[gcc r9-10167] c++: PMF template parm and noexcept [PR90664]

[gcc r9-10167] c++: PMF template parm and noexcept [PR90664]

[Jason Merrill]

https://gcc.gnu.org/g:45fb36bf93a7cc6506c2a12f9c4aa3981f4e6b44

commit r9-10167-g45fb36bf93a7cc6506c2a12f9c4aa3981f4e6b44
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Apr 2 17:07:12 2021 -0400

    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.

Diff:
---
 gcc/cp/cvt.c                                 |  5 +++++
 gcc/testsuite/g++.dg/cpp1z/noexcept-type24.C | 22 ++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/gcc/cp/cvt.c b/gcc/cp/cvt.c
index 3b8656c2a6b..c2bad5eb43d 100644
--- a/gcc/cp/cvt.c
+++ b/gcc/cp/cvt.c
@@ -1960,6 +1960,11 @@ 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 00000000000..df16ea78641
--- /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));