c++: PMF template parm and noexcept [PR90664]

The constexpr code only wants to preserve PTRMEM_CST in conversions if the
conversions are only qualification conversions; dropping noexcept counts as
a qualification adjustment in overload resolution, so let's include it here.

gcc/cp/ChangeLog:

	PR c++/90664
	* cvt.c (can_convert_qual): Check fnptr_conv_p.

gcc/testsuite/ChangeLog:

	PR c++/90664
	* g++.dg/cpp1z/noexcept-type24.C: New test.

2 files changed, 27 insertions, 0 deletions

diff --git a/gcc/cp/cvt.c b/gcc/cp/cvt.c
index d105113..f1687e8 100644
--- a/gcc/cp/cvt.c
+++ b/gcc/cp/cvt.c
@@ -2013,6 +2013,11 @@ can_convert_qual (tree type, tree expr)
   tree expr_type = TREE_TYPE (expr);
   gcc_assert (!same_type_p (type, expr_type));
 
+  /* A function pointer conversion also counts as a Qualification Adjustment
+     under [over.ics.scs].  */
+  if (fnptr_conv_p (type, expr_type))
+    return true;
+
   if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type))
     return comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type));
   else if (TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (expr_type))
diff --git a/gcc/testsuite/g++.dg/cpp1z/noexcept-type24.C b/gcc/testsuite/g++.dg/cpp1z/noexcept-type24.C
new file mode 100644
index 0000000..df16ea7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/noexcept-type24.C
@@ -0,0 +1,22 @@
+// PR c++/90664
+// { dg-do compile { target c++11 } }
+
+template <typename TT, typename MFP, MFP> struct OpM;
+
+template <typename TR, typename TT, TR (TT::*f)()>
+struct OpM<TT, TR (TT::*)(), f>
+{};
+
+class Class {
+public:
+  int address() noexcept { return 0; }
+  void address(int) noexcept {}
+};
+
+struct Sk {
+  template <class C, typename R> Sk(R (C::*p)()) {
+    typedef OpM<C, R (C::*)() /* noexcept */, &Class::address> OP;
+  }
+};
+
+Sk sk(static_cast<int (Class::*)()>(&Class::address));