try to cache region_scope_tree as a query

Author: dingxiangfei2009

clippy_lints/src/loops/needless_range_loop.rs

@@ -55,11 +55,7 @@ pub(super) fn check<'tcx>(
                 // ensure that the indexed variable was declared before the loop, see #601
                 if let Some(indexed_extent) = indexed_extent {
                     let parent_def_id = cx.tcx.hir().get_parent_item(expr.hir_id);
-                    let parent_body_id = cx
-                        .tcx
-                        .hir()
-                        .body_owned_by(cx.tcx.hir().local_def_id_to_hir_id(parent_def_id));
-                    let region_scope_tree = &cx.tcx.typeck_body(parent_body_id).region_scope_tree;
+                    let region_scope_tree = cx.tcx.region_scope_tree(parent_def_id);
                     let pat_extent = region_scope_tree.var_scope(pat.hir_id.local_id).unwrap();
                     if region_scope_tree.is_subscope_of(indexed_extent, pat_extent) {
                         return;
@@ -282,14 +278,9 @@ impl<'a, 'tcx> VarVisitor<'a, 'tcx> {
                 match res {
                     Res::Local(hir_id) => {
                         let parent_def_id = self.cx.tcx.hir().get_parent_item(expr.hir_id);
-                        let parent_body_id = self.cx
-                            .tcx
-                            .hir()
-                            .body_owned_by(self.cx.tcx.hir().local_def_id_to_hir_id(parent_def_id));
                         let extent = self.cx
                             .tcx
-                            .typeck_body(parent_body_id)
-                            .region_scope_tree
+                            .region_scope_tree(parent_def_id)
                             .var_scope(hir_id.local_id)
                             .unwrap();
                         if index_used_directly {

clippy_lints/src/shadow.rs

@@ -162,10 +162,7 @@ fn is_shadow(
     first: ItemLocalId,
     second: ItemLocalId,
 ) -> bool {
-    let scope_tree = &cx
-        .tcx
-        .typeck_body(cx.tcx.hir().body_owned_by(cx.tcx.hir().local_def_id_to_hir_id(owner)))
-        .region_scope_tree;
+    let scope_tree = cx.tcx.region_scope_tree(owner);
     let first_scope = scope_tree.var_scope(first).unwrap();
     let second_scope = scope_tree.var_scope(second).unwrap();
     scope_tree.is_subscope_of(second_scope, first_scope)