[gcc r17-3396] c++: Fix propagating reference qualifier from function type to member function pointer type [PR70097

https://gcc.gnu.org/g:8f188b67517ce41561295506e3ba01ec1524854a

commit r17-3396-g8f188b67517ce41561295506e3ba01ec1524854a
Author: Eczbek <[email protected]>
Date:   Sun May 24 18:58:09 2026 -0400

    c++: Fix propagating reference qualifier from function type to member function pointer type [PR70097]
    
    When forming a member function pointer type to a ref-qualified function
    type, the reference qualifier is incorrectly dropped.
    
            PR c++/70097
    
    gcc/cp/ChangeLog:
    
            * decl.cc (grokdeclarator): If rqual is REF_QUAL_NONE, set it to
            result of type_memfn_rqual before passing to build_memfn_type.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp0x/ref-qual22.C: New test.

Diff:
---
 gcc/cp/decl.cc                          |  2 ++
 gcc/testsuite/g++.dg/cpp0x/ref-qual22.C | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index cd533217ec40..bd9903c4e739 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -15805,6 +15805,8 @@ grokdeclarator (const cp_declarator *declarator,
 	      && TREE_CODE (type) == FUNCTION_TYPE)
 	    {
 	      memfn_quals |= type_memfn_quals (type);
+	      if (rqual == REF_QUAL_NONE)
+		rqual = type_memfn_rqual (type);
 	      type = build_memfn_type (type,
 				       declarator->u.pointer.class_type,
 				       memfn_quals,
diff --git a/gcc/testsuite/g++.dg/cpp0x/ref-qual22.C b/gcc/testsuite/g++.dg/cpp0x/ref-qual22.C
new file mode 100644
index 000000000000..4859d20053bf
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/ref-qual22.C
@@ -0,0 +1,18 @@
+// PR c++/70097
+// { dg-do compile { target c++11 } }
+
+struct T {
+	void f() & {}
+	void g() && {}
+};
+using F = void() &;
+using G = void() &&;
+
+F T::* f = &T::f;
+G T::* g = &T::g;
+
+template<typename> struct U;
+template<> struct U<void(T::*)() &> {};
+template<> struct U<void(T::*)() &&> {};
+U<F T::*> u;
+U<G T::*> v;