From aec6f9792cb5a2041ff95950fcc8febb1f21db5e Mon Sep 17 00:00:00 2001
From: Max Siling <root@goldstein.lol>
Date: Mon, 20 Oct 2025 18:18:21 +0300
Subject: [PATCH] Fix ICE in rustdoc when impl is nested in a func

---
 src/librustdoc/html/render/span_map.rs |  7 +++++++
 tests/rustdoc/nested-fn-impl-147882.rs | 22 ++++++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 tests/rustdoc/nested-fn-impl-147882.rs

diff --git a/src/librustdoc/html/render/span_map.rs b/src/librustdoc/html/render/span_map.rs
index bc9417b1bb1de..e99e26a73faa4 100644
--- a/src/librustdoc/html/render/span_map.rs
+++ b/src/librustdoc/html/render/span_map.rs
@@ -251,6 +251,13 @@ fn hir_enclosing_body_owner(tcx: TyCtxt<'_>, hir_id: HirId) -> Option<LocalDefId
             return None;
         } else if let Some((def_id, _)) = node.associated_body() {
             return Some(def_id);
+        // Items don't have enclosing bodies.
+        // If we go any further, we might encounter an enclosing function
+        // (e.g. if we're inside an impl that's inside of a function).
+        // This would cause us to erroneously consider this function to be the owner
+        // of the node and produce invalid `HirId`s later.
+        } else if matches!(node, Node::Item(_)) {
+            return None;
         }
     }
     None
diff --git a/tests/rustdoc/nested-fn-impl-147882.rs b/tests/rustdoc/nested-fn-impl-147882.rs
new file mode 100644
index 0000000000000..68c229f5ffc02
--- /dev/null
+++ b/tests/rustdoc/nested-fn-impl-147882.rs
@@ -0,0 +1,22 @@
+//@ compile-flags: -Zunstable-options --generate-link-to-definition
+
+// See: https://github.com/rust-lang/rust/issues/147882
+
+#![crate_name = "foo"]
+
+trait Fun {
+    fn fun();
+}
+
+trait Other {}
+
+impl Fun for () {
+    fn fun() {
+        impl<E> Other for E
+        where
+            E: std::str::FromStr,
+            E::Err: Send,
+        {
+        }
+    }
+}