Method _check_local_fields

django/db/models/base.py:2197–2273

(cls, fields, option)

    @classmethod
    def _check_local_fields(cls, fields, option):
        from django.db import models

        # In order to avoid hitting the relation tree prematurely, we use our
        # own fields_map instead of using get_field()
        forward_fields_map = {}
        for field in cls._meta._get_fields(reverse=False):
            forward_fields_map[field.name] = field
            if hasattr(field, "attname"):
                forward_fields_map[field.attname] = field

        errors = []
        for field_name in fields:
            try:
                field = forward_fields_map[field_name]
            except KeyError:
                errors.append(
                    checks.Error(
                        "'%s' refers to the nonexistent field '%s'."
                        % (
                            option,
                            field_name,
                        ),
                        obj=cls,
                        id="models.E012",
                    )
                )
            else:
                if isinstance(field.remote_field, models.ManyToManyRel):
                    errors.append(
                        checks.Error(
                            "'%s' refers to a ManyToManyField '%s', but "
                            "ManyToManyFields are not permitted in '%s'."
                            % (
                                option,
                                field_name,
                                option,
                            ),
                            obj=cls,
                            id="models.E013",
                        )
                    )
                elif isinstance(field, models.CompositePrimaryKey):
                    errors.append(
                        checks.Error(
                            f"{option!r} refers to a CompositePrimaryKey "
                            f"{field_name!r}, but CompositePrimaryKeys are not "
                            f"permitted in {option!r}.",
                            obj=cls,
                            id="models.E048",
                        )
                    )
                elif (
                    isinstance(field.remote_field, ForeignObjectRel)
                    and field not in cls._meta.local_concrete_fields
                    and len(field.from_fields) > 1
                ):
                    errors.append(