From d167408cb4efff3c0a5e404dbe5f097b87fa54fa Mon Sep 17 00:00:00 2001
From: ljedrz <ljedrz@gmail.com>
Date: Thu, 16 Apr 2020 14:24:52 +0200
Subject: [PATCH 1/3] simplify unused unsafe block handling

---
 src/librustc_mir/transform/check_unsafety.rs | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/src/librustc_mir/transform/check_unsafety.rs b/src/librustc_mir/transform/check_unsafety.rs
index 3ce9b875e16cc..595b0432015b3 100644
--- a/src/librustc_mir/transform/check_unsafety.rs
+++ b/src/librustc_mir/transform/check_unsafety.rs
@@ -641,13 +641,17 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: DefId) {
         }
     }
 
-    let mut unsafe_blocks: Vec<_> = unsafe_blocks.iter().collect();
-    unsafe_blocks.sort_by_cached_key(|(hir_id, _)| tcx.hir().hir_id_to_node_id(*hir_id));
-    let used_unsafe: FxHashSet<_> =
-        unsafe_blocks.iter().flat_map(|&&(id, used)| used.then_some(id)).collect();
-    for &(block_id, is_used) in unsafe_blocks {
-        if !is_used {
-            report_unused_unsafe(tcx, &used_unsafe, block_id);
+    let (mut unsafe_used, mut unsafe_unused): (FxHashSet<_>, Vec<_>) = Default::default();
+    for &(block_id, is_used) in unsafe_blocks.iter() {
+        if is_used {
+            unsafe_used.insert(block_id);
+        } else {
+            unsafe_unused.push(block_id);
         }
     }
+    unsafe_unused.sort_by_cached_key(|hir_id| tcx.hir().hir_id_to_node_id(*hir_id));
+
+    for &block_id in &unsafe_unused {
+        report_unused_unsafe(tcx, &unsafe_used, block_id);
+    }
 }

From 672b7682b0e836d87ad4e06e0fed2daaa6c065e6 Mon Sep 17 00:00:00 2001
From: ljedrz <ljedrz@gmail.com>
Date: Thu, 16 Apr 2020 14:53:09 +0200
Subject: [PATCH 2/3] sort unused unsafe blocks by Span instead of NodeId

---
 src/librustc_mir/transform/check_unsafety.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/librustc_mir/transform/check_unsafety.rs b/src/librustc_mir/transform/check_unsafety.rs
index 595b0432015b3..567fa42c83ae1 100644
--- a/src/librustc_mir/transform/check_unsafety.rs
+++ b/src/librustc_mir/transform/check_unsafety.rs
@@ -649,7 +649,7 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: DefId) {
             unsafe_unused.push(block_id);
         }
     }
-    unsafe_unused.sort_by_cached_key(|hir_id| tcx.hir().hir_id_to_node_id(*hir_id));
+    unsafe_unused.sort_by_cached_key(|hir_id| tcx.hir().span(*hir_id));
 
     for &block_id in &unsafe_unused {
         report_unused_unsafe(tcx, &unsafe_used, block_id);

From 66575c9962188aa2f16df04fa1fef1786f0d216f Mon Sep 17 00:00:00 2001
From: ljedrz <ljedrz@gmail.com>
Date: Thu, 16 Apr 2020 20:00:54 +0200
Subject: [PATCH 3/3] comment on the sorting of unused unsafe blocks

---
 src/librustc_mir/transform/check_unsafety.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/librustc_mir/transform/check_unsafety.rs b/src/librustc_mir/transform/check_unsafety.rs
index 567fa42c83ae1..9f6b1963ce794 100644
--- a/src/librustc_mir/transform/check_unsafety.rs
+++ b/src/librustc_mir/transform/check_unsafety.rs
@@ -649,6 +649,8 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: DefId) {
             unsafe_unused.push(block_id);
         }
     }
+    // The unused unsafe blocks might not be in source order; sort them so that the unused unsafe
+    // error messages are properly aligned and the issue-45107 and lint-unused-unsafe tests pass.
     unsafe_unused.sort_by_cached_key(|hir_id| tcx.hir().span(*hir_id));
 
     for &block_id in &unsafe_unused {