tweak Box retag diagnostics

Author: RalfJung

src/tools/miri/src/borrow_tracker/stacked_borrows/diagnostics.rs

@@ -86,12 +86,7 @@ impl fmt::Display for InvalidationCause {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             InvalidationCause::Access(kind) => write!(f, "{kind}"),
-            InvalidationCause::Retag(perm, kind) =>
-                if *kind == RetagCause::FnEntry {
-                    write!(f, "{perm:?} FnEntry retag")
-                } else {
-                    write!(f, "{perm:?} retag")
-                },
+            InvalidationCause::Retag(perm, kind) => write!(f, "{perm:?} {retag}", retag = kind.summary()),
         }
     }
 }
@@ -192,6 +187,7 @@ struct RetagOp {
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub enum RetagCause {
     Normal,
+    Box,
     FnReturnPlace,
     FnEntry,
     TwoPhase,
@@ -490,6 +486,7 @@ impl RetagCause {
     fn summary(&self) -> String {
         match self {
             RetagCause::Normal => "retag",
+            RetagCause::Box => "Box retag",
             RetagCause::FnEntry => "FnEntry retag",
             RetagCause::FnReturnPlace => "return-place retag",
             RetagCause::TwoPhase => "two-phase retag",

src/tools/miri/src/borrow_tracker/stacked_borrows/mod.rs

@@ -221,6 +221,7 @@ impl<'tcx> Stack {
         if !global.tracked_pointer_tags.is_empty() {
             dcx.check_tracked_tag_popped(item, global);
         }
+        dcx.log_invalidation(item.tag());
 
         if !item.protected() {
             return Ok(());
@@ -281,7 +282,6 @@ impl<'tcx> Stack {
             };
             self.pop_items_after(first_incompatible_idx, |item| {
                 Stack::item_invalidated(&item, global, dcx)?;
-                dcx.log_invalidation(item.tag());
                 Ok(())
             })?;
         } else {
@@ -302,7 +302,6 @@ impl<'tcx> Stack {
             };
             self.disable_uniques_starting_at(first_incompatible_idx, |item| {
                 Stack::item_invalidated(&item, global, dcx)?;
-                dcx.log_invalidation(item.tag());
                 Ok(())
             })?;
         }
@@ -928,7 +927,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                     access: Some(AccessKind::Write),
                     protector: false,
                 };
-                self.retag_ptr_inplace(place, new_perm, self.retag_cause)
+                self.retag_ptr_inplace(place, new_perm, RetagCause::Box)
             }
 
             fn visit_value(&mut self, place: &PlaceTy<'tcx, Provenance>) -> InterpResult<'tcx> {

src/tools/miri/tests/fail/stacked_borrows/box_noalias_violation.stderr

@@ -14,7 +14,7 @@ help: <TAG> was created by a SharedReadOnly retag at offsets [0x0..0x4]
    |
 LL |         let ptr = &*b as *const i32;
    |                   ^^^
-help: <TAG> was later invalidated at offsets [0x0..0x4] by a Unique retag
+help: <TAG> was later invalidated at offsets [0x0..0x4] by a Unique Box retag
   --> $DIR/box_noalias_violation.rs:LL:CC
    |
 LL |         test(b, ptr);

src/tools/miri/tests/fail/stacked_borrows/return-noalias.stderr

@@ -14,6 +14,11 @@ help: <TAG> was created here, as the base tag for ALLOC
    |
 LL |     let b = unsafe { Box::from_raw(&mut m) };
    |                                    ^^^^^^
+help: <TAG> was later invalidated at offsets [0x0..0x4] by a Unique Box retag
+  --> $DIR/return-noalias.rs:LL:CC
+   |
+LL |     let b = unsafe { Box::from_raw(&mut m) };
+   |                      ^^^^^^^^^^^^^^^^^^^^^
    = note: BACKTRACE (of the first span):
    = note: inside `main` at $DIR/return-noalias.rs:LL:CC
    = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)