From 06b2e659d3b7784b041a332920ae8630eaf954fd Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Thu, 21 Oct 2021 19:22:44 +0200
Subject: [PATCH] Remove unused root_parent.

---
 compiler/rustc_middle/src/middle/region.rs | 16 ++++------------
 compiler/rustc_passes/src/region.rs        | 14 +-------------
 2 files changed, 5 insertions(+), 25 deletions(-)

diff --git a/compiler/rustc_middle/src/middle/region.rs b/compiler/rustc_middle/src/middle/region.rs
index 605e0bc2e63..39ca41c92ff 100644
--- a/compiler/rustc_middle/src/middle/region.rs
+++ b/compiler/rustc_middle/src/middle/region.rs
@@ -7,13 +7,12 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/borrow_check.html
 
 use crate::ty::TyCtxt;
-use rustc_hir as hir;
-use rustc_hir::Node;
-use rustc_query_system::ich::{NodeIdHashingMode, StableHashingContext};
-
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_hir as hir;
+use rustc_hir::Node;
 use rustc_macros::HashStable;
+use rustc_query_system::ich::{NodeIdHashingMode, StableHashingContext};
 use rustc_span::{Span, DUMMY_SP};
 
 use std::fmt;
@@ -210,11 +209,6 @@ pub struct ScopeTree {
     /// If not empty, this body is the root of this region hierarchy.
     pub root_body: Option<hir::HirId>,
 
-    /// The parent of the root body owner, if the latter is an
-    /// an associated const or method, as impls/traits can also
-    /// have lifetime parameters free in this body.
-    pub root_parent: Option<hir::HirId>,
-
     /// Maps from a scope ID to the enclosing scope id;
     /// this is usually corresponding to the lexical nesting, though
     /// in the case of closures the parent scope is the innermost
@@ -445,7 +439,6 @@ impl<'a> HashStable<StableHashingContext<'a>> for ScopeTree {
     fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
         let ScopeTree {
             root_body,
-            root_parent,
             ref body_expr_count,
             ref parent_map,
             ref var_map,
@@ -455,8 +448,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for ScopeTree {
         } = *self;
 
         hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
-            root_body.hash_stable(hcx, hasher);
-            root_parent.hash_stable(hcx, hasher);
+            root_body.hash_stable(hcx, hasher)
         });
 
         body_expr_count.hash_stable(hcx, hasher);
diff --git a/compiler/rustc_passes/src/region.rs b/compiler/rustc_passes/src/region.rs
index 6a8feb041da..ae423070392 100644
--- a/compiler/rustc_passes/src/region.rs
+++ b/compiler/rustc_passes/src/region.rs
@@ -11,7 +11,7 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
-use rustc_hir::{Arm, Block, Expr, Local, Node, Pat, PatKind, Stmt};
+use rustc_hir::{Arm, Block, Expr, Local, Pat, PatKind, Stmt};
 use rustc_index::vec::Idx;
 use rustc_middle::middle::region::*;
 use rustc_middle::ty::query::Providers;
@@ -837,19 +837,7 @@ fn region_scope_tree(tcx: TyCtxt<'_>, def_id: DefId) -> &ScopeTree {
 
         let body = tcx.hir().body(body_id);
         visitor.scope_tree.root_body = Some(body.value.hir_id);
-
-        // If the item is an associated const or a method,
-        // record its impl/trait parent, as it can also have
-        // lifetime parameters free in this body.
-        match tcx.hir().get(id) {
-            Node::ImplItem(_) | Node::TraitItem(_) => {
-                visitor.scope_tree.root_parent = Some(tcx.hir().get_parent_item(id));
-            }
-            _ => {}
-        }
-
         visitor.visit_body(body);
-
         visitor.scope_tree
     } else {
         ScopeTree::default()