bugfix: allow noexcept lambdas in CPP17. Fix #4565

Author: Skylion007

include/pybind11/detail/common.h

@@ -754,7 +754,16 @@ template <typename C, typename R, typename... A>
 struct remove_class<R (C::*)(A...) const> {
     using type = R(A...);
 };
-
+#ifdef __cpp_noexcept_function_type
+template <typename C, typename R, typename... A>
+struct remove_class<R (C::*)(A...) noexcept> {
+    using type = R(A...);
+};
+template <typename C, typename R, typename... A>
+struct remove_class<R (C::*)(A...) const noexcept> {
+    using type = R(A...);
+};
+#endif
 /// Helper template to strip away type modifiers
 template <typename T>
 struct intrinsic_type {

tests/test_constants_and_functions.cpp

@@ -148,4 +148,14 @@ TEST_SUBMODULE(constants_and_functions, m) {
             py::arg_v("y", 42, "<the answer>"),
             py::arg_v("z", default_value));
     });
+
+    // test noexcept(true) lambda
+    m.def("l1", [](void) noexcept(true) {
+        try {
+        } catch (py::error_already_set &eas) {
+            eas.discard_as_unraisable(__func__);
+        } catch (const std::exception &e) {
+        }
+        return 0;
+    });
 }

tests/test_constants_and_functions.py

@@ -50,3 +50,7 @@ def __repr__(self):
         m.register_large_capture_with_invalid_arguments(m)
     with pytest.raises(RuntimeError):
         m.register_with_raising_repr(m, RaisingRepr())
+
+
+def test_noexcept_lambda():
+    assert m.l1() == 0