From a5258d17216d122bfc27f4aad316689f8d29a62a Mon Sep 17 00:00:00 2001
From: lcnr <rust@lcnr.de>
Date: Thu, 9 Mar 2023 12:53:03 +0100
Subject: [PATCH] no more do while

---
 .../rustc_mir_build/src/build/matches/mod.rs  |  8 ++--
 .../rustc_mir_transform/src/coverage/graph.rs | 40 +++++++++----------
 2 files changed, 23 insertions(+), 25 deletions(-)

diff --git a/compiler/rustc_mir_build/src/build/matches/mod.rs b/compiler/rustc_mir_build/src/build/matches/mod.rs
index de2851a1af9fd..2984dfa735e0a 100644
--- a/compiler/rustc_mir_build/src/build/matches/mod.rs
+++ b/compiler/rustc_mir_build/src/build/matches/mod.rs
@@ -581,8 +581,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         // let PATTERN = ... might not even exist until we do the assignment.
         // so we set it here instead.
         if set_match_place {
-            let mut candidate_ref = &candidate;
-            while let Some(next) = {
+            let mut next = Some(&candidate);
+            while let Some(candidate_ref) = next.take() {
                 for binding in &candidate_ref.bindings {
                     let local = self.var_local_id(binding.var_id, OutsideGuard);
                     // `try_to_place` may fail if it is unable to resolve the given
@@ -610,9 +610,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 }
                 // All of the subcandidates should bind the same locals, so we
                 // only visit the first one.
-                candidate_ref.subcandidates.get(0)
-            } {
-                candidate_ref = next;
+                next = candidate_ref.subcandidates.get(0)
             }
         }
 
diff --git a/compiler/rustc_mir_transform/src/coverage/graph.rs b/compiler/rustc_mir_transform/src/coverage/graph.rs
index a2671eef2e940..87cac7702dc50 100644
--- a/compiler/rustc_mir_transform/src/coverage/graph.rs
+++ b/compiler/rustc_mir_transform/src/coverage/graph.rs
@@ -538,29 +538,29 @@ impl TraverseCoverageGraphWithLoops {
             "TraverseCoverageGraphWithLoops::next - context_stack: {:?}",
             self.context_stack.iter().rev().collect::<Vec<_>>()
         );
-        while let Some(next_bcb) = {
-            // Strip contexts with empty worklists from the top of the stack
-            while self.context_stack.last().map_or(false, |context| context.worklist.is_empty()) {
+
+        while let Some(context) = self.context_stack.last_mut() {
+            if let Some(next_bcb) = context.worklist.pop() {
+                if !self.visited.insert(next_bcb) {
+                    debug!("Already visited: {:?}", next_bcb);
+                    continue;
+                }
+                debug!("Visiting {:?}", next_bcb);
+                if self.backedges[next_bcb].len() > 0 {
+                    debug!("{:?} is a loop header! Start a new TraversalContext...", next_bcb);
+                    self.context_stack.push(TraversalContext {
+                        loop_backedges: Some((self.backedges[next_bcb].clone(), next_bcb)),
+                        worklist: Vec::new(),
+                    });
+                }
+                self.extend_worklist(basic_coverage_blocks, next_bcb);
+                return Some(next_bcb);
+            } else {
+                // Strip contexts with empty worklists from the top of the stack
                 self.context_stack.pop();
             }
-            // Pop the next bcb off of the current context_stack. If none, all BCBs were visited.
-            self.context_stack.last_mut().map_or(None, |context| context.worklist.pop())
-        } {
-            if !self.visited.insert(next_bcb) {
-                debug!("Already visited: {:?}", next_bcb);
-                continue;
-            }
-            debug!("Visiting {:?}", next_bcb);
-            if self.backedges[next_bcb].len() > 0 {
-                debug!("{:?} is a loop header! Start a new TraversalContext...", next_bcb);
-                self.context_stack.push(TraversalContext {
-                    loop_backedges: Some((self.backedges[next_bcb].clone(), next_bcb)),
-                    worklist: Vec::new(),
-                });
-            }
-            self.extend_worklist(basic_coverage_blocks, next_bcb);
-            return Some(next_bcb);
         }
+
         None
     }