1 files changed, 29 insertions, 0 deletions
diff --git a/tests/coverage/no_spans.rs b/tests/coverage/no_spans.rs
new file mode 100644
index 000000000..a5234bc6b
--- /dev/null
+++ b/tests/coverage/no_spans.rs
@@ -0,0 +1,29 @@
+#![feature(coverage_attribute)]
+// edition: 2021
+
+// If the span extractor can't find any relevant spans for a function, the
+// refinement loop will terminate with nothing in its `prev` slot. If the
+// subsequent code tries to unwrap `prev`, it will panic.
+//
+// This scenario became more likely after #118525 started discarding spans that
+// can't be un-expanded back to within the function body.
+//
+// Regression test for "invalid attempt to unwrap a None some_prev", as seen
+// in issues such as #118643 and #118662.
+
+#[coverage(off)]
+fn main() {
+    affected_function()();
+}
+
+macro_rules! macro_that_defines_a_function {
+    (fn $name:ident () $body:tt) => {
+        fn $name () -> impl Fn() $body
+    }
+}
+
+macro_that_defines_a_function! {
+    fn affected_function() {
+        || ()
+    }
+}