Remove is_function_or_class helper footgun (#4133)

This is a no-op change.

That function was not a good way to tell if something is a function or a
class, since it basically only worked for async functions by accident
(the parent of a suite / simple_stmt of async function body is a
funcdef).

src/black/linegen.py

@@ -42,12 +42,12 @@
     is_atom_with_invisible_parens,
     is_docstring,
     is_empty_tuple,
-    is_function_or_class,
     is_lpar_token,
     is_multiline_string,
     is_name_token,
     is_one_sequence_between,
     is_one_tuple,
+    is_parent_function_or_class,
     is_rpar_token,
     is_stub_body,
     is_stub_suite,
@@ -302,7 +302,7 @@ def visit_simple_stmt(self, node: Node) -> Iterator[Line]:
 
         if node.parent and node.parent.type in STATEMENT:
             if Preview.dummy_implementations in self.mode:
-                condition = is_function_or_class(node.parent)
+                condition = is_parent_function_or_class(node)
             else:
                 condition = self.mode.is_pyi
             if condition and is_stub_body(node):

src/black/nodes.py

@@ -742,6 +742,13 @@ def is_multiline_string(leaf: Leaf) -> bool:
     return has_triple_quotes(leaf.value) and "\n" in leaf.value
 
 
+def is_parent_function_or_class(node: Node) -> bool:
+    assert node.type in {syms.suite, syms.simple_stmt}
+    assert node.parent is not None
+    # Note this works for suites / simple_stmts in async def as well
+    return node.parent.type in {syms.funcdef, syms.classdef}
+
+
 def is_function_or_class(node: Node) -> bool:
     return node.type in {syms.funcdef, syms.classdef, syms.async_funcdef}
 
@@ -751,7 +758,7 @@ def is_stub_suite(node: Node, mode: Mode) -> bool:
     if (
         node.parent is not None
         and Preview.dummy_implementations in mode
-        and not is_function_or_class(node.parent)
+        and not is_parent_function_or_class(node)
     ):
         return False
 

tests/data/cases/preview_dummy_implementations.py

@@ -58,6 +58,17 @@ def has_comment():
 
 if already_dummy: ...
 
+class AsyncCls:
+    async def async_method(self):
+        ...
+
+async def async_function(self):
+    ...
+
+@decorated
+async def async_function(self):
+    ...
+
 # output
 
 from typing import NoReturn, Protocol, Union, overload
@@ -121,3 +132,14 @@ def has_comment(): ...  # still a dummy
 
 if already_dummy:
     ...
+
+
+class AsyncCls:
+    async def async_method(self): ...
+
+
+async def async_function(self): ...
+
+
+@decorated
+async def async_function(self): ...