Use a reference wrapper to please GCC 4.8

gcc/rust/ChangeLog:

	* backend/rust-compile-expr.cc (CompileExpr::visit): Change call.
	(CompileExpr::resolve_operator_overload): Update function arguments.
	* backend/rust-compile-expr.h: Change the function's prototype to use
	a reference wrapper instead of a reference within the optional.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

2 files changed, 11 insertions, 10 deletions

diff --git a/gcc/rust/backend/rust-compile-expr.cc b/gcc/rust/backend/rust-compile-expr.cc
index c4ae79d..615354f 100644
--- a/gcc/rust/backend/rust-compile-expr.cc
+++ b/gcc/rust/backend/rust-compile-expr.cc
@@ -31,6 +31,7 @@
 #include "convert.h"
 #include "print-tree.h"
 #include "rust-system.h"
+#include <functional>
 
 namespace Rust {
 namespace Compile {
@@ -152,8 +153,9 @@ CompileExpr::visit (HIR::ArithmeticOrLogicalExpr &expr)
     {
       auto lang_item_type
 	= LangItem::OperatorToLangItem (expr.get_expr_type ());
-      translated = resolve_operator_overload (lang_item_type, expr, lhs, rhs,
-					      expr.get_lhs (), expr.get_rhs ());
+      translated = resolve_operator_overload (
+	lang_item_type, expr, lhs, rhs, expr.get_lhs (),
+	tl::optional<std::reference_wrapper<HIR::Expr>> (expr.get_rhs ()));
       return;
     }
 
@@ -1476,10 +1478,9 @@ CompileExpr::get_receiver_from_dyn (const TyTy::DynamicObjectType *dyn,
 }
 
 tree
-CompileExpr::resolve_operator_overload (LangItem::Kind lang_item_type,
-					HIR::OperatorExprMeta expr, tree lhs,
-					tree rhs, HIR::Expr &lhs_expr,
-					tl::optional<HIR::Expr &> rhs_expr)
+CompileExpr::resolve_operator_overload (
+  LangItem::Kind lang_item_type, HIR::OperatorExprMeta expr, tree lhs, tree rhs,
+  HIR::Expr &lhs_expr, tl::optional<std::reference_wrapper<HIR::Expr>> rhs_expr)
 {
   TyTy::FnType *fntype;
   bool is_op_overload = ctx->get_tyctx ()->lookup_operator_overload (
diff --git a/gcc/rust/backend/rust-compile-expr.h b/gcc/rust/backend/rust-compile-expr.h
index 872b510..9e7af42 100644
--- a/gcc/rust/backend/rust-compile-expr.h
+++ b/gcc/rust/backend/rust-compile-expr.h
@@ -96,10 +96,10 @@ protected:
 			      TyTy::BaseType *receiver, TyTy::FnType *fntype,
 			      tree receiver_ref, location_t expr_locus);
 
-  tree resolve_operator_overload (LangItem::Kind lang_item_type,
-				  HIR::OperatorExprMeta expr, tree lhs,
-				  tree rhs, HIR::Expr &lhs_expr,
-				  tl::optional<HIR::Expr &> rhs_expr);
+  tree resolve_operator_overload (
+    LangItem::Kind lang_item_type, HIR::OperatorExprMeta expr, tree lhs,
+    tree rhs, HIR::Expr &lhs_expr,
+    tl::optional<std::reference_wrapper<HIR::Expr>> rhs_expr);
 
   tree compile_bool_literal (const HIR::LiteralExpr &expr,
 			     const TyTy::BaseType *tyty);