From 0154f5c0cac3a384db6743235c060ad8bb1e6079 Mon Sep 17 00:00:00 2001
From: Yap Zhi Heng <yapzhhg@gmail.com>
Date: Sat, 6 Jun 2026 10:56:19 +0800
Subject: [PATCH] gccrs: Search lang_prelude when reaching module boundary
 during name resolution

gcc/rust/ChangeLog:

	* resolve/rust-name-resolution-context.h (NameResolutionContext): Add new function
	definition for `should_search_prelude`.
	* resolve/rust-name-resolution-context.hxx (NameResolutionContext::should_search_prelude):
	Add implementation.
	(NameResolutionContext::resolve_segments): Update the check to trigger lang_prelude search
	during name resolution in modules.

Signed-off-by: Yap Zhi Heng <yapzhhg@gmail.com>
---
 .../resolve/rust-name-resolution-context.h    |  6 +++++
 .../resolve/rust-name-resolution-context.hxx  | 23 ++++++++++++++++++-
 .../rust/compile/name_resolution28.rs         | 11 +++++++++
 3 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/rust/compile/name_resolution28.rs

diff --git a/gcc/rust/resolve/rust-name-resolution-context.h b/gcc/rust/resolve/rust-name-resolution-context.h
index 6cbcfbb7655..3bda8178a83 100644
--- a/gcc/rust/resolve/rust-name-resolution-context.h
+++ b/gcc/rust/resolve/rust-name-resolution-context.h
@@ -872,6 +872,12 @@ class NameResolutionContext
   tl::optional<NodeId> prelude;
 
 private:
+  template <Namespace N>
+  bool
+  should_search_prelude (const typename ForeverStack<N>::Node *current_node,
+			 const typename ForeverStack<N>::SegIterator &iterator,
+			 const std::vector<ResolutionPath::Segment> &segments);
+
   /**
    * Resolve a path to its definition
    *
diff --git a/gcc/rust/resolve/rust-name-resolution-context.hxx b/gcc/rust/resolve/rust-name-resolution-context.hxx
index 359dd9c65e5..7a8f24ac515 100644
--- a/gcc/rust/resolve/rust-name-resolution-context.hxx
+++ b/gcc/rust/resolve/rust-name-resolution-context.hxx
@@ -28,6 +28,26 @@
 namespace Rust {
 namespace Resolver2_0 {
 
+template <Namespace N>
+bool
+NameResolutionContext::should_search_prelude (
+  const typename ForeverStack<N>::Node *current_node,
+  const typename ForeverStack<N>::SegIterator &iterator,
+  const std::vector<ResolutionPath::Segment> &segments)
+{
+  // Check whether the current_node is a root node
+  if (current_node->is_root ())
+    return true;
+
+  // Check whether we're at the start of a module (we can't travel elsewhere
+  // from the start of a module)
+  if (is_start (iterator, segments)
+      && current_node->rib.kind == Rib::Kind::Module)
+    return true;
+
+  return false;
+}
+
 template <Namespace N>
 tl::optional<Rib::Definition>
 NameResolutionContext::resolve_path (
@@ -383,7 +403,8 @@ NameResolutionContext::resolve_segments (
 		}
 	    }
 
-	  if (current_node->is_root () && !searched_prelude)
+	  if (!searched_prelude
+	      && should_search_prelude<N> (current_node, iterator, segments))
 	    {
 	      searched_prelude = true;
 	      current_node = &stack.lang_prelude;
diff --git a/gcc/testsuite/rust/compile/name_resolution28.rs b/gcc/testsuite/rust/compile/name_resolution28.rs
new file mode 100644
index 00000000000..d2400aed4bd
--- /dev/null
+++ b/gcc/testsuite/rust/compile/name_resolution28.rs
@@ -0,0 +1,11 @@
+#![feature(no_core, lang_items)]
+#![no_core]
+
+pub mod lateresolve {
+    #![lang = "f32"]
+    impl f32 {
+        pub const RADIX: u32 = 2;
+    }
+
+    pub const _: u32 = f32::RADIX;
+}