scrap find_node_for_hir_id in favor of hir_to_node_id

Michael Woerister pointed out that `hir_to_node_id` (introduced in
August 2017's 28ddd7a4e) supersedes the functionality of
`find_node_for_hir_id` (just a hash lookup compared to that linear
search).

src/librustc/hir/map/definitions.rs

@@ -487,14 +487,6 @@ impl Definitions {
         self.node_to_hir_id[node_id]
     }
 
-    pub fn find_node_for_hir_id(&self, hir_id: hir::HirId) -> ast::NodeId {
-        self.node_to_hir_id
-            .iter()
-            .position(|x| *x == hir_id)
-            .map(|idx| ast::NodeId::new(idx))
-            .unwrap()
-    }
-
     #[inline]
     pub fn def_index_to_hir_id(&self, def_index: DefIndex) -> hir::HirId {
         let space_index = def_index.address_space().index();

src/librustc/middle/expr_use_visitor.rs

@@ -609,8 +609,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
         match local.init {
             None => {
                 local.pat.each_binding(|_, hir_id, span, _| {
-                    // FIXME: converting HirId → NodeId is said to be relatively expensive
-                    let node_id = self.mc.tcx.hir.definitions().find_node_for_hir_id(hir_id);
+                    let node_id = self.mc.tcx.hir.hir_to_node_id(hir_id);
                     self.delegate.decl_without_init(node_id, span);
                 })
             }

src/librustc/middle/mem_categorization.rs

@@ -488,7 +488,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
             // FIXME
             None if self.is_tainted_by_errors() => Err(()),
             None => {
-                let id = self.tcx.hir.definitions().find_node_for_hir_id(id);
+                let id = self.tcx.hir.hir_to_node_id(id);
                 bug!("no type for node {}: {} in mem_categorization",
                      id, self.tcx.hir.node_to_string(id));
             }

src/librustc/ty/context.rs

@@ -266,9 +266,7 @@ fn validate_hir_id_for_typeck_tables(local_id_root: Option<DefId>,
         if let Some(local_id_root) = local_id_root {
             if hir_id.owner != local_id_root.index {
                 ty::tls::with(|tcx| {
-                    let node_id = tcx.hir
-                                     .definitions()
-                                     .find_node_for_hir_id(hir_id);
+                    let node_id = tcx.hir.hir_to_node_id(hir_id);
 
                     bug!("node {} with HirId::owner {:?} cannot be placed in \
                           TypeckTables with local_id_root {:?}",
@@ -527,7 +525,7 @@ impl<'tcx> TypeckTables<'tcx> {
             None => {
                 bug!("node_id_to_type: no type for node `{}`",
                     tls::with(|tcx| {
-                        let id = tcx.hir.definitions().find_node_for_hir_id(id);
+                        let id = tcx.hir.hir_to_node_id(id);
                         tcx.hir.node_to_string(id)
                     }))
             }
@@ -2616,8 +2614,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                                                     msg: &str)
         -> DiagnosticBuilder<'tcx>
     {
-        // FIXME: converting HirId → NodeId is said to be relatively expensive
-        let node_id = self.hir.definitions().find_node_for_hir_id(hir_id);
+        let node_id = self.hir.hir_to_node_id(hir_id);
         let (level, src) = self.lint_level_at_node(lint, node_id);
         lint::struct_lint_level(self.sess, lint, level, src, Some(span.into()), msg)
     }

src/librustc_typeck/check/mod.rs

@@ -2110,7 +2110,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             Some(&t) => t,
             None if self.is_tainted_by_errors() => self.tcx.types.err,
             None => {
-                let node_id = self.tcx.hir.definitions().find_node_for_hir_id(id);
+                let node_id = self.tcx.hir.hir_to_node_id(id);
                 bug!("no type for node {}: {} in fcx {}",
                      node_id, self.tcx.hir.node_to_string(node_id),
                      self.tag());

src/librustc_typeck/check/writeback.rs

@@ -560,7 +560,7 @@ impl Locatable for DefIndex {
 
 impl Locatable for hir::HirId {
     fn to_span(&self, tcx: &TyCtxt) -> Span {
-        let node_id = tcx.hir.definitions().find_node_for_hir_id(*self);
+        let node_id = tcx.hir.hir_to_node_id(*self);
         tcx.hir.span(node_id)
     }
 }

src/librustc_typeck/check_unused.rs

@@ -106,7 +106,7 @@ pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
         }
         assert_eq!(def_id.krate, LOCAL_CRATE);
         let hir_id = tcx.hir.definitions().def_index_to_hir_id(def_id.index);
-        let id = tcx.hir.definitions().find_node_for_hir_id(hir_id);
+        let id = tcx.hir.hir_to_node_id(hir_id);
         let lint = lint::builtin::UNUSED_EXTERN_CRATES;
         let msg = "unused extern crate";
         tcx.lint_node(lint, id, span, msg);