Implement __new__ signatures, fixes #2073

jedi/inference/value/klass.py

@@ -378,6 +378,18 @@ class ClassMixin:
                 return sigs
         args = ValuesArguments([])
         init_funcs = self.py__call__(args).py__getattribute__('__init__')
+        if len(init_funcs) == 1:
+            init = next(iter(init_funcs))
+            try:
+                class_context = init.class_context
+            except AttributeError:
+                pass
+            else:
+                # In the case where we are on object.__init__, we try to use
+                # __new__.
+                if class_context.get_root_context().is_builtins_module() \
+                        and init.class_context.name.string_name == "object":
+                    init_funcs = self.py__call__(args).py__getattribute__('__new__')
 
         dataclass_sigs = self._get_dataclass_transform_signatures()
         if dataclass_sigs:

test/test_api/test_call_signatures.py

@@ -27,6 +27,17 @@ def test_valid_call(Script):
     assert_signature(Script, 'bool()', 'bool', column=5)
 
 
+def test_dunder_new(Script):
+    # From #2073
+    s = dedent("""\
+    from typing import Self
+    class C:
+        def __new__(cls, b) -> Self:
+            pass
+    C( )""")
+    assert_signature(Script, s, 'C', 0, line=5, column=2)
+
+
 class TestSignatures(TestCase):
     @pytest.fixture(autouse=True)
     def init(self, Script):