Make all hir::Map methods consistently by-value

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -763,7 +763,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             HirId, ImplItem, ImplItemKind, Item, ItemKind,
         };
 
-        fn maybe_body_id_of_fn(hir_map: &Map<'_>, id: HirId) -> Option<BodyId> {
+        fn maybe_body_id_of_fn(hir_map: Map<'_>, id: HirId) -> Option<BodyId> {
             match hir_map.find(id) {
                 Some(Node::Item(Item { kind: ItemKind::Fn(_, _, body_id), .. }))
                 | Some(Node::ImplItem(ImplItem { kind: ImplItemKind::Fn(_, body_id), .. })) => {
@@ -774,7 +774,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         }
         let hir_map = self.infcx.tcx.hir();
         let mir_body_hir_id = self.mir_hir_id();
-        if let Some(fn_body_id) = maybe_body_id_of_fn(&hir_map, mir_body_hir_id) {
+        if let Some(fn_body_id) = maybe_body_id_of_fn(hir_map, mir_body_hir_id) {
             if let Block(
                 hir::Block {
                     expr:

compiler/rustc_hir/src/intravisit.rs

@@ -141,22 +141,22 @@ pub trait Map<'hir> {
 // Used when no map is actually available, forcing manual implementation of nested visitors.
 impl<'hir> Map<'hir> for ! {
     fn find(&self, _: HirId) -> Option<Node<'hir>> {
-        unreachable!()
+        *self;
     }
     fn body(&self, _: BodyId) -> &'hir Body<'hir> {
-        unreachable!()
+        *self;
     }
     fn item(&self, _: ItemId) -> &'hir Item<'hir> {
-        unreachable!()
+        *self;
     }
     fn trait_item(&self, _: TraitItemId) -> &'hir TraitItem<'hir> {
-        unreachable!()
+        *self;
     }
     fn impl_item(&self, _: ImplItemId) -> &'hir ImplItem<'hir> {
-        unreachable!()
+        *self;
     }
     fn foreign_item(&self, _: ForeignItemId) -> &'hir ForeignItem<'hir> {
-        unreachable!()
+        *self;
     }
 }
 

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -2226,7 +2226,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         bound_kind: GenericKind<'tcx>,
         sub: Region<'tcx>,
     ) -> DiagnosticBuilder<'a> {
-        let hir = &self.tcx.hir();
+        let hir = self.tcx.hir();
         // Attempt to obtain the span of the parameter so we can
         // suggest adding an explicit lifetime bound to it.
         let generics = self