Handle a case when model_config is defined as a model property (#9004)

docs/errors/usage_errors.md

@@ -1089,4 +1089,19 @@ pydantic.errors.PydanticUserError: Dataclass field bar has init=False and init_v
 """
 ```
 
+## `model_config` is used as a model field {#model-config-invalid-field-name}
+
+This error is raised when `model_config` is used as the name of a field.
+```py
+from pydantic import BaseModel, PydanticUserError
+
+try:
+
+    class Model(BaseModel):
+        model_config: str
+
+except PydanticUserError as exc_info:
+    assert exc_info.code == 'model-config-invalid-field-name'
+```
+
 {% endraw %}

pydantic/_internal/_config.py

@@ -116,6 +116,13 @@ def for_model(cls, bases: tuple[type[Any], ...], namespace: dict[str, Any], kwar
         config_class_from_namespace = namespace.get('Config')
         config_dict_from_namespace = namespace.get('model_config')
 
+        raw_annotations = namespace.get('__annotations__', {})
+        if raw_annotations.get('model_config') and not config_dict_from_namespace:
+            raise PydanticUserError(
+                '`model_config` cannot be used as a model field name. Use `model_config` for model configuration.',
+                code='model-config-invalid-field-name',
+            )
+
         if config_class_from_namespace and config_dict_from_namespace:
             raise PydanticUserError('"Config" and "model_config" cannot be used together', code='config-both')
 

pydantic/errors.py

@@ -61,6 +61,7 @@
     'unevaluable-type-annotation',
     'dataclass-init-false-extra-allow',
     'clashing-init-and-init-var',
+    'model-config-invalid-field-name',
 ]
 
 

tests/test_config.py

@@ -796,3 +796,26 @@ def create_partial(model, optionals):
 
     # AssertionError: assert ['a', 'b'] == ['b']
     assert partial.model_json_schema()['required'] == ['b']
+
+
+def test_model_config_as_model_field_raises():
+    with pytest.raises(PydanticUserError) as exc_info:
+
+        class MyModel(BaseModel):
+            model_config: str
+
+    assert exc_info.value.code == 'model-config-invalid-field-name'
+
+
+def test_dataclass_allowes_model_config_as_model_field():
+    config_title = 'from_config'
+    field_title = 'from_field'
+
+    @pydantic_dataclass(config={'title': config_title})
+    class MyDataclass:
+        model_config: dict
+
+    m = MyDataclass(model_config={'title': field_title})
+
+    assert m.model_config['title'] == field_title
+    assert getattr(m, '__pydantic_config__')['title'] == config_title