reorganize Mapped[] super outside of MapperProperty

We made all the MapperProperty classes a subclass
of Mapped[] to allow declarative mappings to name
Mapped[] on the left side.  this was cheating a bit because
MapperProperty is not actually a descriptor, and the mapping
process replaces the object with InstrumentedAttribute at
mapping time, which is the actual Mapped[] descriptor.

But now in I6929f3da6e441cad92285e7309030a9bac4e429d we
are considering making the "cheating" a little more extensive
by putting DynamicMapped / WriteOnlyMapped in Relationship's
hierarchy, which need a flat out "type: ignore" to work.

Instead of pushing more cheats into the core classes, move
out the "Declarative"-facing versions of these classes to be
typing only: Relationship, Composite, Synonym, and MappedSQLExpression
added for ColumnProperty.  Keep the internals expressed on the
old names, RelationshipProperty, CompositeProperty, SynonymProperty,
ColumnProprerty, which will remain "pure" with fully correct typing.
then have the typing only endpoints be where the "cheating"
and "type: ignores" have to happen, so that these are more or less
slightly better forms of "Any".

Change-Id: Ied7cc11196c9204da6851f49593d1b1fd2ef8ad8

1 files changed, 6 insertions, 6 deletions

diff --git a/lib/sqlalchemy/orm/clsregistry.py b/lib/sqlalchemy/orm/clsregistry.py
index dd79eb1d0..99a51c998 100644
--- a/lib/sqlalchemy/orm/clsregistry.py
+++ b/lib/sqlalchemy/orm/clsregistry.py
@@ -36,7 +36,7 @@ import weakref
 
 from . import attributes
 from . import interfaces
-from .descriptor_props import Synonym
+from .descriptor_props import SynonymProperty
 from .properties import ColumnProperty
 from .util import class_mapper
 from .. import exc
@@ -46,7 +46,7 @@ from ..sql.schema import _get_table_key
 from ..util.typing import CallableReference
 
 if TYPE_CHECKING:
-    from .relationships import Relationship
+    from .relationships import RelationshipProperty
     from ..sql.schema import MetaData
     from ..sql.schema import Table
 
@@ -350,7 +350,7 @@ class _GetColumns:
             if desc.extension_type is interfaces.NotExtension.NOT_EXTENSION:
                 assert isinstance(desc, attributes.QueryableAttribute)
                 prop = desc.property
-                if isinstance(prop, Synonym):
+                if isinstance(prop, SynonymProperty):
                     key = prop.name
                 elif not isinstance(prop, ColumnProperty):
                     raise exc.InvalidRequestError(
@@ -398,7 +398,7 @@ class _class_resolver:
     )
 
     cls: Type[Any]
-    prop: Relationship[Any]
+    prop: RelationshipProperty[Any]
     fallback: Mapping[str, Any]
     arg: str
     favor_tables: bool
@@ -407,7 +407,7 @@ class _class_resolver:
     def __init__(
         self,
         cls: Type[Any],
-        prop: Relationship[Any],
+        prop: RelationshipProperty[Any],
         fallback: Mapping[str, Any],
         arg: str,
         favor_tables: bool = False,
@@ -520,7 +520,7 @@ _fallback_dict: Mapping[str, Any] = None  # type: ignore
 
 
 def _resolver(
-    cls: Type[Any], prop: Relationship[Any]
+    cls: Type[Any], prop: RelationshipProperty[Any]
 ) -> Tuple[
     Callable[[str], Callable[[], Union[Type[Any], Table, _ModNS]]],
     Callable[[str, bool], _class_resolver],