Fix crash related to functools.total_ordering and forward reference (#12767)

Run the plugin in a later pass to avoid placeholder nodes.

Fixes #11728.

Author: JukkaL

mypy/plugins/default.py

@@ -96,7 +96,6 @@ def get_class_decorator_hook(self, fullname: str
                                  ) -> Optional[Callable[[ClassDefContext], None]]:
         from mypy.plugins import attrs
         from mypy.plugins import dataclasses
-        from mypy.plugins import functools
 
         if fullname in attrs.attr_class_makers:
             return attrs.attr_class_maker_callback
@@ -118,17 +117,18 @@ def get_class_decorator_hook(self, fullname: str
             )
         elif fullname in dataclasses.dataclass_makers:
             return dataclasses.dataclass_tag_callback
-        elif fullname in functools.functools_total_ordering_makers:
-            return functools.functools_total_ordering_maker_callback
 
         return None
 
     def get_class_decorator_hook_2(self, fullname: str
                                    ) -> Optional[Callable[[ClassDefContext], bool]]:
         from mypy.plugins import dataclasses
+        from mypy.plugins import functools
 
         if fullname in dataclasses.dataclass_makers:
             return dataclasses.dataclass_class_maker_callback
+        elif fullname in functools.functools_total_ordering_makers:
+            return functools.functools_total_ordering_maker_callback
 
         return None
 

mypy/plugins/functools.py

@@ -26,25 +26,25 @@ class _MethodInfo(NamedTuple):
 
 
 def functools_total_ordering_maker_callback(ctx: mypy.plugin.ClassDefContext,
-                                            auto_attribs_default: bool = False) -> None:
+                                            auto_attribs_default: bool = False) -> bool:
     """Add dunder methods to classes decorated with functools.total_ordering."""
     if ctx.api.options.python_version < (3,):
         # This plugin is not supported in Python 2 mode (it's a no-op).
-        return
+        return True
 
     comparison_methods = _analyze_class(ctx)
     if not comparison_methods:
         ctx.api.fail(
             'No ordering operation defined when using "functools.total_ordering": < > <= >=',
             ctx.reason)
-        return
+        return True
 
     # prefer __lt__ to __le__ to __gt__ to __ge__
     root = max(comparison_methods, key=lambda k: (comparison_methods[k] is None, k))
     root_method = comparison_methods[root]
     if not root_method:
         # None of the defined comparison methods can be analysed
-        return
+        return True
 
     other_type = _find_other_type(root_method)
     bool_type = ctx.api.named_type('builtins.bool')
@@ -61,6 +61,8 @@ def functools_total_ordering_maker_callback(ctx: mypy.plugin.ClassDefContext,
             args = [Argument(Var('other', other_type), other_type, None, ARG_POS)]
             add_method_to_class(ctx.api, ctx.cls, additional_op, args, ret_type)
 
+    return True
+
 
 def _find_other_type(method: _MethodInfo) -> Type:
     """Find the type of the ``other`` argument in a comparison method."""

test-data/unit/check-functools.test

@@ -132,3 +132,24 @@ from typing import TypeVar, Generic
 _T = TypeVar('_T')
 class cached_property(Generic[_T]): ...
 [builtins fixtures/property.pyi]
+
+[case testTotalOrderingWithForwardReference]
+from typing import Generic, Any, TypeVar
+import functools
+
+T = TypeVar("T", bound="C")
+
+@functools.total_ordering
+class D(Generic[T]):
+    def __lt__(self, other: Any) -> bool:
+        ...
+
+class C:
+    pass
+
+def f(d: D[C]) -> None:
+    reveal_type(d.__gt__)  # N: Revealed type is "def (other: Any) -> builtins.bool"
+
+d: D[int]  # E: Type argument "int" of "D" must be a subtype of "C"
+[builtins fixtures/ops.pyi]
+[builtins fixtures/dict.pyi]