From 21c688af86a52cf5d44c69c274179e7410e01a49 Mon Sep 17 00:00:00 2001
From: Urgau <urgau@numericable.fr>
Date: Fri, 26 Apr 2024 21:14:37 +0200
Subject: [PATCH] Consider inner modules to be local in the
 `non_local_definitions` lint

---
 compiler/rustc_lint/src/non_local_def.rs      | 16 +++++---
 .../ui/lint/non-local-defs/module_as_local.rs | 38 +++++++++++++++++++
 2 files changed, 49 insertions(+), 5 deletions(-)
 create mode 100644 tests/ui/lint/non-local-defs/module_as_local.rs

diff --git a/compiler/rustc_lint/src/non_local_def.rs b/compiler/rustc_lint/src/non_local_def.rs
index 004c2c2e4f44f..3ab15a5be5888 100644
--- a/compiler/rustc_lint/src/non_local_def.rs
+++ b/compiler/rustc_lint/src/non_local_def.rs
@@ -356,7 +356,7 @@ fn path_has_local_parent(
 }
 
 /// Given a def id and a parent impl def id, this checks if the parent
-/// def id correspond to the def id of the parent impl definition.
+/// def id (modulo modules) correspond to the def id of the parent impl definition.
 #[inline]
 fn did_has_local_parent(
     did: DefId,
@@ -364,8 +364,14 @@ fn did_has_local_parent(
     impl_parent: DefId,
     impl_parent_parent: Option<DefId>,
 ) -> bool {
-    did.is_local() && {
-        let res_parent = tcx.parent(did);
-        res_parent == impl_parent || Some(res_parent) == impl_parent_parent
-    }
+    did.is_local()
+        && if let Some(did_parent) = tcx.opt_parent(did) {
+            did_parent == impl_parent
+                || Some(did_parent) == impl_parent_parent
+                || !did_parent.is_crate_root()
+                    && tcx.def_kind(did_parent) == DefKind::Mod
+                    && did_has_local_parent(did_parent, tcx, impl_parent, impl_parent_parent)
+        } else {
+            false
+        }
 }
diff --git a/tests/ui/lint/non-local-defs/module_as_local.rs b/tests/ui/lint/non-local-defs/module_as_local.rs
new file mode 100644
index 0000000000000..bb215026c7d40
--- /dev/null
+++ b/tests/ui/lint/non-local-defs/module_as_local.rs
@@ -0,0 +1,38 @@
+//! This test checks that module are treated as if they were local
+//!
+//! https://github.com/rust-lang/rust/issues/124396
+
+//@ check-pass
+
+trait JoinTo {}
+
+fn simple_one() {
+    mod posts {
+        #[allow(non_camel_case_types)]
+        pub struct table {}
+    }
+
+    impl JoinTo for posts::table {}
+}
+
+fn simple_two() {
+    mod posts {
+        pub mod posts {
+            #[allow(non_camel_case_types)]
+            pub struct table {}
+        }
+    }
+
+    impl JoinTo for posts::posts::table {}
+}
+
+struct Global;
+fn trait_() {
+    mod posts {
+        pub trait AdjecentTo {}
+    }
+
+    impl posts::AdjecentTo for Global {}
+}
+
+fn main() {}