Remove unused Map::hir_node_by_def_id method.

Author: nnethercote

Diff for: compiler/rustc_hir/src/intravisit.rs

@@ -110,7 +110,6 @@ impl<'a> FnKind<'a> {
 pub trait Map<'hir> {
     /// Retrieves the `Node` corresponding to `id`.
     fn hir_node(&self, hir_id: HirId) -> Node<'hir>;
-    fn hir_node_by_def_id(&self, def_id: LocalDefId) -> Node<'hir>;
     fn body(&self, id: BodyId) -> &'hir Body<'hir>;
     fn item(&self, id: ItemId) -> &'hir Item<'hir>;
     fn trait_item(&self, id: TraitItemId) -> &'hir TraitItem<'hir>;
@@ -123,9 +122,6 @@ impl<'hir> Map<'hir> for ! {
     fn hir_node(&self, _: HirId) -> Node<'hir> {
         unreachable!();
     }
-    fn hir_node_by_def_id(&self, _: LocalDefId) -> Node<'hir> {
-        *self;
-    }
     fn body(&self, _: BodyId) -> &'hir Body<'hir> {
         unreachable!();
     }

Diff for: compiler/rustc_middle/src/hir/map.rs

@@ -1019,10 +1019,6 @@ impl<'hir> intravisit::Map<'hir> for Map<'hir> {
         self.tcx.hir_node(hir_id)
     }
 
-    fn hir_node_by_def_id(&self, def_id: LocalDefId) -> Node<'hir> {
-        self.tcx.hir_node_by_def_id(def_id)
-    }
-
     fn body(&self, id: BodyId) -> &'hir Body<'hir> {
         (*self).body(id)
     }