Actually, one exception to error messages unchanged.

Do we even bother making a special case for this ?

Author: Vanille-N

src/borrow_tracker/tree_borrows/diagnostics.rs

@@ -76,7 +76,14 @@ impl HistoryData {
         );
 
         self.events.push((Some(created.0.data()), msg_creation));
-        for &Event { transition, access_kind, is_foreign, access_range, span, access_subrange: _ } in &events
+        for &Event {
+            transition,
+            access_kind,
+            is_foreign,
+            access_range,
+            span,
+            access_subrange: _,
+        } in &events
         {
             // NOTE: `access_subrange` is explicitly absent from the error message, it has no significance
             // to the user. The meaningful one is `access_range`.
@@ -205,7 +212,9 @@ impl History {
             events: self
                 .events
                 .iter()
-                .filter(|e| e.access_subrange.start <= error_offset && error_offset < e.access_subrange.end)
+                .filter(|e| {
+                    e.access_subrange.start <= error_offset && error_offset < e.access_subrange.end
+                })
                 .cloned()
                 .collect::<Vec<_>>(),
             created: self.created,

src/concurrency/data_race.rs

@@ -859,8 +859,12 @@ impl VClockAlloc {
         if global.race_detecting() {
             let (index, mut clocks) = global.current_thread_state_mut(&machine.threads);
             let mut alloc_ranges = self.alloc_ranges.borrow_mut();
-            for (access_subrange, other_range) in alloc_ranges.iter_mut(access_range.start, access_range.size) {
-                if let Err(DataRace) = other_range.read_race_detect(&mut clocks, index, current_span) {
+            for (access_subrange, other_range) in
+                alloc_ranges.iter_mut(access_range.start, access_range.size)
+            {
+                if let Err(DataRace) =
+                    other_range.read_race_detect(&mut clocks, index, current_span)
+                {
                     drop(clocks);
                     // Report data-race.
                     return Self::report_data_race(
@@ -891,7 +895,9 @@ impl VClockAlloc {
         let global = machine.data_race.as_mut().unwrap();
         if global.race_detecting() {
             let (index, mut clocks) = global.current_thread_state_mut(&machine.threads);
-            for (access_subrange, other_range) in self.alloc_ranges.get_mut().iter_mut(access_range.start, access_range.size) {
+            for (access_subrange, other_range) in
+                self.alloc_ranges.get_mut().iter_mut(access_range.start, access_range.size)
+            {
                 if let Err(DataRace) =
                     other_range.write_race_detect(&mut clocks, index, write_type, current_span)
                 {

tests/fail/tree-borrows/strongly-protected.stderr

@@ -17,6 +17,12 @@ help: the strongly protected tag <TAG> was created here, in the initial state Re
    |
 LL | fn inner(x: &mut i32, f: fn(&mut i32)) {
    |          ^
+help: the strongly protected tag <TAG> then transitioned from Reserved to Active due to a child write access at offsets [0x0..0x4]
+  --> $DIR/strongly-protected.rs:LL:CC
+   |
+LL |         drop(unsafe { Box::from_raw(raw) });
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = help: this corresponds to an activation
    = note: BACKTRACE (of the first span):
    = note: inside `std::alloc::dealloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
    = note: inside `<std::alloc::Global as std::alloc::Allocator>::deallocate` at RUSTLIB/alloc/src/alloc.rs:LL:CC