Handle FunctionDef blockstart_tolineno edge cases (#2880)

Getting the lineno of the start of the block for function definition(`FunctionDef.blockstart_tolineno`) can be quite tricky. Take below example: ```python # Case A def foo(bar: str) -> None: pass # should returns line=1 # Case B def foo( bar:str): pass # should returns line=2 # Case C def foo( bar:str ) -> None: pass # should returns line=3 # Case D def foo( bar:str ): # should returns line=3 pass ``` Currently we only handled Case A, B. With this commit we can cover case C. But for Case D, we will need a better solution

Author: lowzhao

astroid/nodes/scoped_nodes/scoped_nodes.py

@@ -1401,6 +1401,8 @@ def blockstart_tolineno(self):
 
  :type: int
  """
+ if self.returns:
+ return self.returns.tolineno
  return self.args.tolineno
 
  def implicit_parameters(self) -> Literal[0, 1]:

tests/test_scoped_nodes.py

@@ -982,6 +982,46 @@ def foo():
  with pytest.raises(AttributeInferenceError):
  func.getattr("")
 
+ @staticmethod
+ def test_blockstart_tolineno() -> None:
+ code = textwrap.dedent(
+ """\
+ def f1(bar: str) -> None: #@
+ pass
+
+ def f2( #@
+ bar: str) -> None:
+ pass
+
+ def f3( #@
+ bar: str
+ ) -> None:
+ pass
+
+ def f4( #@
+ bar: str
+ ):
+ pass
+
+ def f5( #@
+ bar: str):
+ pass
+ """
+ )
+ ast_nodes: list[nodes.FunctionDef] = builder.extract_node(code) # type: ignore[assignment]
+ assert len(ast_nodes) == 5
+
+ assert ast_nodes[0].blockstart_tolineno == 1
+
+ assert ast_nodes[1].blockstart_tolineno == 5
+
+ assert ast_nodes[2].blockstart_tolineno == 10
+
+ # Unimplemented, will return line 14 for now.
+ # assert ast_nodes[3].blockstart_tolineno == 15
+
+ assert ast_nodes[4].blockstart_tolineno == 19
+
 
 class ClassNodeTest(ModuleLoader, unittest.TestCase):
  def test_dict_interface(self) -> None: