Fix __new__ overloads with variadic args but not keyword args. (#1172)

We had confused has_var_kwargs with has_var_args, and this made us think
that such a __new__ overload was not compatible with a nullary call.

Author: hawkinsp

src/nb_func.cpp

@@ -201,8 +201,8 @@ PyObject *nb_func_new(const func_data_prelim_base *f) noexcept {
     bool has_scope       = f->flags & (uint32_t) func_flags::has_scope,
          has_name        = f->flags & (uint32_t) func_flags::has_name,
          has_args        = f->flags & (uint32_t) func_flags::has_args,
-         has_var_args    = f->flags & (uint32_t) func_flags::has_var_kwargs,
-         has_var_kwargs  = f->flags & (uint32_t) func_flags::has_var_args,
+         has_var_args    = f->flags & (uint32_t) func_flags::has_var_args,
+         has_var_kwargs  = f->flags & (uint32_t) func_flags::has_var_kwargs,
          can_mutate_args = f->flags & (uint32_t) func_flags::can_mutate_args,
          has_doc         = f->flags & (uint32_t) func_flags::has_doc,
          has_signature   = f->flags & (uint32_t) func_flags::has_signature,

tests/test_classes.cpp

@@ -680,13 +680,20 @@ NB_MODULE(test_classes_ext, m) {
     // issue #786
     struct NewNone {};
     struct NewDflt { int value; };
+    struct NewStarPosOnly { size_t value; };
     struct NewStar { size_t value; };
     nb::class_<NewNone>(m, "NewNone")
         .def(nb::new_([]() { return NewNone(); }));
     nb::class_<NewDflt>(m, "NewDflt")
         .def(nb::new_([](int value) { return NewDflt{value}; }),
              "value"_a = 42)
         .def_ro("value", &NewDflt::value);
+    nb::class_<NewStarPosOnly>(m, "NewStarPosOnly")
+        .def(nb::new_([](nb::args a, int value) {
+            return NewStarPosOnly{nb::len(a) + value};
+        }),
+            "args"_a, "value"_a = 42)
+        .def_ro("value", &NewStarPosOnly::value);
     nb::class_<NewStar>(m, "NewStar")
         .def(nb::new_([](nb::args a, int value, nb::kwargs k) {
             return NewStar{nb::len(a) + value + 10 * nb::len(k)};

tests/test_classes.py

@@ -895,6 +895,10 @@ def test46_custom_new():
     t.NewNone()
     assert t.NewDflt().value == 42
     assert t.NewDflt(10).value == 10
+    assert t.NewStarPosOnly().value == 42
+    assert t.NewStarPosOnly("hi").value == 43
+    assert t.NewStarPosOnly(value=10).value == 10
+    assert t.NewStarPosOnly("hi", "lo", value=10).value == 12
     assert t.NewStar().value == 42
     assert t.NewStar("hi").value == 43
     assert t.NewStar(value=10).value == 10

tests/test_classes_ext.pyi.ref

@@ -335,6 +335,12 @@ class NewDflt:
     @property
     def value(self) -> int: ...
 
+class NewStarPosOnly:
+    def __init__(self, *args, value: int = 42) -> None: ...
+
+    @property
+    def value(self) -> int: ...
+
 class NewStar:
     def __init__(self, *args, value: int = 42, **kwargs) -> None: ...