Add regression test comment
diff --git a/src/test/rustdoc/fn-bound.rs b/src/test/rustdoc/fn-bound.rs
index d5d5838..4c4ffdd 100644
--- a/src/test/rustdoc/fn-bound.rs
+++ b/src/test/rustdoc/fn-bound.rs
@@ -1,3 +1,5 @@
+// Regression test for #100143
+
 use std::iter::Peekable;
 
 pub struct Span<F: Fn(&i32)> {