Add enter_trace_span!() that checks if tracing is enabled

1 files changed, 19 insertions, 0 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/util.rs b/compiler/rustc_const_eval/src/interpret/util.rs
index ba579e25f03..847905e8343 100644
--- a/compiler/rustc_const_eval/src/interpret/util.rs
+++ b/compiler/rustc_const_eval/src/interpret/util.rs
@@ -45,3 +45,22 @@ pub(crate) fn create_static_alloc<'tcx>(
     assert!(ecx.memory.alloc_map.insert(alloc_id, (MemoryKind::Stack, alloc)).is_none());
     interp_ok(ecx.ptr_to_mplace(Pointer::from(alloc_id).into(), layout))
 }
+
+/// This struct is needed to enforce `#[must_use]` on [tracing::span::EnteredSpan]
+/// while wrapping them in an `Option`.
+#[must_use]
+pub enum MaybeEnteredSpan {
+    Some(tracing::span::EnteredSpan),
+    None,
+}
+
+#[macro_export]
+macro_rules! enter_trace_span {
+    ($machine:ident, $($tt:tt)*) => {
+        if $machine::TRACING_ENABLED {
+            $crate::interpret::tracing_utils::MaybeEnteredSpan::Some(tracing::info_span!($($tt)*).entered())
+        } else {
+            $crate::interpret::tracing_utils::MaybeEnteredSpan::None
+        }
+    }
+}