additional de-stringify pass for unions

the change in c3cfee5b00a40790c18d took out
a pass for de-stringify that broke some un-tested cases
for Optional with future annotations mode.   Adding tests
for this revealed that this was a subset of
a more general case where Union is presented
with ForwardRefs inside of it matching up within the type
map, which wasn't working before either, fixed that as well with
an additional de-stringify for elements within the Union.

Fixes: #8478
Change-Id: I8804cf6c67f14d10804584e1cddd2cfaa2376654

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/sqlalchemy/orm/properties.py b/lib/sqlalchemy/orm/properties.py
index 7d7175678..3d9fe578d 100644
--- a/lib/sqlalchemy/orm/properties.py
+++ b/lib/sqlalchemy/orm/properties.py
@@ -51,9 +51,11 @@ from ..sql.schema import Column
 from ..sql.schema import SchemaConst
 from ..util.typing import de_optionalize_union_types
 from ..util.typing import de_stringify_annotation
+from ..util.typing import de_stringify_union_elements
 from ..util.typing import is_fwd_ref
 from ..util.typing import is_optional_union
 from ..util.typing import is_pep593
+from ..util.typing import is_union
 from ..util.typing import Self
 from ..util.typing import typing_get_args
 
@@ -655,6 +657,9 @@ class MappedColumn(
         if is_fwd_ref(argument):
             argument = de_stringify_annotation(cls, argument)
 
+        if is_union(argument):
+            argument = de_stringify_union_elements(cls, argument)
+
         nullable = is_optional_union(argument)
 
         if not self._has_nullable:
@@ -690,6 +695,7 @@ class MappedColumn(
                 checks = (our_type,)
 
             for check_type in checks:
+
                 if registry.type_annotation_map:
                     new_sqltype = registry.type_annotation_map.get(check_type)
                 if new_sqltype is None: