1 files changed, 61 insertions, 1 deletions
diff --git a/lib/sqlalchemy/ext/mypy/util.py b/lib/sqlalchemy/ext/mypy/util.py
index 7079f3cd7..becce3ebe 100644
--- a/lib/sqlalchemy/ext/mypy/util.py
+++ b/lib/sqlalchemy/ext/mypy/util.py
@@ -1,18 +1,67 @@
 from typing import Optional
+from typing import Sequence
+from typing import Tuple
+from typing import Type
 
 from mypy.nodes import CallExpr
+from mypy.nodes import CLASSDEF_NO_INFO
 from mypy.nodes import Context
 from mypy.nodes import IfStmt
+from mypy.nodes import JsonDict
 from mypy.nodes import NameExpr
 from mypy.nodes import SymbolTableNode
+from mypy.nodes import TypeInfo
 from mypy.plugin import SemanticAnalyzerPluginInterface
+from mypy.plugins.common import deserialize_and_fixup_type
 from mypy.types import Instance
 from mypy.types import NoneType
-from mypy.types import Type
 from mypy.types import UnboundType
 from mypy.types import UnionType
 
 
+class DeclClassApplied:
+    def __init__(
+        self,
+        is_mapped: bool,
+        has_table: bool,
+        mapped_attr_names: Sequence[Tuple[str, Type]],
+        mapped_mro: Sequence[Type],
+    ):
+        self.is_mapped = is_mapped
+        self.has_table = has_table
+        self.mapped_attr_names = mapped_attr_names
+        self.mapped_mro = mapped_mro
+
+    def serialize(self) -> JsonDict:
+        return {
+            "is_mapped": self.is_mapped,
+            "has_table": self.has_table,
+            "mapped_attr_names": [
+                (name, type_.serialize())
+                for name, type_ in self.mapped_attr_names
+            ],
+            "mapped_mro": [type_.serialize() for type_ in self.mapped_mro],
+        }
+
+    @classmethod
+    def deserialize(
+        cls, data: JsonDict, api: SemanticAnalyzerPluginInterface
+    ) -> "DeclClassApplied":
+
+        return DeclClassApplied(
+            is_mapped=data["is_mapped"],
+            has_table=data["has_table"],
+            mapped_attr_names=[
+                (name, deserialize_and_fixup_type(type_, api))
+                for name, type_ in data["mapped_attr_names"]
+            ],
+            mapped_mro=[
+                deserialize_and_fixup_type(type_, api)
+                for type_ in data["mapped_mro"]
+            ],
+        )
+
+
 def fail(api: SemanticAnalyzerPluginInterface, msg: str, ctx: Context):
     msg = "[SQLAlchemy Mypy plugin] %s" % msg
     return api.fail(msg, ctx)
@@ -94,3 +143,14 @@ def _unbound_to_instance(
         )
     else:
         return typ
+
+
+def _info_for_cls(cls, api):
+    if cls.info is CLASSDEF_NO_INFO:
+        sym = api.lookup(cls.name, cls)
+        if sym.node and isinstance(sym.node, TypeInfo):
+            info = sym.node
+    else:
+        info = cls.info
+
+    return info