Tested x86_64-pc-linux-gnu, applying to trunk.
-- 8< --
We assume that a non-"eligible" special member function cannot be selected
by overload resolution, but that isn't the case here due to the difference
in "explicit". So check for that when filtering in add_method.
PR c++/127627
gcc/cp/ChangeLog:
* class.cc (add_method): Don't remove a less-explicit function.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/explicit21.C: New test.
---
gcc/cp/class.cc | 12 +++++++++++-
gcc/testsuite/g++.dg/cpp2a/explicit21.C | 19 +++++++++++++++++++
2 files changed, 30 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/explicit21.C
diff --git a/gcc/cp/class.cc b/gcc/cp/class.cc
index e913a780cdd..f4f2c4aa235 100644
--- a/gcc/cp/class.cc
+++ b/gcc/cp/class.cc
@@ -1418,7 +1418,17 @@ add_method (tree type, tree method, bool via_using)
if (losem || losef)
win = losem - losef;
else
- win = more_constrained (fn, method);
+ {
+ win = more_constrained (fn, method);
+ if (win)
+ {
+ /* The winner can't be more explicit. */
+ int ex = (DECL_NONCONVERTING_P (method)
+ - DECL_NONCONVERTING_P (fn));
+ if (ex && ex != win)
+ win = 0;
+ }
+ }
if (win > 0)
/* Leave FN in the method vec, discard METHOD. */
return false;
diff --git a/gcc/testsuite/g++.dg/cpp2a/explicit21.C
b/gcc/testsuite/g++.dg/cpp2a/explicit21.C
new file mode 100644
index 00000000000..a96a214df67
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/explicit21.C
@@ -0,0 +1,19 @@
+// PR c++/127627
+// { dg-do compile { target c++20 } }
+
+template <class T>
+struct X
+{
+ X() = default;
+ X(const X&) { throw; }
+private:
+ explicit X(const X&) requires (T::value) = default;
+};
+
+struct S { static constexpr bool value = true; };
+
+int main()
+{
+ const X<S> x;
+ X<S> x2 = x;
+}
base-commit: a382bed036aa5f58622fc7551734f6280d1476c9
--
2.55.0
