[gcc r12-7852] c++: member alias declaration [PR103968]

[Jason Merrill <jason@gcc.gnu.org>]

https://gcc.gnu.org/g:c7361eb36fa50307c9f7cfca36c9f58ce24f8f54

commit r12-7852-gc7361eb36fa50307c9f7cfca36c9f58ce24f8f54
Author: Jason Merrill <jason@redhat.com>
Date:   Sun Mar 27 00:28:30 2022 -0400

    c++: member alias declaration [PR103968]
    
    Here, we were wrongly thinking that (const Options&)Widget<T>::c_options is
    not value-dependent because neither the type nor the (value of) c_options
    are dependent, but since we're binding it to a reference we also need to
    consider that it has a value-dependent address.
    
            PR c++/103968
    
    gcc/cp/ChangeLog:
    
            * pt.cc (value_dependent_expression_p): Check
            has_value_dependent_address for conversion to reference.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp0x/alias-decl-mem1.C: New test.

Diff:
---
 gcc/cp/pt.cc                                 |  4 ++++
 gcc/testsuite/g++.dg/cpp0x/alias-decl-mem1.C | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index b229c9fc739..41f1ef1f64d 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -27449,6 +27449,10 @@ value_dependent_expression_p (tree expression)
 	if (TREE_CODE (expression) == TREE_LIST)
 	  return any_value_dependent_elements_p (expression);
 
+	if (TREE_CODE (type) == REFERENCE_TYPE
+	    && has_value_dependent_address (expression))
+	  return true;
+
 	return value_dependent_expression_p (expression);
       }
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-mem1.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-mem1.C
new file mode 100644
index 00000000000..3e422de4054
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-mem1.C
@@ -0,0 +1,20 @@
+// PR c++/103968
+// { dg-do compile { target c++11 } }
+
+template <typename Opt, Opt const& options>
+struct trait
+{
+    template <typename T>
+    struct NonInstantiated{};
+};
+
+struct Options {};
+
+template <typename T>
+struct Widget
+{
+    static constexpr auto c_options = Options{};
+    using Trait = trait<decltype(c_options), c_options>;
+};
+
+Widget<int>::Trait b{}; // Crashes GCC > 10.3