Auto merge of #81355 - jonas-schievink:rollup-vpaadij, r=jonas-schievink

Rollup of 14 pull requests

Successful merges:

 - #75180 (Implement Error for &(impl Error))
 - #78578 (Permit mutable references in all const contexts)
 - #79174 (Make std::future a re-export of core::future)
 - #79884 (Replace magic numbers with existing constants)
 - #80855 (Expand assert!(expr, args..) to include $crate for hygiene on 2021.)
 - #80933 (Fix sysroot option not being honored across rustc)
 - #81259 (Replace version_check dependency with own version parsing code)
 - #81264 (Add unstable option to control doctest run directory)
 - #81279 (Small refactor in typeck)
 - #81297 (Don't provide backend_optimization_level query for extern crates)
 - #81302 (Fix rendering of stabilization version for trait implementors)
 - #81310 (Do not mark unit variants as used when in path pattern)
 - #81320 (Make bad shlex parsing a pretty error)
 - #81338 (Clean up `dominators_given_rpo`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 5 insertions, 11 deletions

diff --git a/compiler/rustc_data_structures/src/graph/dominators/mod.rs b/compiler/rustc_data_structures/src/graph/dominators/mod.rs
index 1cfbce2355e..ad62e3c9fc8 100644
--- a/compiler/rustc_data_structures/src/graph/dominators/mod.rs
+++ b/compiler/rustc_data_structures/src/graph/dominators/mod.rs
@@ -8,7 +8,6 @@
 use super::iterate::reverse_post_order;
 use super::ControlFlowGraph;
 use rustc_index::vec::{Idx, IndexVec};
-use std::borrow::BorrowMut;
 use std::cmp::Ordering;
 
 #[cfg(test)]
@@ -20,22 +19,17 @@ pub fn dominators<G: ControlFlowGraph>(graph: G) -> Dominators<G::Node> {
     dominators_given_rpo(graph, &rpo)
 }
 
-fn dominators_given_rpo<G: ControlFlowGraph + BorrowMut<G>>(
-    mut graph: G,
-    rpo: &[G::Node],
-) -> Dominators<G::Node> {
-    let start_node = graph.borrow().start_node();
+fn dominators_given_rpo<G: ControlFlowGraph>(graph: G, rpo: &[G::Node]) -> Dominators<G::Node> {
+    let start_node = graph.start_node();
     assert_eq!(rpo[0], start_node);
 
     // compute the post order index (rank) for each node
-    let mut post_order_rank: IndexVec<G::Node, usize> =
-        (0..graph.borrow().num_nodes()).map(|_| 0).collect();
+    let mut post_order_rank = IndexVec::from_elem_n(0, graph.num_nodes());
     for (index, node) in rpo.iter().rev().cloned().enumerate() {
         post_order_rank[node] = index;
     }
 
-    let mut immediate_dominators: IndexVec<G::Node, Option<G::Node>> =
-        (0..graph.borrow().num_nodes()).map(|_| None).collect();
+    let mut immediate_dominators = IndexVec::from_elem_n(None, graph.num_nodes());
     immediate_dominators[start_node] = Some(start_node);
 
     let mut changed = true;
@@ -44,7 +38,7 @@ fn dominators_given_rpo<G: ControlFlowGraph + BorrowMut<G>>(
 
         for &node in &rpo[1..] {
             let mut new_idom = None;
-            for pred in graph.borrow_mut().predecessors(node) {
+            for pred in graph.predecessors(node) {
                 if immediate_dominators[pred].is_some() {
                     // (*) dominators for `pred` have been calculated
                     new_idom = Some(if let Some(new_idom) = new_idom {