pep484 ORM / SQL result support

after some experimentation it seems mypy is more amenable
to the generic types being fully integrated rather than
having separate spin-off types.   so key structures
like Result, Row, Select become generic.  For DML
Insert, Update, Delete, these are spun into type-specific
subclasses ReturningInsert, ReturningUpdate, ReturningDelete,
which is fine since the "row-ness" of these constructs
doesn't happen until returning() is called in any case.

a Tuple based model is then integrated so that these
objects can carry along information about their return
types.  Overloads at the .execute() level carry through
the Tuple from the invoked object to the result.

To suit the issue of AliasedClass generating attributes
that are dynamic, experimented with a custom subclass
AsAliased, but then just settled on having aliased()
lie to the type checker and return `Type[_O]`, essentially.
will need some type-related accessors for with_polymorphic()
also.

Additionally, identified an issue in Update when used
"mysql style" against a join(), it basically doesn't work
if asked to UPDATE two tables on the same column name.
added an error message to the specific condition where
it happens with a very non-specific error message that we
hit a thing we can't do right now, suggest multi-table
update as a possible cause.

Change-Id: I5eff7eefe1d6166ee74160b2785c5e6a81fa8b95

1 files changed, 2 insertions, 14 deletions

diff --git a/lib/sqlalchemy/orm/base.py b/lib/sqlalchemy/orm/base.py
index 054d52d83..367a5332d 100644
--- a/lib/sqlalchemy/orm/base.py
+++ b/lib/sqlalchemy/orm/base.py
@@ -30,6 +30,7 @@ from ._typing import insp_is_mapper
 from .. import exc as sa_exc
 from .. import inspection
 from .. import util
+from ..sql import roles
 from ..sql.elements import SQLCoreOperations
 from ..util import FastIntFlag
 from ..util.langhelpers import TypingOnly
@@ -483,19 +484,6 @@ def _inspect_mapped_class(
         return mapper
 
 
-@inspection._inspects(type)
-def _inspect_mc(class_: Type[_O]) -> Optional[Mapper[_O]]:
-    try:
-        class_manager = opt_manager_of_class(class_)
-        if class_manager is None or not class_manager.is_mapped:
-            return None
-        mapper = class_manager.mapper
-    except exc.NO_STATE:
-        return None
-    else:
-        return mapper
-
-
 def _parse_mapper_argument(arg: Union[Mapper[_O], Type[_O]]) -> Mapper[_O]:
     insp = inspection.inspect(arg, raiseerr=False)
     if insp_is_mapper(insp):
@@ -691,7 +679,7 @@ class ORMDescriptor(Generic[_T], TypingOnly):
             ...
 
 
-class Mapped(ORMDescriptor[_T], TypingOnly):
+class Mapped(ORMDescriptor[_T], roles.TypedColumnsClauseRole[_T], TypingOnly):
     """Represent an ORM mapped attribute on a mapped class.
 
     This class represents the complete descriptor interface for any class