On 6/22/26 12:08 PM, Marek Polacek wrote:
On Fri, Jun 19, 2026 at 01:44:23PM -0400, Jason Merrill wrote:
On 6/18/26 6:09 PM, Marek Polacek wrote:
FWIW, Jakub seems to agree with this patch in the PR.

Tested reflect/* on x86_64-pc-linux-gnu, ok for trunk/16?

-- >8 --
members_of doesn't append the call operator of a closure type
to ELTS in class_members_of and so the assert in the test doesn't
pass.

        PR c++/125889

gcc/cp/ChangeLog:

        * reflect.cc (class_members_of): Also append LAMBDA_FUNCTION_P
        from the implicitly_declared vector.

gcc/testsuite/ChangeLog:

        * g++.dg/reflect/members_of16.C: New test.
---
   gcc/cp/reflect.cc                           | 7 +++++++
   gcc/testsuite/g++.dg/reflect/members_of16.C | 8 ++++++++
   2 files changed, 15 insertions(+)
   create mode 100644 gcc/testsuite/g++.dg/reflect/members_of16.C

diff --git a/gcc/cp/reflect.cc b/gcc/cp/reflect.cc
index 8dccf5e99a0..f15be65c246 100644
--- a/gcc/cp/reflect.cc
+++ b/gcc/cp/reflect.cc
@@ -7077,6 +7077,13 @@ class_members_of (location_t loc, const constexpr_ctx 
*ctx, tree r,
                                    get_reflection_raw (loc, m));
            break;
          }
+      for (tree m : implicitly_declared)
+       if (LAMBDA_FUNCTION_P (m))
+         {
+           CONSTRUCTOR_APPEND_ELT (elts, NULL_TREE,
+                                   get_reflection_raw (loc, m));
+           break;
+         }
       }
     return elts;
   }
diff --git a/gcc/testsuite/g++.dg/reflect/members_of16.C 
b/gcc/testsuite/g++.dg/reflect/members_of16.C
new file mode 100644
index 00000000000..f23d979e639
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/members_of16.C
@@ -0,0 +1,8 @@
+// PR c++/125889
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection" }
+
+#include <meta>
+
+using L = decltype([]{});
+static_assert(std::meta::members_of(^^L, 
std::meta::access_context::unchecked()).size() > 0);

It seems desirable to check specifically for the call operator, since "It is
implementation-defined whether declarations of other members of a closure
type Q are Q-members-of-eligible."

I can check if we have meta::is_operator_function.  Or do you want me
to check something else as well?

Under the above quote it doesn't seem portable to assume the call operator is at index 0, but I guess it's OK with a comment.

Incidentally, I'm surprised the standard doesn't specify that the conversion function (https://eel.is/c++draft/expr.prim#lambda.closure-11) is members-of-eligible.
-- >8 --
members_of doesn't append the call operator of a closure type
to ELTS in class_members_of and so the assert in the test doesn't
pass.

        PR c++/125889

gcc/cp/ChangeLog:

        * reflect.cc (class_members_of): Also append LAMBDA_FUNCTION_P
        from the implicitly_declared vector.

gcc/testsuite/ChangeLog:

        * g++.dg/reflect/members_of16.C: New test.
---
  gcc/cp/reflect.cc                           | 7 +++++++
  gcc/testsuite/g++.dg/reflect/members_of16.C | 9 +++++++++
  2 files changed, 16 insertions(+)
  create mode 100644 gcc/testsuite/g++.dg/reflect/members_of16.C

diff --git a/gcc/cp/reflect.cc b/gcc/cp/reflect.cc
index 8dccf5e99a0..f15be65c246 100644
--- a/gcc/cp/reflect.cc
+++ b/gcc/cp/reflect.cc
@@ -7077,6 +7077,13 @@ class_members_of (location_t loc, const constexpr_ctx 
*ctx, tree r,
                                    get_reflection_raw (loc, m));
            break;
          }
+      for (tree m : implicitly_declared)
+       if (LAMBDA_FUNCTION_P (m))
+         {
+           CONSTRUCTOR_APPEND_ELT (elts, NULL_TREE,
+                                   get_reflection_raw (loc, m));
+           break;
+         }
      }
    return elts;
  }
diff --git a/gcc/testsuite/g++.dg/reflect/members_of16.C 
b/gcc/testsuite/g++.dg/reflect/members_of16.C
new file mode 100644
index 00000000000..e20c4506825
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/members_of16.C
@@ -0,0 +1,9 @@
+// PR c++/125889
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection" }
+
+#include <meta>
+
+using L = decltype([]{});
+static_assert(members_of(^^L, std::meta::access_context::unchecked()).size() > 
0);
+static_assert(is_operator_function(members_of(^^L, 
std::meta::access_context::unchecked())[0]));

base-commit: 2918eed569574b0c2136256b9898a3287135a899

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