WIP: fix overzealous filtering of FunctionDef nodes in ClassDef.igetattr

Ref pylint-dev#1015. When there are multiple statements defining some attribute
ClassDef.igetattr filters out later definitions if they are not in the
same scope as the first (to support cases like "self.a = 1; self.a = 2"
or "self.items = []; self.items += 1"). However, it checks the scope of
the first attribute against the *parent scope* of the later attributes.
For mundane statements this makes no difference, but for
scope-introducing statements such as FunctionDef these are not the same.

astroid/nodes/scoped_nodes.py

@@ -2612,7 +2612,7 @@ def igetattr(self, name, context=None, class_context=True):
             # to the attribute happening *after* the attribute's definition (e.g. AugAssigns on lists)
             if len(attributes) > 1:
                 first_attr, attributes = attributes[0], attributes[1:]
-                first_scope = first_attr.scope()
+                first_scope = first_attr.parent.scope()
                 attributes = [first_attr] + [
                     attr
                     for attr in attributes

tests/unittest_inference.py

@@ -51,7 +51,7 @@
 from astroid import decorators as decoratorsmod
 from astroid import helpers, nodes, objects, test_utils, util
 from astroid.arguments import CallSite
-from astroid.bases import BoundMethod, Instance, UnboundMethod
+from astroid.bases import BoundMethod, Generator, Instance, UnboundMethod
 from astroid.builder import AstroidBuilder, extract_node, parse
 from astroid.const import PY38_PLUS, PY39_PLUS
 from astroid.context import InferenceContext
@@ -4005,6 +4005,38 @@ class Test(Outer.Inner):
         assert isinstance(inferred, nodes.Const)
         assert inferred.value == 123
 
+    def test_infer_method_empty_body(self) -> None:
+        # https://github.com/PyCQA/astroid/issues/1015
+        node = extract_node(
+            """
+            class A:
+                def foo(self): ...
+
+            A().foo()  #@
+        """
+        )
+        inferred = next(node.infer())
+        assert isinstance(inferred, nodes.Const)
+        assert inferred.value is None
+
+    def test_infer_method_overload(self) -> None:
+        # https://github.com/PyCQA/astroid/issues/1015
+        node = extract_node(
+            """
+            class A:
+                def foo(self): ...
+
+                def foo(self):
+                    yield
+
+            A().foo()  #@
+        """
+        )
+        inferred = list(node.infer())
+        assert len(inferred) == 2
+        assert isinstance(inferred[0], nodes.Const)
+        assert isinstance(inferred[1], Generator)
+
     def test_delayed_attributes_without_slots(self) -> None:
         ast_node = extract_node(
             """