[gcc r15-8764] gccrs: Fix an issue with ForeverStack::dfs_rib

[Arthur Cohen]

https://gcc.gnu.org/g:c4731c1b144c4219558176f95d2fa3c46df07db2

commit r15-8764-gc4731c1b144c4219558176f95d2fa3c46df07db2
Author: Owen Avery <powerboat9.gamer@gmail.com>
Date:   Fri Jan 31 23:03:03 2025 -0500

    gccrs: Fix an issue with ForeverStack::dfs_rib
    
    gcc/rust/ChangeLog:
    
            * resolve/rust-forever-stack.hxx
            (ForeverStack::dfs_rib): Fix const implementation.
    
    Signed-off-by: Owen Avery <powerboat9.gamer@gmail.com>

Diff:
---
 gcc/rust/resolve/rust-forever-stack.hxx | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/gcc/rust/resolve/rust-forever-stack.hxx b/gcc/rust/resolve/rust-forever-stack.hxx
index 1c83f6bda613..d0d74217b613 100644
--- a/gcc/rust/resolve/rust-forever-stack.hxx
+++ b/gcc/rust/resolve/rust-forever-stack.hxx
@@ -638,9 +638,8 @@ tl::optional<const Rib &>
 ForeverStack<N>::dfs_rib (const ForeverStack<N>::Node &starting_point,
 			  NodeId to_find) const
 {
-  return dfs_node (starting_point, to_find).map ([] (Node &x) -> Rib & {
-    return x.rib;
-  });
+  return dfs_node (starting_point, to_find)
+    .map ([] (const Node &x) -> const Rib & { return x.rib; });
 }
 
 template <Namespace N>