[gcc r14-8533] gccrs: foreverstack: Specialize `get` for Namespace::Labels

[Arthur Cohen]

https://gcc.gnu.org/g:eec00ae27522438d6021c01501489cada87812dc

commit r14-8533-geec00ae27522438d6021c01501489cada87812dc
Author: Arthur Cohen <arthur.cohen@embecosm.com>
Date:   Mon Aug 21 16:05:22 2023 +0200

    gccrs: foreverstack: Specialize `get` for Namespace::Labels
    
    gcc/rust/ChangeLog:
    
            * resolve/rust-forever-stack.hxx: Add specific behavior for
            `ForeverStack::get` when dealing with labels.

Diff:
---
 gcc/rust/resolve/rust-forever-stack.hxx | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/gcc/rust/resolve/rust-forever-stack.hxx b/gcc/rust/resolve/rust-forever-stack.hxx
index 806745eb9081..211979fa9b95 100644
--- a/gcc/rust/resolve/rust-forever-stack.hxx
+++ b/gcc/rust/resolve/rust-forever-stack.hxx
@@ -208,7 +208,7 @@ ForeverStack<N>::update_cursor (Node &new_cursor)
 }
 
 template <Namespace N>
-inline tl::optional<NodeId>
+tl::optional<NodeId>
 ForeverStack<N>::get (const Identifier &name)
 {
   tl::optional<NodeId> resolved_node = tl::nullopt;
@@ -234,6 +234,33 @@ ForeverStack<N>::get (const Identifier &name)
   return resolved_node;
 }
 
+template <>
+tl::optional<NodeId> inline ForeverStack<Namespace::Labels>::get (
+  const Identifier &name)
+{
+  tl::optional<NodeId> resolved_node = tl::nullopt;
+
+  reverse_iter ([&resolved_node, &name] (Node &current) {
+    // looking up for labels cannot go through function ribs
+    // TODO: What other ribs?
+    if (current.rib.kind == Rib::Kind::Function)
+      return KeepGoing::No;
+
+    auto candidate = current.rib.get (name.as_string ());
+
+    // FIXME: Factor this in a function with the generic `get`
+    return candidate.map_or (
+      [&resolved_node] (NodeId found) {
+	resolved_node = found;
+
+	return KeepGoing::No;
+      },
+      KeepGoing::Yes);
+  });
+
+  return resolved_node;
+}
+
 /* Check if an iterator points to the last element */
 template <typename I, typename C>
 static bool