[gcc r14-7977] gccrs: Change trait getter to return references

[Arthur Cohen]

https://gcc.gnu.org/g:90ee631428f0af1d91ee297ea114755d7f0563c7

commit r14-7977-g90ee631428f0af1d91ee297ea114755d7f0563c7
Author: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
Date:   Mon Jul 31 12:31:58 2023 +0200

    gccrs: Change trait getter to return references
    
    Having copy and any other constructor stuff might lead to a breakage in
    the future where the node id differs due to a newly constructed
    SimplePath node. This change will allow us to assert the NodeId is from
    the ast and not any copy made in between.
    
    gcc/rust/ChangeLog:
    
            * ast/rust-ast.cc (Attribute::get_traits_to_derive): Change
            return type to a vector of references.
            * ast/rust-ast.h: Update constructor.
            * expand/rust-expand-visitor.cc (ExpandVisitor::expand_inner_stmts):
            Update function call.
    
    Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

Diff:
---
 gcc/rust/ast/rust-ast.cc               | 6 +++---
 gcc/rust/ast/rust-ast.h                | 2 +-
 gcc/rust/expand/rust-expand-visitor.cc | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/gcc/rust/ast/rust-ast.cc b/gcc/rust/ast/rust-ast.cc
index 076f40e338b..3525a15beb5 100644
--- a/gcc/rust/ast/rust-ast.cc
+++ b/gcc/rust/ast/rust-ast.cc
@@ -95,15 +95,15 @@ Attribute::is_derive () const
  *
  * @param attrs The attributes on the item to derive
  */
-std::vector<AST::SimplePath>
+std::vector<std::reference_wrapper<AST::SimplePath>>
 Attribute::get_traits_to_derive ()
 {
-  std::vector<AST::SimplePath> result;
+  std::vector<std::reference_wrapper<AST::SimplePath>> result;
   auto &input = get_attr_input ();
   switch (input.get_attr_input_type ())
     {
       case AST::AttrInput::META_ITEM: {
-	auto meta = static_cast<AST::AttrInputMetaItemContainer &> (input);
+	auto &meta = static_cast<AST::AttrInputMetaItemContainer &> (input);
 	for (auto &current : meta.get_items ())
 	  {
 	    // HACK: Find a better way to achieve the downcast.
diff --git a/gcc/rust/ast/rust-ast.h b/gcc/rust/ast/rust-ast.h
index 32732ffdbd7..136da86525d 100644
--- a/gcc/rust/ast/rust-ast.h
+++ b/gcc/rust/ast/rust-ast.h
@@ -519,7 +519,7 @@ public:
 
   bool is_derive () const;
 
-  std::vector<AST::SimplePath> get_traits_to_derive ();
+  std::vector<std::reference_wrapper<AST::SimplePath>> get_traits_to_derive ();
 
   // default destructor
   ~Attribute () = default;
diff --git a/gcc/rust/expand/rust-expand-visitor.cc b/gcc/rust/expand/rust-expand-visitor.cc
index f75069b2e0a..55d5de0a04e 100644
--- a/gcc/rust/expand/rust-expand-visitor.cc
+++ b/gcc/rust/expand/rust-expand-visitor.cc
@@ -185,7 +185,7 @@ ExpandVisitor::expand_inner_items (
 		  for (auto &to_derive : traits_to_derive)
 		    {
 		      auto maybe_builtin = MacroBuiltin::builtins.lookup (
-			to_derive.as_string ());
+			to_derive.get ().as_string ());
 		      if (MacroBuiltin::builtins.is_iter_ok (maybe_builtin))
 			{
 			  auto new_item
@@ -271,7 +271,7 @@ ExpandVisitor::expand_inner_stmts (AST::BlockExpr &expr)
 		  for (auto &to_derive : traits_to_derive)
 		    {
 		      auto maybe_builtin = MacroBuiltin::builtins.lookup (
-			to_derive.as_string ());
+			to_derive.get ().as_string ());
 		      if (MacroBuiltin::builtins.is_iter_ok (maybe_builtin))
 			{
 			  auto new_item