add regression test for #97589

tests/ui/parser/issues/circular-module-with-doc-comment-issue-97589/circular-module-with-doc-comment-issue-97589.rs

@@ -0,0 +1,6 @@
+//@ error-pattern: circular modules
+// Regression test for #97589: a doc-comment on a circular module bypassed cycle detection
+
+#![crate_type = "lib"]
+
+pub mod recursive;

tests/ui/parser/issues/circular-module-with-doc-comment-issue-97589/circular-module-with-doc-comment-issue-97589.stderr

@@ -0,0 +1,8 @@
+error: circular modules: $DIR/recursive.rs -> $DIR/recursive.rs
+  --> $DIR/recursive.rs:6:1
+   |
+LL | mod recursive;
+   | ^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/parser/issues/circular-module-with-doc-comment-issue-97589/recursive.rs

@@ -0,0 +1,6 @@
+//@ ignore-test: this is an auxiliary file for circular-module-with-doc-comment-issue-97589.rs
+
+//! this comment caused the circular dependency checker to break
+
+#[path = "recursive.rs"]
+mod recursive;