()
+                                     .expect("NestedVisitMode::All without nested_visit_map"))
+    }
 }
 
 pub fn walk_opt_name<'v, V: Visitor<'v>>(visitor: &mut V, span: Span, opt_name: Option<Name>) {
@@ -1059,8 +1061,8 @@ impl<'a, 'ast> IdRangeComputingVisitor<'a, 'ast> {
 }
 
 impl<'a, 'ast> Visitor<'ast> for IdRangeComputingVisitor<'a, 'ast> {
-    fn nested_visit_map(&mut self) -> Option<(&Map<'ast>, NestedVisitMode)> {
-        Some((&self.map, NestedVisitMode::OnlyBodies))
+    fn nested_visit_map(&mut self) -> Option<&Map<'ast>> {
+        Some(&self.map)
     }
 
     fn visit_id(&mut self, id: NodeId) {

src/librustc/hir/map/collector.rs

@@ -10,7 +10,7 @@
 
 use super::*;
 
-use hir::intravisit::{Visitor, NestedVisitMode};
+use hir::intravisit::Visitor;
 use hir::def_id::DefId;
 use middle::cstore::InlinedItem;
 use std::iter::repeat;
@@ -91,7 +91,7 @@ impl<'ast> Visitor<'ast> for NodeCollector<'ast> {
     /// deep walking so that we walk nested items in the context of
     /// their outer items.
 
-    fn nested_visit_map(&mut self) -> Option<(&map::Map<'ast>, NestedVisitMode)> {
+    fn nested_visit_map(&mut self) -> Option<&map::Map<'ast>> {
         panic!("visit_nested_xxx must be manually implemented in this visitor")
     }
 

src/librustc/hir/map/def_collector.rs

@@ -327,6 +327,10 @@ impl<'a> visit::Visitor for DefCollector<'a> {
 
 // We walk the HIR rather than the AST when reading items from metadata.
 impl<'ast> intravisit::Visitor<'ast> for DefCollector<'ast> {
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'ast>> {
+        None
+    }
+
     fn visit_body(&mut self, id: hir::ExprId) {
         if let Some(krate) = self.hir_crate {
             self.visit_expr(krate.expr(id));

src/librustc/lint/context.rs

@@ -791,8 +791,12 @@ impl<'a, 'tcx> hir_visit::Visitor<'tcx> for LateContext<'a, 'tcx> {
     /// Because lints are scoped lexically, we want to walk nested
     /// items in the context of the outer item, so enable
     /// deep-walking.
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, hir_visit::NestedVisitMode)> {
-        Some((&self.tcx.map, hir_visit::NestedVisitMode::All))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.tcx.map)
+    }
+
+    fn nested_visit_mode(&mut self) -> hir_visit::NestedVisitMode {
+        hir_visit::NestedVisitMode::All
     }
 
     fn visit_item(&mut self, it: &'tcx hir::Item) {
@@ -1109,8 +1113,8 @@ struct IdVisitor<'a, 'b: 'a, 'tcx: 'a+'b> {
 
 // Output any lints that were previously added to the session.
 impl<'a, 'b, 'tcx> hir_visit::Visitor<'tcx> for IdVisitor<'a, 'b, 'tcx> {
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, hir_visit::NestedVisitMode)> {
-        Some((&self.cx.tcx.map, hir_visit::NestedVisitMode::OnlyBodies))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.cx.tcx.map)
     }
 
     fn visit_id(&mut self, id: ast::NodeId) {

src/librustc/middle/dataflow.rs

@@ -193,6 +193,8 @@ fn build_nodeid_to_index(decl: Option<&hir::FnDecl>,
         let mut formals = Formals { entry: entry, index: index };
         intravisit::walk_fn_decl(&mut formals, decl);
         impl<'a, 'v> intravisit::Visitor<'v> for Formals<'a> {
+            fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'v>> { None }
+
             fn visit_pat(&mut self, p: &hir::Pat) {
                 self.index.entry(p.id).or_insert(vec![]).push(self.entry);
                 intravisit::walk_pat(self, p)

src/librustc/middle/dead.rs

@@ -221,8 +221,8 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for MarkSymbolVisitor<'a, 'tcx> {
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, NestedVisitMode)> {
-        Some((&self.tcx.map, NestedVisitMode::OnlyBodies))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.tcx.map)
     }
 
     fn visit_variant_data(&mut self, def: &'tcx hir::VariantData, _: ast::Name,
@@ -510,10 +510,12 @@ impl<'a, 'tcx> Visitor<'tcx> for DeadVisitor<'a, 'tcx> {
     /// on inner functions when the outer function is already getting
     /// an error. We could do this also by checking the parents, but
     /// this is how the code is setup and it seems harmless enough.
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, NestedVisitMode)> {
-        Some((&self.tcx.map, NestedVisitMode::All))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.tcx.map)
     }
 
+    fn nested_visit_mode(&mut self) -> NestedVisitMode { NestedVisitMode::All }
+
     fn visit_item(&mut self, item: &'tcx hir::Item) {
         if self.should_warn_about_item(item) {
             self.warn_dead_code(

src/librustc/middle/effect.rs

@@ -21,7 +21,7 @@ use syntax::ast;
 use syntax_pos::Span;
 use hir::{self, PatKind};
 use hir::def::Def;
-use hir::intravisit::{self, FnKind, Visitor, NestedVisitMode};
+use hir::intravisit::{self, FnKind, Visitor};
 
 #[derive(Copy, Clone)]
 struct UnsafeContext {
@@ -93,8 +93,8 @@ impl<'a, 'tcx> EffectCheckVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for EffectCheckVisitor<'a, 'tcx> {
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, NestedVisitMode)> {
-        Some((&self.tcx.map, NestedVisitMode::OnlyBodies))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.tcx.map)
     }
 
     fn visit_fn(&mut self, fn_kind: FnKind<'tcx>, fn_decl: &'tcx hir::FnDecl,

src/librustc/middle/intrinsicck.rs

@@ -19,7 +19,7 @@ use ty::layout::{LayoutError, Pointer, SizeSkeleton};
 use syntax::abi::Abi::RustIntrinsic;
 use syntax::ast;
 use syntax_pos::Span;
-use hir::intravisit::{self, Visitor, FnKind, NestedVisitMode};
+use hir::intravisit::{self, Visitor, FnKind};
 use hir;
 
 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
@@ -117,8 +117,8 @@ impl<'a, 'gcx, 'tcx> ExprVisitor<'a, 'gcx, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for ItemVisitor<'a, 'tcx> {
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, NestedVisitMode)> {
-        Some((&self.tcx.map, NestedVisitMode::OnlyBodies))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.tcx.map)
     }
 
     // const, static and N in [T; N].
@@ -163,8 +163,8 @@ impl<'a, 'tcx> Visitor<'tcx> for ItemVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for ExprVisitor<'a, 'gcx, 'tcx> {
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'gcx>, NestedVisitMode)> {
-        Some((&self.infcx.tcx.map, NestedVisitMode::OnlyBodies))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'gcx>> {
+        Some(&self.infcx.tcx.map)
     }
 
     fn visit_expr(&mut self, expr: &'gcx hir::Expr) {

src/librustc/middle/liveness.rs

@@ -128,7 +128,7 @@ use syntax_pos::Span;
 use hir::Expr;
 use hir;
 use hir::print::{expr_to_string, block_to_string};
-use hir::intravisit::{self, Visitor, FnKind, NestedVisitMode};
+use hir::intravisit::{self, Visitor, FnKind};
 
 /// For use with `propagate_through_loop`.
 enum LoopKind<'a> {
@@ -183,8 +183,8 @@ fn live_node_kind_to_string(lnk: LiveNodeKind, tcx: TyCtxt) -> String {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for IrMaps<'a, 'tcx> {
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, NestedVisitMode)> {
-        Some((&self.tcx.map, NestedVisitMode::OnlyBodies))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.tcx.map)
     }
     fn visit_fn(&mut self, fk: FnKind<'tcx>, fd: &'tcx hir::FnDecl,
                 b: hir::ExprId, s: Span, id: NodeId) {
@@ -352,8 +352,8 @@ impl<'a, 'tcx> IrMaps<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for Liveness<'a, 'tcx> {
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, NestedVisitMode)> {
-        Some((&self.ir.tcx.map, NestedVisitMode::OnlyBodies))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.ir.tcx.map)
     }
     fn visit_fn(&mut self, _: FnKind<'tcx>, _: &'tcx hir::FnDecl,
                 _: hir::ExprId, _: Span, _: NodeId) {

src/librustc/middle/reachable.rs

@@ -28,7 +28,7 @@ use syntax::abi::Abi;
 use syntax::ast;
 use syntax::attr;
 use hir;
-use hir::intravisit::{Visitor, NestedVisitMode};
+use hir::intravisit::{Visitor};
 use hir::itemlikevisit::ItemLikeVisitor;
 use hir::intravisit;
 
@@ -89,8 +89,8 @@ struct ReachableContext<'a, 'tcx: 'a> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for ReachableContext<'a, 'tcx> {
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, NestedVisitMode)> {
-        Some((&self.tcx.map, NestedVisitMode::OnlyBodies))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.tcx.map)
     }
 
     fn visit_expr(&mut self, expr: &'tcx hir::Expr) {

src/librustc/middle/region.rs

@@ -31,7 +31,7 @@ use syntax::ast::{self, NodeId};
 use syntax_pos::Span;
 
 use hir;
-use hir::intravisit::{self, Visitor, FnKind, NestedVisitMode};
+use hir::intravisit::{self, Visitor, FnKind};
 use hir::{Block, Item, FnDecl, Arm, Pat, PatKind, Stmt, Expr, Local};
 
 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, RustcEncodable,
@@ -1170,8 +1170,8 @@ impl<'ast, 'a> RegionResolutionVisitor<'ast, 'a> {
 }
 
 impl<'ast, 'a> Visitor<'ast> for RegionResolutionVisitor<'ast, 'a> {
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'ast>, NestedVisitMode)> {
-        Some((&self.map, NestedVisitMode::OnlyBodies))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'ast>> {
+        Some(&self.map)
     }
 
     fn visit_block(&mut self, b: &'ast Block) {

src/librustc/middle/resolve_lifetime.rs

@@ -132,10 +132,12 @@ pub fn krate(sess: &Session,
 impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
     // Override the nested functions -- lifetimes follow lexical scope,
     // so it's convenient to walk the tree in lexical order.
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, NestedVisitMode)> {
-        Some((&self.hir_map, NestedVisitMode::All))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.hir_map)
     }
 
+    fn nested_visit_mode(&mut self) -> NestedVisitMode { NestedVisitMode::All }
+
     fn visit_item(&mut self, item: &'tcx hir::Item) {
         // Save labels for nested items.
         let saved_labels_in_fn = replace(&mut self.labels_in_fn, vec![]);
@@ -423,6 +425,8 @@ fn extract_labels(ctxt: &mut LifetimeContext, b: hir::ExprId) {
     return;
 
     impl<'v, 'a> Visitor<'v> for GatherLabels<'a> {
+        fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'v>> { None }
+
         fn visit_expr(&mut self, ex: &'v hir::Expr) {
             // do not recurse into closures defined in the block
             // since they are treated as separate fns from the POV of
@@ -938,6 +942,8 @@ fn insert_late_bound_lifetimes(map: &mut NamedRegionMap,
     }
 
     impl<'v> Visitor<'v> for ConstrainedCollector {
+        fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'v>> { None }
+
         fn visit_ty(&mut self, ty: &'v hir::Ty) {
             match ty.node {
                 hir::TyPath(hir::QPath::Resolved(Some(_), _)) |
@@ -975,6 +981,8 @@ fn insert_late_bound_lifetimes(map: &mut NamedRegionMap,
     }
 
     impl<'v> Visitor<'v> for AllCollector {
+        fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'v>> { None }
+
         fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) {
             self.regions.insert(lifetime_ref.name);
         }

src/librustc/middle/stability.rs

@@ -234,10 +234,12 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
     /// Because stability levels are scoped lexically, we want to walk
     /// nested items in the context of the outer item, so enable
     /// deep-walking.
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, NestedVisitMode)> {
-        Some((&self.tcx.map, NestedVisitMode::All))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.tcx.map)
     }
 
+    fn nested_visit_mode(&mut self) -> NestedVisitMode { NestedVisitMode::All }
+
     fn visit_item(&mut self, i: &'tcx Item) {
         let orig_in_trait_impl = self.in_trait_impl;
         let mut kind = AnnotationKind::Required;
@@ -534,10 +536,12 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
-    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, NestedVisitMode)> {
-        Some((&self.tcx.map, NestedVisitMode::OnlyBodies))
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'tcx>> {
+        Some(&self.tcx.map)
     }
 
+    fn nested_visit_mode(&mut self) -> NestedVisitMode { NestedVisitMode::OnlyBodies }
+
     fn visit_item(&mut self, item: &'tcx hir::Item) {
         match item.node {
             hir::ItemExternCrate(_) => {

src/librustc/middle/weak_lang_items.rs

@@ -125,6 +125,8 @@ impl<'a> Context<'a> {
 }
 
 impl<'a, 'v> Visitor<'v> for Context<'a> {
+    fn nested_visit_map(&mut self) -> Option<&hir::map::Map<'v>> { None }
+
     fn visit_foreign_item(&mut self, i: &hir::ForeignItem) {
         if let Some(lang_item) = lang_items::extract(&i.attrs) {
             self.register(&lang_item.as_str(), i.span);