Rollup merge of #69960 - RalfJung:abort, r=oli-obk

miri engine: fix treatment of abort intrinsic

I screwed up in #69830 and added `abort` to the wrong block of intrinsics, namely the one that actually has a return place. So that branch was never actually reached.

r? @oli-obk

Author: JohnTitor

src/librustc_mir/interpret/intrinsics.rs

@@ -84,14 +84,15 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let substs = instance.substs;
         let intrinsic_name = self.tcx.item_name(instance.def_id());
 
-        // We currently do not handle any intrinsics that are *allowed* to diverge,
-        // but `transmute` could lack a return place in case of UB.
+        // First handle intrinsics without return place.
         let (dest, ret) = match ret {
-            Some(p) => p,
             None => match intrinsic_name {
-                sym::transmute => throw_ub!(Unreachable),
+                sym::transmute => throw_ub_format!("transmuting to uninhabited type"),
+                sym::abort => M::abort(self)?,
+                // Unsupported diverging intrinsic.
                 _ => return Ok(false),
             },
+            Some(p) => p,
         };
 
         // Keep the patterns in this match ordered the same as the list in
@@ -103,10 +104,6 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 self.write_scalar(location.ptr, dest)?;
             }
 
-            sym::abort => {
-                M::abort(self)?;
-            }
-
             sym::min_align_of
             | sym::pref_align_of
             | sym::needs_drop

src/test/ui/consts/const-eval/validate_uninhabited_zsts.stderr

@@ -4,7 +4,7 @@ warning: any use of this value will cause an error
 LL |     unsafe { std::mem::transmute(()) }
    |              ^^^^^^^^^^^^^^^^^^^^^^^
    |              |
-   |              entering unreachable code
+   |              transmuting to uninhabited type
    |              inside call to `foo` at $DIR/validate_uninhabited_zsts.rs:14:26
 ...
 LL | const FOO: [Empty; 3] = [foo(); 3];